FIELD OF THE INVENTION
The present invention relates to a process of paddy soaking in parboiling process.
In particular, the invention relates to a process of conservation of water requirement for paddy parboiling by adding a minimum extra quantity of water for subsequent batches of fresh paddy soaking in parboiling process in commercial scale. More particularly, the invention relates to treatment and reuse of excess soak water of previous batch for soaking subsequent batches of fresh paddy in soaking process, thereby conserving water and additional fuel requirements, making the process cost and energy efficient.
BACKGROUND OF THE INVENTION
The parboiling of paddy rice has its genesis principally in India. Paddy rice, or rough rice, is the term used in the art to describe rice as it is harvested which comprises the rice kernel, its surrounding bran layer and an outer husk. The process of parboiling is known more than 1000 years. There are mentions about parboiling in Tamil "Sankam" (Classical) literature dating back to 1000 years. Initially, parboiling involved simply soaking of paddy rice in room temperature water or warm water overnight and then drying in the sun, thereby aiding in rice being easily removed from the rice kernel. Today parboiling process is not just a separation process, instead parboiling process is carried out to enhance the nutrition value of rice, since amino acids, vitamins like thiamine etc. and other essential nutrients, normally present in the rice bran migrate to the rice endosperm during the water soaking and steaming, thus preserving the nutritional values originally contained in the bran. Parboiling is also beneficial, as the order by polyhedral structure of the compound starch granules are changed into a coherent mass due to gelatinization. With the starch in this state, the kernel is tougher and thereby provides a higher yield of whole rice kernels after milling.
A typical industrial par-boiling process involves soaking the paddy rice in hot water for few hours to
raise the water content of the paddy rice. Once the water content of the paddy rice has been raised to the desired level, the starch in the rice kernel is gelatinized, generally by steaming the soaked paddy rice at high temperature i.e more than 100° C. The product of the steaming step has high water content, therefore rice is steamed, without breaking the rice kernels. The steamed paddy rice is dried by use of ambient hot air. The partially dried rice is then hardened by leaving at room temperature for few tempering hours. During this time moisture water equilibrates within the kernel. Thereafter, the hardened paddy rice is dried to a desired moisture content by use of hot air. After the rice has been fully dried, it is dehusked in conventional manner to produce parboiled brown rice and further may be polished to remove the bran layer to produce parboiled white rice.
Many variations in process conditions and apparatus are known, however, they basically follow the same sequence of soaking, steaming and drying as described above.
The parboiling process produces a product which has many advantages over normal white rice. During parboiling, nutritionally valuable substances, such as vitamins and mineral salts, which are mainly found in the bran layers, migrate into the kernel, thus improving the nutritional value of the product after milling away the bran layer. Also the product of parboiling will be uniformly cooked to produce less sticky product.
The parboiling process has few disadvantages. The disadvantages are related to the necessity for introducing a large amount of water to the paddy rice to enable complete gelatinisation to take place. Since, a large amount of water is used in the soaking process, it necessitates the removal of a large amount of water during the drying stages. Generally, the paddy soaking process requires 120% - 130% water i.e 20%- 30% extra water in comparison to the weight of the paddy. During the soaking process only 20% -30% of the water is consumed by paddy, while remaining water is drained to an effluent treatment plant (ETP) for water treatment. Thus large amount of heated water is lost, making the process energy inefficient, as large amount of fuel consumption for heating water from normal temperature to elevated temperature is required. Moreover, the process also puts burden on the environment, since drained soak water contains impurities leachents and its lower pH increases chances of microbial activity.
Reference is made to US Patent No. 2,334,665 , wherein soak water during paddy treatment is re-used to insure optimum concentration of soluble products from the kernel hulls thus reducing loss of nutritive constituents to a minimum. However, soaking in this case is carried out in normal water or water heated upto only 37.7 °C, making process time consuming and having increased chances of microbial growth. Moreover, water is required to be filtered which is not cost effective process. This process does not imply the repeated use of the same excess soak water for more than one batch.
Reference is made to US patent No. 2525137, wherein excess water and steam condensate is pumped back through pipe to the head end of the tank for re-use during paddy treatment. However, the hot condensation water is collected then passed from heat exchanger for cooling to a between 82 to 93.3° C. Thus the cited process is not energy efficient and cost effective in terms of water conservation. This process also does not imply the repeated use of the same excess soak water for more than one batch.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a process which overcomes at least in part the disadvantages set out above, but which produces a product which is as good as or better than prior art parboiled rice, with energy conservation and total water requirement under commercial scale.
It is an object of the present invention to develop a process for the reuse of excess paddy soak waste water as such in nascent form without further processing or energy consumption in subsequent batches of in paddy parboiling.
