A METHOD OF PRODUCING DEHYDRATED FOOD PRODUCT HAVING LIGHT
COLOR WITH LESS BROWNING WHEN COMPARED WITH CONVENTIONAL FOOD
PRODUCT AND A CLOSED HYBRID DYNAMIC DEHYDRATION SYSTEM FOR
OBTAINING THE SAID DEHYDRATED FOOD PRODUCT
FIELD OF INVENTION
The present invention relates to a method of producing dehydrated food products having light color with less browning, when compared with conventional same food products, and having substantially same nutrional and vitamin values as that of natural food product. Further, the present invention comprises a closed hybrid dynamic dehydration system for obtaining the said food products to improve nutritional, storage and processing capabilities in an economical way.
BACKGROUND AND PRIOR ART
It is well known that variety of fruits and vegetables are produced by farming. Some of these fruits are consumed raw, and few are processed. Dried fruit is not only supplied for domestic market but also can be exported. In our country, large quantities of fruits and vegetables are wasted due to lack of proper post harvest storage facilities or processing capabilities. India is the second largest producer of fruits and vegetables, but unfortunately only 2% of the produce is processed leading to post harvest losses of more than 40%.
It is further known that drying is the oldest and simplest method of preserving food. According to Chou and Chua (2001), the degradation of food occurs mainly in three areas. Foods like fruits and vegetables consist of water, carbohydrate, protein and fractions of lipids. These compounds are easily modified in high temperature drying condition and result in degradation in food quality (Sokhansanj & Jayas, 1987). Consequently, the product's desirability for consumption is affected. Thus, use of the appropriate low temperature during drying is important..
Fruits and vegetables are currently dried through various means and equipments with an objective to improve shelf life, reduce packaging costs, lower shipping weights or storage space, enhance appearance, retain original flavor and maintain nutritional value. Product loses its moisture content during drying, which results in an increasing concentration of nutrients in the remaining mass. Hence, proteins, fats and carbohydrates are present in larger amounts per unit weight in the dried food than in the fresh.
Drying can never replace canning and freezing because these methods do a better job of retaining the taste, appearance and nutritive value of fresh food. But drying is a controlled

way to preserve foods that can add variety to meals and providing delicious & nutritious food products is the biggest challenge.
Various methods for drying have been determined by research and widespread experience. However, Home drying does not have firmly established procedure. Food can be dried in several ways, for example, by the sun if the air is hot and dry enough, or in an oven or dryer if the climate is humid.
With renewed interest in gardening and natural foods and because of the high cost of commercially dried products, drying foods at home is becoming popular again. Drying is not difficult, but it does take time and a lot of attention. Although there are different drying methods, the guidelines remain the same.
Although solar drying is a popular and very inexpensive method, it varies from place to place and also not necessary that each place has climate suitable for the same. Dependable solar dehydration of foods requires 3 to 5 consecutive days when the temperature is 95 degrees F. and the humidity is very low. Hence, solar drying is not a very feasible option. In addition, when the food products are exposed to solar drying, it may get contaminated with atmospheric contaminants and can be infected with microorganism such as fungus.
Drying food in the oven of a kitchen range, on the other hand, can be very expensive. In an electric oven, drying food has been found to be nine to twelve times costlier than canning. Food dehydrators are less expensive to operate but are only useful for a few months of the year. A convection oven can be the most economical investment if the proper model is chosen.
However, the mechanism of drying is a complex phenomenon involving combined heat and mass transfer and, in most cases, resulting in products with modified properties. Depending on the drying conditions, food products may undergo various degrees of browning, shrinkage, loss of nutrients, and so on.
Moreover, there are many factors which affect the drying method such as speed of drying, temperature, humidity,ventilation and uniform drying.
There are various existing equipments and devices available to perform drying operation .
Oven drying: Oven drying is the simplest way to dry food because you need almost no special equipment. It is also faster than sun drying. But oven drying can be used only on a small scale. Major disadvantages include high temperature drying, browning, nutrient loss, change in sensory properties, inferior product appearance due to shrinkage, change in textural properties, taste etc. In oven drying, energy consumption is high coupled with energy loss. The other demerits include uneven drying, higher space utilization, deactivation of desirable enzymes and higher chances of charring..
Microwave dryer: The demerits are very high energy cost, high nutrient loss during process, change in sensory properties, appearance, texture, taste, high energy consumption, higher space utilization, deactivation of desirable enzymes.
Vacuum dryer: The drawbacks are higher capital cost, higher energy cost, higher space requirement and deactivation of desirable enzymes.
Freeze dryer: The drawbacks are higher capital cost, high operational costs, . higher energy consumption, higher space utilization, deactivation of desirable enzymes.
Fluidized Bed dryer : The demerits are high capital cost, high operational cost, difficult to handle high bulk density products, lumps formations during drying.
Spray dryer The drawbacks are very high capital cost, very high energy consumption and can be used only for liquid materials..
Drum dryers are also utilized for high temperature drying causing higher browning, excessive nutrient loss, change in sensory properties, appearance, texture, taste etc. Due to high energy consumption, space utilization, low dehydration of the finished product and deactivation of desirable enzymes, such dryers are not providing satisfactory results.
To overcome the above-said problems and difficulties, the inventors are now proposed a
novel and inventive method of dehydrating the food products and a system to practice the
method.
In addition, looking at huge opportunities for processing of fruits and vegetables in India and
other countries, there is grave requirement to develop a method/ system / apparatus / device,
wherein dehydration of fruits and vegetables can be achieved. Preferably, the method and
system operate through high efficiency, low cost manner to give irresistibly high quality products.
Another challenge is that currently, there is an increased demand for convenient foods, which are expected to contain the minimum concentration of additives and preservatives. How one can minimize additives in food materials during drying and yet obtain the best quality, depends on method of producing, equipment and technology considerations. This creates challenges for the food industry and dryer manufactures with regard to the development of new technologies which can process temperature-sensitive materials and provide final products with high quality and improved physicochemical properties.
Therefore, in order to solve these technical problems, the inventors of the present invention propose a method and a closed hybrid dynamic dehydration system More particularly, a "Low temperature hybrid dryer (LTHD)", have been developed to satisfy most of the quality requirements. A LTHD can be operated over a wide range of temperatures, providing good conditions for the drying of heat sensitive materials.
OBJECTIVES OF THE INVENTION
The primary objective of the present invention is to provide a method of producing dehydrated food products having light color with less browning, when compared with conventional same food products, and having substantially same nutrional and vitamin values as that of natural food product. Another objective of the present invention is to provide a closed hybrid dynamic dehydration system wherein high efficiency, low cost, irresistibly high quality of the products are produced.
Another objective of the present invention is to provide dried products such as fruits or vegetables which retain physical, chemical and nutritional characteristics like that of natural fruits / vegetables, while having reduced amount of Acrylamide(AA).
SUMMARY OF THE INVENTION
The present invention relates to a method of producing dehydrated food products having light color with less browning, when compared with conventional same food products, and having substantially same nutrional and vitamin values as that of natural food product. . More particularly, a "Low temperature hybrid dryer (LTHD)", have been developed to satisfy most of the quality requirements. A LTHD can be operated over a wide range of temperatures,
providing good conditions for the drying of heat sensitive materials. The new closed hybrid dynamic dehydration system comprises three modes of drying i.e. due to temperature gradient (heat flow from high temperature to low temperature), convection and condensation mechanism to significantly reduce the problems like High cost, loss of nutrients in drying temperatures, shrinkage losses, burn injuries, reducing losses during processing, less/ no emissions, easy and operations friendly mechanism etc.
The expression light color with less browning means that the present product appears very closer to the color of the corresponding natural product and is much lighter in color when compared with corresponding products at the market. The products at the market are much more brown in color, when compared with the product of present invention.
BRIEF DESCRIPTION OF FIGURES
Figure 1 shows the low temperature hybrid dryer (LTHD) system according to the present invention.
Figure 2a and 2b shows LTHD system wherein dry zone, wet zone and material zone
and air draft is depicted according to the present invention. Figure 2a is a side
view of LTHD system and Figure 2b is a top view of the LTDH system.
Figure 3 shows the material zone depicting the platform/ tray according to the present
invention.
Figure 4 shows the material zone depicting the platform/ tray as one of the embodiment of
the present invention.
Figure 5 shows the material zone depicting the platform/ tray as one of the embodiment of
the present invention for drying green peas.
Figure 6 shows LTHD system operation according to the present invention, wherein water
recovery is shown.
Figure 7 shows conventionally dried banana chips and LTHD dried and fried (30% less
oils) banana chips.
Figure 8 shows conventionally dried Apple Chips and LTHD dried Apple chips.
Figure 9 shows LTHD dried chips pellets and storing in bulk bag.
Figure 10 shows comparison of conventional fried potato chips and LTHD dried and fried
Potato Chips.
BRIEF DESCRIPTION OF TABLES
Table 1 shows comparison of physical, chemical and Nutritional characteristics of dried product according to the present invention and conventional drying.
Table 2 shows physical, chemical, Nutritional, microbiological and Organoleptic characteristics of dried product (Banana chips) according to the present invention.
Table 3 shows physical, chemical, Nutritional, microbiological and Organoleptic characteristics of dried product (Apple chips) according to the present invention.
Table 4 shows physical, chemical, Nutritional, microbiological and Organoleptic characteristics of dried product (Potato chips) according to the present invention.
Table 5 shows physical, chemical, Nutritional, microbiological and Organoleptic characteristics of dried product (Beet root chips) according to the present invention.
Table 6 shows the comparison of Acrylamide level in the dried product according to the present invention and conventional (regular) dried and fried products.
Table 7a and 7b shows the heat load calculation in conventional process of drying the fruits and vegetables and according to the present invention, respectively.
It is noted that the above-said physical, chemical and nutrional parameters are tested out as per the standards of "Association of official analtic chemist (AOC)". The equipments and testing conditions are set out as prescribed in the AOC standard. DETAIL DESCRIPTION OF THE INVENTION
Accordingly, the present invention relates to a method of producing dehydrated food products having light color with less browning, when compared with conventional same food products, and having substantially same nutrional and vitamin values as that of natural food product, said method comprising the steps of
a. obtaining cut or sliced raw food product,
b. blanching or soaking the product of step (a) at a temperature 70 to 80°C, and
treating the same with chemicals such as herein described,
c. dehydrating the product of step (b) in closed dynamic manner at a temperature
in the range of 35°C to 60°C for a time period in the range of 3 to 6 hours, at
above atmospheric pressure to obtain the product having water content 1.5 to
4.0% and crispy texture.
Yet another aspect of the present invention provides the food products which are preferable dehydrated fruits or vegetables.
Yet another aspect of the present invention relates to dehydrated fruit apple, banana, figs, grapes, pineapple, jack fruit etc.
Further aspect of the present invention relates to providing dehydrated vegetables selected
from potato, onion, green peas, beet root, carrot, ladies finger, pumpkins etc.
Yet another aspect of the present invention, wherein in step (b) chemicals used are
selected from the group comprising sodium metasulphite, calcium chloride, sodium
chloride, or KMS solution
One more aspect aspect of the present invention, wherein in step (c) the relative humidity
is maintained in the range of 5 to 80 %.
Yet another aspect of the present invention, wherein the product of step (c) is optionally
frying at a temperature in the range of 140-180°C for 2 to 15 minutes and/ or adding
spices or any flavoring agents.
Yet another aspect of the present invention, wherein the dehydrated food product is in the
shape of chips, fingers, triangular, circular, oval, rectangular, square, star shape or any
combination thereof.
Yet another aspect of the present invention relates to a method of producing dehydrated
food products having light color with less browning, when compared with conventional
same food products, and having substantially same nutrional and vitamin values as that of
natural apple, said method comprising the steps of
a. obtaining cut or sliced raw apple product in any desired shape,
b. blanching the product of step (a) at a temperature 60°C to 70°C for 30 to 50
seconds, and soaking in a solution containing 0.05 to 0.2 % sodium
metasulphite, 3 to 10 % sugar and .02 to 0.9 calcium chloride,
c. dehydrating the product of step (b) in closed dynamic manner at a temperature
in the range of 40 to 65°C for a time period in the range of 3 to 6 hours, at
above atmospheric pressure to obtain the product having water content 1.5 to
3.0% and crispy texture.