Still yet another object of the present invention is to develop a process which saves fresh water consumption up to 80 % in parboiling process.
Yet another object of the present invention is to provide a process which reduces the necessity of heating large quantity of fresh water for soaking paddy.
Yet another object of the present invention is to provide a process which reduces fuel and electric power requirement of the process.
SUMMARY OF THE INVENTION
In the light of above objects, a process which reuses the excess hot paddy soak waste water for soaking paddy in parboiling is disclosed in the present invention. The invention relates to the treatment of used paddy soak waste water and its reuse in paddy soaking, thereby conserving fresh water and additional fuel requirement, making the process cost and energy efficient. The invention of the present invention greatly helps in reducing the fresh water requirement at soaking step. Almost 80% fresh water conservation is achieved in the soaking step.
Accordingly, in one aspect of the invention is disclosed a process for paddy soaking comprising the reuse of paddy soak used water as such without re-heating in parboiling process, wherein the soaking process comprises the steps of:
a) soaking pre-steamed paddy rice in excess hot water in a soaking tank to allow absorption of water;
b) transferring the hot unabsorbed paddy soak waste water as obtained in step a) as such from the soaking tank into a holding tank;
c) adding calcium hydroxide solution from an auto-doser into the holding tank to adjust pH;
d) allowing heavy impurities to settle on its own in the holding tank to obtain clear supernetant water;
e) transferring the clear supernetant water as obtained in step d) from the holding tank into the soaking tank ;
f) adding fresh hot water from fresh water tank into the soaking tank to compensate for the water as absorbed in step a);
g) soaking fresh batch of paddy into the soaking tank ;and
h) repeating the process steps b-g for soaking paddy.
In an embodiment of the invention is provided a process, wherein the excess hot water in the soaking
tank , as used in step a) is in the range of 120 9c to 130% of the weight of paddy soaked.
In further embodiment of the invention is provided a process, wherein the paddy rice is soaked in the soaking tank as in step a) for a period in the range of 4 to 6 hours at a temperature in the range of 60 -
70 °C.
In another embodiment of the invention is provided a process, wherein the amount of water absorbed in step a) is in the range of 20 % to 30% of the weight of paddy soaked.
In another embodiment of the invention is provided a process wherein the unabsorbed hot paddy soak waste water as obtained in step a) has amino acids, vitamins and minerals leached from the paddy rice.
In an embodiment of the invention is provided a process, wherein the holding tank is a steel tank.
In yet another embodiment of the invention is provided a process, wherein the holding tank is an insulated tank.
In still another embodiment of the invention is provided a process, wherein temperature of the insulated holding tank is maintained at a temperature in the range of 60-70°C, to ensure that no undesired microbial growth occurs.
In further another embodiment of the invention is provided a process, wherein the calcium hydroxide solution from the auto-doser is added in controlled manner into the holding tank as in step c) to neutralize the pH of the used paddy soak waste water.
In another embodiment of the invention is provided a process, wherein the auto-doser is a apparatus having valves which control the flow of calcium hydroxide solution into the holding tank.
In still another embodiment of the invention is provided a process, wherein the calcium hydroxide solution adjusts the pH in the holding tank in the range of 6.5 to 7.5.
In an embodiment of the invention is provided a process, wherein the heavy impurities are allowed to settle at its own in the holding tank as in step d) for a period in the range of 2 to 3 hours to obtain clear supernetant hot water.
In another embodiment of the invention is provided a process, wherein the amount of fresh hot water added from the fresh water tank into the soaking tank to compensate for water consumed at step a) is in the range of 20% to 30% of the weight of paddy rice soaked.
In an embodiment of the invention is provided a process, wherein temperature of the hot water added into the soaking tank is in the range of 60-70° C.
In an embodiment of the invention is provided a process, wherein the process is repeated six times.
In another aspect of the invention is provided an apparatus for paddy processing in parboiling process wherein the apparatus comprises a paddy storage bin , pre-steaming tank , soaking tank, holding tank , fresh water tank , an auto-doser containing calcium hydroxide solution and an ETP plant.
The present invention achieves the objects of reducing water consumption during parboiling process by reusing paddy soaked waste water and also reduces fuel and electric power requirement. The present invention achieves the said object in a simple and cost effective manner as will be evident from the description of the invention that follows herein after.
These aspects together with other aspects of the present invention , along with the various features of novelty that characterize the present invention, are pointed out with particularity in the claims annexed hereto and forms part of this invention. For a better understanding of the present invention, its operating advantages, and the specific objects attained by its uses, references should be made to accompanying drawing and the descriptive manner in which there is illustrated an exemplary embodiment of the present invention.