Yet another aspect of the present invention, wherein in step (b) the blanching is carried
out at a temperature 65°C for 45 seconds and soaking in a solution containing 0.1 %
sodium metasulphite, 6 % sugar and 0.5 % calcium chloride.
Yet another aspect of the present invention, wherein in step (c) dehydrating is carried out
of the product of step (b) in closed dynamic manner at a temperature in the range of 50 C
for a time period in the range of 4.5 to 5 hours, and at above atmospheric pressure to
obtain the product having water content 1.5 to 3.0% and crispy texture.
Yet another aspect of the present invention, wherein the apple product is in the shape of
chips, fingers, triangular, circular, oval, rectangular, square, star shape or any
combination thereof.
Yet another aspect of the present invention, wherein the apple product has 8 to 15 times higher crispy texture and retains substantially same Beta Carotene value, when compared with conventional dried apple chips.
Yet another aspect of the present invention, wherein a method of producing dehydrated food product banana having light color with less browning, when compared with conventional same food products, and having substantially same nutrional and vitamin values as that of natural food product as that of natural banana, said method comprising the steps of
a. obtaining cut or sliced raw banana product in any desired shape,
b. soaking the product of step (a) in a solution containing 0.05 to 0.2 % sodium
metasulphite, 02 to 0.9 calcium chloride and 0.1 to 0.9 % salt.
c. dehydrating the product of step (b) in closed dynamic manner at a temperature
in the range of 40 to 65°C for a time period in the range of 3 to 6 hours, and at
above atmospheric pressure to obtain the product.
Yet another aspect of the present invention, wherein in step (b) the soaking is carried out at a temperature 65°C for 45 seconds in a solution containing 0.2 % sodium metasulphite, 0.5 % calcium chloride and salt 0.2 %.
Yet another aspect of the present invention, wherein in step (c) dehydrating is carried out the product of step (b) in closed dynamic manner at a temperature in the range of 50 C for a time period in the range of 3 to 3.5 hours, at above atmospheric pressure to obtain the product.
Yet another aspect of the present invention, wherein the dehydrated banana product is in the shape of chips, fingers, triangular, circular, oval, rectangular, square, star shape or any combination thereof.
Yet another aspect of the present invention, wherein the dehydrated banana product has 2 to 10 times higher crispy texture when compared with conventional dried banana chips. Yet another aspect of the present invention, relates to a method of producing dehydrated food product potatoes having light color with less browning, when compared with conventional same food products, and having substantially same nutrional and vitamin values as that of natural food product as that of natural potatoes, said method comprising the steps of
a. obtaining cut or sliced raw potatoes product in any desired shape,
b. blanching the product of step (a) at a temperature 75°C to 100°C for 10 to 50
minutes, soaking in a solution containing 0.05 to 5 % sodium chloride, and
dipping in 0.1 to 5.0 % KMS solution for 5 to 30 minutes,
c. dehydrating the product of step (b) in closed dynamic manner at a temperature
in the range of 40 to 65°C for a time period in the range of 3 to 6 hours, and at
above atmospheric pressure to obtain the product having water content 1.5 to
3.0% and crispy texture.
Yet another aspect of the present invention, wherein wherein in step (b) the blanching is
carried out at a temperature 93 to 95°C for 10 minutes, thereafter soaking in a solution
containing 2.0 % sodium chloride, and dipping in 0.2 % KMS solution for 10 minutes.
Yet another aspect of the present invention, wherein in step (c) dehydrating the product of
step (b) in closed dynamic manner at a temperature in the range of 50°C for a time period
in the range of 3 to 3.5 hours, at above atmospheric pressure to obtain the product having
water content 1.5 to 3.0% and crispy texture.
Yet another aspect of the present invention, wherein the potato product is in the shape of
chips, fingers, triangular, circular, oval, rectangular, square, star shape or any
combination thereof.
Yet another aspect of the present invention, wherein the potato product having
rehydration ratio in the range of 3: 1 to 6:1.
Yet another aspect of the present invention, wherein the potato product having 8 to 15
times higher crispy texture, when compared with conventional dried potato chips.
Yet another aspect of the present invention, relates to a method of producing dehydrated
food product beet root having light color with less browning, when compared with
conventional same food products, and having substantially same nutrional and vitamin
values as that of natural food productas that of natural beet root, said method comprising
the steps of
d. obtaining cut or sliced raw beet root product in any desired shape,
e. blanching the product of step (a) at a temperature 75°C to 100°C for 2 to 10
minutes, dipping in a solution containing 0.05 to 5 % calcium chloride, and 3
to 10 % sugar and 0.1 to 8 % salt for 5 to 30 minutes,
f. dehydrating the product of step (b) in closed dynamic manner at a temperature
in the range of 40 to 65°C for a time period in the range of 3 to 6 hours, and at
above atmospheric pressure to obtain the beet root product.
Yet another aspect of the present invention, wherein in step (b) the blanching is carried
out at a temperature 80°C for 3 to 4 minutes, dipping in a solution containing 0.5%
calcium chloride, 5 % sugar and 0.4 % salt for 15 minutes.
Yet another aspect of the present invention, wherein in step (c) dehydrating the product of
step (b) in a closed dynamic manner at a temperature in the range of 50°C for a time
period in the range of 3 to 3.5 hours, and at above atmospheric pressure to obtain the
product having water content 1.5 to 3.0% and crispy texture.
Yet another aspect of the present invention, wherein the beet root product is in the shape
of chips, fingers, triangular, circular, oval, rectangular, square, star shape or any
combination thereof.
Yet another aspect of the present invention, wherein the beet root product having 1.5 to 8
times higher crispy texture, when compared with conventional dried beet root product.
Yet another aspect of the present invention, wherein the light color with less browning
dehydrated food products prepared by a method as claimed in any of the preceding
claims.
Yet another aspect of the present invention, wherein the light color with less browning,
dehydrated food product apple chips produced by a method, wherein the product is apple
chips.
Yet another aspect of the present invention, wherein the light color with less browning,
dehydrated food product apple chips, having 8 to 15 times higher crispy texture and retain
substantially same Beta Carotene value, when compared with conventional dried apple
chips.
Yet another aspect of the present invention, wherein the light color with less browning,
dehydrated food product produced by a method wherein the product is banana chips.
Yet another aspect of the present invention, wherein the light color with less browning,
dehydrated food product banana, having 8 to 15 times higher crispy texture, when
compared with conventional dried and fried banana chips.
Yet another aspect of the present invention, wherein the light color with less browning,
dehydrated food product banana produced by a method wherein the product is potatoes
chips.
Yet another aspect of the present invention, wherein the light color with less browning,
dehydrated food products potato, wherein the dried and fried potato chips having acryl
amide content reduced to 5 to 15 times, when compared with conventional fried potatoes
chips.
Yet another aspect of the present invention, wherein the light color with less browning,
dehydrated food products, wherein the potatoes chips have 20 to 50 % reduced oil content
after frying.
Yet another aspect of the present invention, wherein the light color with less browning
dehydrated food product produced by above method, wherein the product is beet root
chips.
Yet another aspect of the present invention, wherein the light color with less browning
dehydrated food product wherein the beet root chips having 2 to 3 time higher crispy
texture and 0.8 to 1.0 times higher protein digestibility index, when compared with
conventional dried beet root chips.
Accordingly, the present invention relates to a closed hybrid dynamic dehydration system, the
said system as (shown in Figure 2) comprises of a wet zone (2), wherein first heat-exchanger
pipes (4) (cooling tube) - serpentine or coiled set of pipes are placed inside the wet zone, the
said coiled pipes are operatively coupled with a fan (6a), which is collecting the hot air and
passing the collected air over second heat exchanger (5) (heating coils),
a dry zone (1), wherein second heat-exchanger pipes (heating tube)- serpentine or coiled set
of pipes are placed inside the said dry zone (1), the said coiled pipes are also operatively
coupled with a fan (6b), which is collecting the cool air and passing over the heating coils (5),
a material zone (3), whereby the food is kept for drying, the said material zone (3) is
connecting the dry zone (1) and wet zone (2) of the said dehydration system by means of
separation wall (7a & 7b), respectively. The said separation wall comprising converging
holes so as to create sufficient pressure difference across the separation wall 7a & 7b and hot
air from dry zone (1) passing over the food, drying the food by controlling the moisture and
humidity level, and passing to the wet zone (2),
the said heat-exchanging pipes(4 and 5) are carrying refrigerant liquid inside the pipes and
connected by means of expansion device (20) and compressor (21) and the all said
components are enclosed in a close chamber.
One aspect of the invention wherein the wet zone comprising the temperature in the range of
10 Degree C to 70 Degree C, and relative humidity in the range of 05 to80 % RH.
Another aspect of the present invention wherein the dry zone comprising the temperature in
the range of 10°C to 60°C, and relative humidity in the range of 05 to80 % RH
Yet another aspect of the present invention, wherein there are controlling means to control
the speed of the fan, thereby controlling the rate of drying of the food.
Yet another aspect of the present invention, wherein the said system comprising optional
heating means.
Yet another aspect of the present invention, wherein a display panel is provided, whereby the
details i.e. temperature, relative humidity, weight change during drying, moisture loss
dehydration curve etc are displayed and the desired level of operational parameters will be set
out.
Yet another aspect of the present invention, wherein the material zone is having platform
placed horizontal or inclined position on one or more load cells.
Another aspect of the present invention, wherein the said platforms/ tray (8) are having
perforations (12) so that food placed on them get maximum exposure with air.
Another aspect of the present invention, wherein the platforms / trays (8) comprises of
contours (as shown Figure 3), so that food pieces do not fall down.
Yet another aspect of the present invention, wherein the water drops collected in the wet zone
is taken out by providing outlet in the wet zone (as shown Figure 6), thereby reducing the
moisture level in the circulated air inside the chamber.
Another aspect of the present invention, wherein one or more motorized valves (11) are
placed on the top of the said chamber in order to release the excess pressure inside the
chamber.
Another aspect of the present invention, wherein sensors (9) are placed at various zones of
the chamber, and coupled to the display panel (30).
The said system comprising salient features of the LTHD, wherein separation of water verses
evaporation of water in other conventional system, low temperature drying is carried out
approximately in the range of 10-60°C. Therefore, latent heat recovery is upto the extent of
60-80%. Hence, there is significantly low cost processing of foods. In the present system due
to low volatile component loss during processing, the authenticity is maintained during
drying at lower temperature. Further, the present system has better efficiency, reduces C02
emissions and can be applied to large scale batch as well as continuous process. Therefore the
process is environment friendly.
Condensation refers to a process in which moisture is getting separated by creating
temperature and humidity difference. Unique equipment is designed by creating air draft and
along with temperature and humidity difference. For research and development purpose,
special sensors for measuring humidity and temperature at various stages of air cycle are
installed. For monitoring of moisture loss during drying, load cell with digital analog is
provided. Three distinct regions that constitute in equipment are Low RH area, High RH
Area.
For providing the final texturing properties, heaters are provided which automatically
getactivated after advanced stage of drying. (Optional process as per requirement of drying
process).
Fruits & vegetable generally contain water up to 80% to 90%. As system believes in
separation of water & not evaporation of water, good quality water can be generated,
therefore it can create water conservation initiatives.
The lower processing temperature results in a lighter color for the dried product bringing in
higher market value. It reduces brown spots, a dark band formed 1 - 2 mm below the surface
in high temperature drying. A reduced brown spot, in turn, reduces post-drying processing
costs and product wastage.
Browning of foods can occur by enzymatic and non-enzymatic (Maillard) reactions, which
usually impairs the sensory properties of products due to the associated changes in colour,
flavour and texture and the nutritional properties. Enzymatic browning requires four
components namely oxygen, enzyme, copper and a substrate. The present system is a closed
loop system and hence an inert atmosphere can be created in the system.