STATEMENT OF THE INVENTION
According to the present invention, there is provided a paddy soaking process comprising the reuse of paddy soak used waste water in parboiling process, wherein the soaking process comprises the steps of soaking the pre-steamed paddy rice in excess hot water in a soaking tank to allow absorption of water followed by transfer of the unabsorbed paddy soak waste water from the soaking tank into a holding tank and adding calcium hydroxide solution from the auto-doser into the holding tank. The paddy soak waste water is allowed to stand in a holding tank , so that heavy impurities settle in the holding tank to obtain clear supernetant hot water. The clear supernetant hot water obtained is transferred from the holding tank into the soaking tank. Further fresh hot water from fresh water tank is added into the holding tank to compensate for the water absorbed and fresh batch of pre-steamed paddy rice paddy rice is soaked into the soaking tank .This process is repeated upto six times.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Fig 1 illustrates the diagram of an apparatus used for paddy processing in parboiling process wherein used soaked waste water is reused for soaking paddy.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING DRAWING
The term 'paddy' and 'paddy rice' herein used are interchangeable . Similarly, 'used water', 'soak water', 'paddy soak water', 'paddy soak waste water' herein used are interchangeable.
The exemplary embodiment described herein detail for illustrative purposes are subject to many variations in steps and structure. It should be emphasized, however, that the present invention is not limited to a particular process for soaking paddy rice in parboiling as shown and described.
The accompanying Fig 1 shows an apparatus for paddy processing in parboiling process. The apparatus
comprises storage bin (1) wherein the paddy rice is stored. Prior to storing the paddy rice in the storage bin (1), the paddy rice is initially subjected to preliminary cleaning process to remove undesired components. Further from the storage bin (1) the paddy rice is allowed into a pre- steaming tank (2) for 1-2 minutes (4 to 6 kg/cm2 line pressure) to obtain pre-steamed paddy rice. This pre-steaming ensures that the entrapped air in the rice germ is removed, thereby allowing efficient absorption of hot water upon further soaking. The pre-steamed paddy rice is allowed to soak into a soaking tank (3).
The pre-steamed paddy is kept in the soaking tank (3), so that sufficient water is absorbed by the paddy rice. Soaking is carried out in excess hot water, since desired soaking is achieved in few hours whereas cold water requires 24 hours to three days for soaking and spoils the product with foul smell of fermentation.
The amount of soaking water required is to be sufficient to effect an increase in the water content of the paddy rice. The minimum amount of water needed is the amount which is equal to the water lost to evaporation during the soaking period and the amount of water absorbed by the paddy rice. Generally, the paddy soaking process requires 120- 130% water i.e 20-30% extra water in comparison to the weight of the paddy e.g for 1000 kg of paddy 1200 -1300 liters of water is utilized. During the soaking process, water absorbed is 20 to 30 % of the weight of the paddy soaked.
In the soaking step, the soaking time is dependent upon the soaking temperature, the higher the soaking temperature, the lower the time needed to achieve the desired water content in the paddy rice. The table below indicates the inverse temperature and soaking time relationship.
(Table Removed)
It has been found that with the process of this invention, desired soaking can be achieved with a soaking temperature ranging from 60°C to 70°C with soaking time in the range of 4-6 hours.
During the paddy soaking step water is heated and hot water obtained is used for soaking the paddy rice. However, only 20% to 30 % of hot water is absorbed during the soaking process. Generally in the known parboiling processes, the rest of the unabsorbed hot water is drained into effluent treatment plants for water treatment and purification. However, in the present case, there is no need for draining the excess hot water. Instead the hot paddy soak waste water is treated in situ and reused, thereby reducing energy requirements. Thus present process obviates the necessity of repeated heating of the water to elevated temperatures.
The remaining used paddy soak waste water from the soaking tank (3) is transferred into a holding tank (4) and is treated to be reused for soaking fresh batch of paddy rice. The treatment of used soak water involves storage of the used paddy soak waste water in the holding tank (4). The holding tank (4) is an insulated steel tank. In the insulated steel tank, temperature is maintained in the range of 60 -70°C. The holding tank (4) has approximate capacity of 50,000 liters. In the cold soak water, there is chance of growth of microbes like staphylococci, lactic acid bacteria and yeasts. To avoid this nuisance, the holding tank (4) is insulated to maintain a high temperature in the range of 60 -70°C .
The paddy soak waste water is stored in the holding tank (4) for a time period in the range of 2 to 3 hours to allow the impurities to settle at its own at the bottom of the holding tank (4).