Factors that influence food quality during drying
(Table Removed)
Present (LTHD) improves food qualities vis-a-vis conventional drying or frying operations,
as shown in tables 1 to 6.
Present (LTHD) consumes 50% less energy than conventional oven dryers by operating at
lower temperature, as shown in table 7a and 7b.
For onion slices dried in the LTHD, there was an energy saving of about 30%, with better
product quality, when compared with conventional dryers. It was observed that dried apples
showed excellent color and retention of vitamin A, and the overall quality of the dried
product was very high. The objective of this paper was to investigate the color, porosity,
texture and re-hydration characteristics of potato, apple, banana, beet root, guava and dried
vegetables. Freeze drying and vacuum drying experiments were also conducted in order to
make a comparison with LTHD dried samples.
The dehydration of the food products are carried out in a closed dynamic manner. The closed dynamic manner means, the food products are dehydrated at a low temperature which can vary over a wide range of temperatures, providing good conditions for the drying of heat sensitive materials and producing dehydrated food products having light color with less browning, when compared with conventional same food products, and having substantially same nutrional and vitamin values as that of natural food product. The new closed hybrid dynamic dehydration method comprises three modes of drying i.e. the first being temperature gradient drying (heat flow from high temperature to low temperature), the second mode is convection and the third mode is condensation mechanism to significantly reduce the problems like high cost, loss of nutrients in drying temperatures, shrinkage losses, burn injuries, reducing losses during processing, less/ no emissions, easy and operations friendly mechanism etc. The expression "low temperature" means a temperature which is not exceeding 60°C and preferably being in the range of 35°C to 60°C, and most preferably between 35°C to 50°C. If the temperature is kept lower than the dehydration time is prolonged and it also depends on the nature of food product to be dehydrated, for e.g. if more succulent / water born fruits or vegetables such as pumpkin, pineapple, etc. take more time than to dehydrate than fruits and vegetables having less water content such as carrot, apple, potatoes. Therefore, it is within the skills of an expert to select the duration, other conditions for a particular kind of fruit or vegetable.
The dehydration step is performed in a closed dynamic manner which means, the food is exposed to low temperature hot air at above atmospheric pressure conditions. However, the said atmospheric pressure is not allowed to be exceeding beyond a particular level, hence one or more motorized valves are placed on the top of the chamber in order to release any excess pressure inside the chamber. The food product is treated in a closed dynamic system without exposing the food product to a fresh atmosphere air, instead the heating medium such as air is circulated within the enclosed chamber, wherein the food product to be dehydrated is in contact with hot air.
To implement the above-said method, a closed hybrid dynamic dehydration system is developed. The said system utilizes the three modes of heating such as due to temperature gradient (heat flow from high temperature to low temperature), convection and condensation mechanism; hence it is called as hybrid system. The air flow from one zone to another zone is created due to air pressure difference exist between various zones of the system and that is the reason the method / system are called dynamic method / system. The said system
comprising a material zone (3), whereby the food is kept for dehydrating the said material zone (3) is connecting the dry zone (1) and wet zone (2) of the said dehydration system by means of separation wall (7a & 7b), respectively. The said separation wall comprising converging holes so as to create sufficient positive pressure difference across the separation wall 7a & 7b and hot air from dry zone (1) passing over the food, drying the food by controlling the moisture and humidity level, and passing to the wet zone (2).
The expression light color with less browning means that the present product appears very closer to the color of the corresponding product and is much lighter in color when compared with corresponding products at the market. The products at the market are much more brown in color, when compared with the product of present invention.
Present studies on quality improvements:
a) Usage of inert atmosphere to improve appearance of the products.
Apple, Banana, Beet root, guava and potato were selected, because they tend to brown easily due to oxidation. In order to eliminate oxygen, lemon juice and peel were chosen as natural inhibitors of browning for air drying of apple.
b) Materials and methods
Sample preparation : Apples, bananas, beet, carrot were purchased from a local supermarket. The materials were cut into 120 thou thick slices, then immediately immersed in water at room temperature to prevent contact with oxygen, and wash away phenolic compounds and free enzymes from the cut surfaces, thus avoiding oxidation. The preparation was done as soon as possible, which was no longer than 10 min. When using lemon juice as a natural inhibitor of browning for air dried samples, the seeds were removed; the squeezed lemon juice was diluted with water to concentrations of 10%, 30%, and 50%. A second soaking-agent was prepared by blending 10 g of lemon peel with 150 ml of distilled water and then filtered. The filtrate was used as the soaking agent. Approximately 100 g of sample was immersed in 150 ml of the soaking solution for 30 min before air drying.
c) LTHD drying can be attached with modified atmosphere dryer : The intent of the
present experiment is to use carbon dioxide/ nitrogen as inert gas. A food tray mounted on a
load cell would be placed in the drying chamber. The drying temperature inside the chamber
was measured by T type thermocouple, which is inserted in the middle position of the inlet
cross section. Temperature sensors are installed to monitor the temperature change within the
drying chamber. The weight change of samples was continuously monitored by a load cell. All the data can be collected by data logger.
d) Checking for surface porosity
A scanning electron microscope would be used to investigate the surface porosity of the dried food samples. The SEM captures detailed three-dimensional images at magnifications ranging from 15 to 200,000 with a resolution of 5 nm. In this study, samples would be examined for each drying method and the one that showed the surface porosity clearly was selected.
e) Shrinkage
During drying, there is a change in volume of samples as it loses water to die drying medium. The change in volume, called shrinkage, would be measured with respect to its initial volume.
f) Texture analysis
A stable Micro System texture analyzer (model TA.XT2i, Godalming, Surry, UK) would be used to check hardness of the samples. Probe would be selected as per the size of the sample and guide line provided in users manual. Only a compression test is to be conducted in this study.
g) Rehydration studies
A constant temperature water bath which can maintain the temperature from 30 to 100 Degree C was used in re-hydration experiments. The experiment was conducted at 60 and 80°C. Each bone dried sample was weighed first, placed in a tea drainer and then immersed in the water bath for various lengths of time. At different time intervals, the samples were removed from the water; excess water from the surfaces gently wiped off using tissues and weighed. The accuracy of balance is 0.0001g. Each experimental run was performed in triplicate. The mean values of weight of absorbed water for a given re-hydration period were recorded.
h) LTHD drying has higher energy efficiency because of the latent heat recovery and lower energy consumption for each unit of water removed; excellent control of the environment for high value products; consistent output of product and the closed system makes it possible to use inert gas.
The inventors have conducted experiments and results are compared with conventional drying, wherein various parameters such as drying environment, drying temperature, surface porosity, shrinkage, color, flavor, texture are analyzed. Further, inventors have conducted experiments, whereby the food quality by drying according to the present invention is
compared with conventional drying. The trials were carried out with various fruits and vegetables.
Using the above principle, inventors designed and got one working unit fabricated in India. The photo of the unit is shown below in figure 1. This unit is a batch process unit and is able to dry approx. 3-4 kg of the raw materials per cycle. However, it is within the purview of the person skilled in the art to implement the system as continuous process unit on large scale.
Series of trials have been conducted using this technology to demonstrate the products for significant consumer benefits. The system is able to process table grade potatoes to deliver significantly superior quality product and will be able to address Agro related quality issues and seasonality of the potatoes, while delivering significant competitive advantage to the business. The photographs shown in figures 7 to 10 demonstrate the benefit of the present invention in comparison to the frying of the chips from the same quality potatoes.
Example 1 (flow chart of preparation of ripe apple chips)
Example 2 (flow chart of preparation of unripe bananas chips)
Example 3 (flow chart of preparation of raw potatoes)
Example 4 (preparation of beet root chips)
(Formula Removed)
In addition to the above-said illustration, the present LTHD systems also help in reducing the level of Acrylamide (AA) level in the potato chips. The sample analyzed by PepsiCo Beaumont Park analytical facility has confirmed AA level for the chips processed using this technology to be at < 50 ppb as shown in TABLE 6.
The present invention having advantages outlined above, is just not limited only to potato chips. This can be very well used for production of other fruits and veggie chips like banana, apple, pineapple, sapota chips. (Fig 7 to 10). These chips can be produced at much lower oil content than any other conventional processing technologies (5%-20% oil for HDLT chips vs 35% oil) to make truly healthier products.
The present invention also helps in reducing lesser carbon footprint as water is evaporated from the potatoes at much lower temperature without using the latent heat of evaporation. Further, the storage problem on potatoes can be effectively resolved with the storage of Dried Potato (or Fruit/ Veggie Chips) pellets. The picture of the dried potato pellets for storage in shown in Fig 9 which can be further cooked using Frying or Microwave technology. This also provides significant opportunity to use the dried potatoes pellets as a potential on-premises solution.
ADVANTAGES OF THE INVENTIONS
a) In the present system significant high quality dehydrated fruit and vegetable products are produced.
b) In the present system, prototypes of pro-biotic solutions i.e. curd powders, aloevera powder etc can be produced.
c) The present system is an energy efficient system as it is based upon latent heat conservation.
d) The present system is a low cost version with respect to frying and conventional drying.
e) The present system is providing better quality at lower cost than proven freeze dried products.
f) Separation of water verses evaporation of water in other conventional system.
g) In the present system, low temperature drying is carried out approximately in the range of 10-60°C. Therefore, latent heat recovery up to the extent of 60-80%. Hence, there is significantly low processing cost of foods.
h) In the present system there is low volatile component loss during processing and
hence the authenticity is maintained during drying at lower temperature, i) The present system has better efficiency, reduces CO2 emissions and can be applied
to large scale batch as well as continuous process, j) Technically, the present apparatus is proved to be most cost effective model. There
are latent heat recovery benefits, as the system works on separation of water and not
evaporation, k) In the present invention, low temperature drying help retaining most of the nutrients
in the products. 1) In the present apparatus, there are unique air circulations, which help in drying at
accelerated speed, m) The apparatus of the present invention can be interlinked with other food processing
methods to deliver consumer benefits, n) The drying process according to the present invention is unique, and can have
multiple advantages ( varied products/ different products). 0) The products produced, according to the present invention are excellent in
appearance, texture and re-hydration characteristics.
P)
q) The apparatus and process of the present invention is also helpful in reducing acrylamide formation in food. The advantages of the disclosed invention are thus attained in an economical, practical, and facile manner. While preferred aspects and example configurations have been demonstrated, further it is to be understood that various further modifications and additional configurations will be apparent to those skilled in the art. It is intended that the specific embodiments and configurations herein disclosed are illustrative and there is further experimentation is going on for best practicing the invention, and hence, it should not be interpreted as limitations on the scope of the invention.

WE CLAIM:
1. A method of producing dehydrated food products having light color with less
browning, when compared with conventional same food products, and having
substantially same nutrional and vitamin values as that of natural food product, said
method comprising the steps of
a. obtaining cut or sliced raw food product,
b. blanching or soaking the product of step (a) at a temperature 70 to 80°C, and
treating the same with chemicals such as herein described,
c. dehydrating the product of step (b) in closed dynamic manner at a temperature
in the range of 35 C to 60°C for a time period in the range of 3 to 6 hours, at
above atmospheric pressure to obtain the product having water content 1.5 to
4.0% and crispy texture.
2. The method as claimed in claim 1, wherein in the food products are preferable fruits or vegetables.
3. The method as claimed in claim 2, wherein the fruit is apple, banana, beet root, sapota, pineapple, figs, grapes or jack fruit.
4. The method as claimed in claim 2, wherein the vegetable is potato, onion or, green peas.
5. The method as claimed in claim 1, wherein in step (b) chemicals are selected from the group comprising sodium metasulphite, calcium chloride, sodium chloride, or KMS solution
6. The method as claimed in claim 1, wherein in step (c) the relative humidity is maintained in the range of 5 to 80 %.
7. The method as claimed in claim 1, wherein the product of step (c) is optionally frying at a temperature in the range of 140-180°C for 2 to 15 minutes and/ or adding spices or any flavoring agents.
8. The method as claimed in claim 1, wherein the product is in the shape of chips, fingers, triangular, circular, oval, rectangular, square, star shape or any combination thereof.
9. A method of producing light color with less browning, dehydrated Apple product having substantially same nutrional and vitamin values as that of natural apple, said method comprising the steps of
a. obtaining cut or sliced raw apple product in any desired shape,

b. blanching the product of step (a) at a temperature 60°C to 70°C for 30 to 50
seconds, and soaking in a solution containing 0.05 to 0.2 % sodium
metasulphite, 3 to 10 % sugar and .02 to 0.9 calcium chloride,
c. dehydrating the product of step (b) in closed dynamic manner at a temperature
in the range of 40 to 65°C for a time period in the range of 3 to 6 hours, at
above atmospheric pressure to obtain the product having water content 1.5 to
3.0% and crispy texture.
10. The method as claimed in claim 9, wherein in step (b) the blanching is carried out at a temperature 65°C for 45 seconds and soaking in a solution containing 0.1 % sodium metasulphite, 6 % sugar and 0.5 % calcium chloride.
11. The method as claimed in claim 9, wherein in step (c) dehydrating is carried out of the product of step (b) in closed dynamic manner at a temperature in the range of 50°C for a time period in the range of 4.5 to 5 hours, and at above atmospheric pressure to obtain the product having water content 1.5 to 3.0% and crispy texture.
12. The method as claimed in claim 9 to 11, wherein the product is in the shape of chips, fingers, triangular, circular, oval, rectangular, square, star shape or any combination thereof.
13. The method as claimed in claim 9 to 12, wherein the product has 8 to 15 times higher crispy texture and retains substantially same Beta Carotene value, when compared with conventional dried apple chips.
14. A method of producing dehydrated food product having light color with less browning, when compared with conventional same food products, and having substantially same nutrional and vitamin values as that of natural food product as that of natural banana, said method comprising the steps of
a. obtaining cut or sliced raw banana product in any desired shape,
b. soaking the product of step (a) in a solution containing 0.05 to 0.2 % sodium
metasulphite, 02 to 0.9 calcium chloride and 0.1 to 0.9 % salt.
c. dehydrating the product of step (b) in closed dynamic manner at a temperature
in the range of 40 to 65°C for a time period in the range of 3 to 6 hours, and at
above atmospheric pressure to obtain the product.
15. The method as claimed in claim 14, wherein in step (b) the soaking is carried out at a
temperature 65°C for 45 seconds in a solution containing 0.2 % sodium metasulphite,
0.5 % calcium chloride and salt 0.2 %.

16. The method as claimed in claim 14, wherein in step (c) dehydrating is carried out the product of step (b) in closed dynamic manner at a temperature in the range of 50°C for a time period in the range of 3 to 3.5 hours, at above atmospheric pressure to obtain the product.
17. The method as claimed in claim 14 to 16, wherein the product is in the shape of chips, fingers, triangular, circular, oval, rectangular, square, star shape or any combination thereof.
18. The method as claimed in claim 14 to 17, wherein the product has 2 to 10 times higher crispy texture when compared with conventional dried banana chips.
19. A method producing dehydrated food products having light color with less browning, when compared with conventional same food products, and having substantially same nutrional and vitamin values as that of natural food product as that of natural potatoes, said method comprising the steps of
a. obtaining cut or sliced raw potatoes product in any desired shape,
b. blanching the product of step (a) at a temperature 75°C to 100°C for 10 to 50
minutes, soaking in a solution containing 0.05 to 5 % sodium chloride, and
dipping in 0.1 to 5.0 % KMS solution for 5 to 30 minutes,
c. dehydrating the product of step (b) in closed dynamic manner at a temperature
in the range of 40 to 65°C for a time period in the range of 3 to 6 hours, and at
above atmospheric pressure to obtain the product having water content 1.5 to
3.0% and crispy texture.
20. The method as claimed in claim 19, wherein in step (b) the blanching is carried out at a temperature 93 to 95°C for 10 minutes, thereafter soaking in a solution containing 2.0 % sodium chloride, and dipping in 0.2 % KMS solution for" 10 minutes.
21. The method as claimed in claim 19, wherein in step (c) dehydrating the product of step (b) in closed dynamic manner at a temperature in the range of 50°C for a time period in the range of 3 to 3.5 hours, at above atmospheric pressure to obtain the product having water content 1.5 to 3.0% and crispy texture.
22. The method as claimed in claim 19 to 21, wherein the product is in the shape of chips, fingers, triangular, circular, oval, rectangular, square, star shape or any combination thereof.
23. The method as claimed in claim 19 to 22, wherein the product having rehydration ratio in the range of 3: 1 to 6:1.

24. The method as claimed in claim 19 to 22, wherein the product having 8 to 15 times higher crispy texture, when compared with conventional dried potato chips.
25. A method of producing dehydrated food products having light color with less browning, when compared with conventional same food products, and having substantially same nutrional and vitamin values as that of natural food product as that of natural beet root, said method comprising the steps of
a. obtaining cut or sliced raw beet root product in any desired shape,
b. blanching the product of step (a) at a temperature 75°C to 100°C for 2 to 10
minutes, dipping in a solution containing 0.05 to 5 % calcium chloride, and 3
to 10 % sugar and 0.1 to 8 % salt for 5 to 30 minutes,
c. dehydrating the product of step (b) in closed dynamic manner at a temperature
in the range of 40 to 65°C for a time period in the range of 3 to 6 hours, and at
above atmospheric pressure to obtain the beet root product.
26. The method as claimed in claim 25, wherein in step (b) the blanching is carried out at a temperature 80 C for 3 to 4 minutes, dipping in a solution containing 0.5% calcium chloride, 5 % sugar and 0.4 % salt for 15 minutes.
27. The method as claimed in claim 25, wherein in step (c) dehydrating the product of step (b) in a closed dynamic manner at a temperature in the range of 50°C for a time period in the range of 3 to 3.5 hours, and at above atmospheric pressure to obtain the product having water content 1.5 to 3.0% and crispy texture.
28. The method as claimed in claim 25 to 27, wherein the product is in the shape of chips, fingers, triangular, circular, oval, rectangular, square, star shape or any combination thereof.
29. The method as claimed in claim 25 to 28, wherein the product having 1.5 to 8 times higher crispy texture, when compared with conventional dried beet root product.
30. The light color with less browning, dehydrated food products prepared by a method as claimed in any of the preceding claims.
31. The light color with less browning, dehydrated food product produced by a method as claimed in claim 9 to 13, wherein the product is apple chips.
32. The light color with less browning dehydrated food products as claimed in claims 9 to 13, is apple chips.
33. The light color with less browning, dehydrated food product as claimed in claim 32, having 8 to 15 times higher crispy texture and retain substantially same Beta Carotene value, when compared with conventional dried apple chips.

34. The light color with less browning, dehydrated food product produced by a method as claimed as claimed in claim 14 to 18, wherein the product is banana chips.
35. The light color with less browning, dehydrated food product as claimed in claim 14 to 18, having 8 to 15 times higher crispy texture, when compared with conventional dried and fried banana chips.
36. The light color with less browning, dehydrated food product produced by a method as claimed as claimed in claim 19 to 24, wherein the product is potatoes chips.
37. The light color with less browning, dehydrated food products as claimed in claim 36, wherein the dried and fried potato chips having acryl amide content reduced to 5 to 15 times, when compared with conventional fried potatoes chips.
38. The light color with less browning, dehydrated food products as claimed in claim 37, wherein the potatoes chips have 20 to 50 % reduced oil content after frying.
39. The light color with less browning dehydrated food product produced by a method as claimed as claimed in claim 25 to 29, wherein the product is beet root chips.
40. The light color with less browning dehydrated food product as claimed in claim 39, wherein the beet root chips having 2 to 3 time higher crispy texture and 0.8 to 1.0 times higher protein digestibility index, when compared with conventional dried beet root chips.
41. A closed hybrid dynamic dehydration system producing dehydrated food products having light color with less browning, when compared with conventional same food products, and having substantially same nutrional and vitamin values as that of natural food product, the said system comprises
a wet zone (2), wherein first heat-exchanger (4) in serpentine or coiled set of pipes are placed inside the wet zone (2), the said coiled pipes are operatively coupled with a fan (6a), which is collecting the hot air and passing the collected air over first heat-exchanger (4),
a dry zone (1), wherein second heat-exchanger (5) in serpentine or coiled set of pipes are placed inside the dry zone (1), the said coiled pipes are also operatively coupled with a fan (6b), which is collecting the cool air and passing over the heat-exchanger (5), a material zone (3), whereby the food is kept for drying, the said material zone is connecting the dry zone (1) and wet zone (3) of the said dehydration system, so as the hot air from dry zone passing over the food, drying the food by controlling the moisture and humidity level, and passing to the wet zone (2),

the said heat-exchangers (4 and 5) are carrying refrigerant liquid inside the pipes and connected by means of expansion device (20) and compressor (21)and the all said components are enclosed in a close chamber.
42. The closed hybrid dynamic dehydration system as claimed in claim 41, wherein the said material zone (3) is connecting the dry zone (1) and wet zone (2) of the said dehydration system by means of separation wall (7a & 7b), respectively. The said separation wall comprising converging holes so as to create sufficient pressure difference across the separation wall 7a & 7b and hot air from dry zone (1) passing over the food product, drying the food by controlling the moisture and humidity level, and passing to the wet zone (2)
43. The closed hybrid dynamic dehydration system as claimed in claim 41, wherein the wet zone comprising the temperature in the range of 10 Degree C to 70 Degree C, and relative humidity in the range of 5 to 80 % RH.
44. The closed hybrid dynamic dehydration system as claimed in claim 41, wherein the dry zone comprising the temperature in the range of 10 C to 60°C, and relative humidity in the range of 5 to 80 % RH
45. The closed hybrid dynamic dehydration system as claimed in claim 41, wherein the fan speed is controlled by controlling means, thereby controlling the rate of drying of the food.
46. The closed hybrid dynamic dehydration system as claimed in claim 41, wherein the said system optionally comprising one more heating means.
47. The closed hybrid dynamic dehydration system as claimed in claim 41, wherein a display panel is provided, whereby the details of parameters such as i.e. temperature, relative humidity, weight change during drying, moisture loss dehydration curve etc are displayed and a desired level of operational parameters is set out.
48. The closed hybrid dynamic dehydration system as claimed in claim 41, wherein the material zone is having platform horizontal or inclined or zig-zag shape or combination thereof on one or more load cells.

49. The closed hybrid dynamic dehydration system as claimed in claim 49, wherein the
said platforms/ tray are having perforations so that food product placed on them get
maximum exposure with air.
50. The closed hybrid dynamic dehydration system as claimed in claim 49, wherein the platforms / tray comprise contours, so that food products in the form of pieces do not fall down.
51. The closed hybrid dynamic dehydration system as claimed in claim 41, wherein the water drops collected in the wet zone is taken out by providing outlet in the wet zone, thereby reducing the moisture level in the circulated air inside the chamber.
52. The closed hybrid dynamic dehydration system as claimed in claim 41, wherein one
or more motorized valves are placed on the top of the said chamber in order to release
any excess pressure inside the chamber.
53. The closed hybrid dynamic dehydration system as claimed in claim 41, wherein
sensors are placed at various zones of the chamber, and coupled to the display panel.
54. The closed hybrid dynamic dehydration system as claimed in claim 41, wherein low
temperature drying is carried out approximately in the range of 10-60°C.
55. The closed hybrid dynamic dehydration system as claimed in claim 41, wherein the
said system is useful for preparing vegetable or fruit product such as apple chips,
banana chips, beet root chips and potato chips.
56. The closed hybrid dynamic dehydration system as claimed in claim 41, wherein the said system is capable to produce dried product having 5 to 15 times reduced acryl amide content.