The pH value of the hot paddy soak waste water stored in the holding tank (4) is slightly acidic. To neutralize the acidic pH of the water, solution of calcium hydroxide contained in an auto-doser (5) is added into the holding tank (4) .The addition of calcium hydroxide from the auto-doser (5) is controlled by valves, so that the addition of calcium hydroxide into the holding tank (4) adjusts the pH of the used paddy soak waste water. The pH in the holding tank (4) is adjusted in the range of 6.5 to 7.5. The amount of the calcium hydroxide added depends on the acidity of the paddy soak waste water.
Once the heavy impurities are settled down in the holding tank (4), the clear supernetant hot water is obtained and the clear supernetant hot water is transferred from the holding tank (4) in to the soaking tank (3).
During the paddy soaking process, the amount of water used by paddy rice is in the range of 20 % to 30 %. For soaking fresh batch of paddy in the reused soak water, 20 % to 30 % of the fresh water is added from fresh water tank (6) into the soaking tank to compensate for the water absorbed during the soaking process. The temperature of the water in the fresh water tank (6) is in the range of 60 to 70°C. The addition of water achieves the desired equilibration of the water content of the paddy rice. The soaking step occurs within the same temperature and time parameters mentioned above, however, the soaking step is modified by reusing the treated paddy soak waste water.
During the soaking process, many components are leached out into the unabsorbed waste water surrounding the paddy. The reused waste water act as excellent source of many nutrients like high amount of amino acids and vitamins like niacin, thiamine. It also contains minerals like magnesium, iron and zinc. The water containing the nutrients is reused for soaking fresh batch of paddy. The soaking of paddy in this enriched water helps in better absorption of the nutrients and the product obtained by this process exhibits high nutrition content.
The paddy soak waste water is used upto 6 times for soaking fresh batches of paddy and thereafter waste water is drained into an effluent treatment plant (7).
The soaked paddy is further allowed into a post steaming tank for further processing.
The reuse of soak waste water has lot of economic significance. It drastically reduces the water requirement by almost 80 % , thereby conserving the water. It also reduces the necessity of heating large quantity of water repeatedly, thus saving fuel and energy by almost 80%. The process of the present invention reduces fuel and electric power requirement for running the boilers, water pumps etc. The power consumption for running the ETP (7) is also reduced. The process is also eco- friendly, as it reduces emissions from fuel burning and also the effluent which is discharged finally is loaded with
less impurities, thus reducing the load on natural resources.
It can thus be seen that the present invention provides an advantageous process .The product obtained is free of impurities leachants, and there is no color formation. The novel and inventive process maintains normal pH of the water and does not allow any microbial growth. Thus present process is improved, efficient and economic in comparison to known processes.
EXAMPLE 1
25,000 kilograms of the pre-steamed paddy rice from the pre-steaming tank is soaked in the soaking tank containing 30,000 liters of the hot water having temperature 60 °C for 6 hours to allow absorption of water. During this period the paddy rice absorbs 5000-7500 liters of water. The remaining excess hot water is transferred into an insulated holding tank having temperature maintained at 60°C. The calcium hydroxide solution from the auto-doser is added into the holding tank till the pH achieved is 6.5 to 7.5. The water is allowed to stand in the holding tank for 2 hours, so that heavy impurities are settled at the bottom of the holding tank to obtain the clear supernetant hot water. The clear supernetant obtained is transferred into the soaking tank and fresh 6000-8000 liters of fresh hot water from the fresh water tank having temperature 60°C is added into the soaking tank. A fresh batch of paddy is added into the soaking tank containing used soak waste water.
EXAMPLE 2
32,000 kilograms of the pre-steamed paddy rice from the pre-steaming tank is soaked in the soaking tank containing 38,400 liters of hot water having temperature 70°C for 4 hours to allow absorption of water. During this period paddy rice absorbs 6,400-9,600 liters of water. The remaining hot water is transferred into an insulated holding tank having temperature maintained at 70°C. The calcium hydroxide solution from the auto-doser is added into the holding tank till the pH achieved is 6.5 to 7.5.The water is allowed to stand in the holding tank for 3 hours, so that heavy impurities are settled at the bottom of the holding tank to obtain the clear supernetant hot water. The clear supernetant hot water obtained is transferred into the soaking tank and fresh 7,000-10,000 liters of hot water from the fresh water tank having temperature 70°C is added into the soaking tank. A fresh batch of paddy rice is added
into the soaking tank containing used soak waste water.
The foregoing description of the specific embodiment of the present invention have been presented for purpose of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise form disclosed, and obviously many modifications and variations are possible in the light of above mentioned teachings. The embodiment were chosen and described in order to best explain the principles of the present invention and its practical application,and to thereby enable others skilled in the art to best utilize the present invention and various embodiment with various modifications as are suited to the particular use contemplated . It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.

We Claim:
1. A paddy soaking process comprising the reuse of paddy soak used waste water in parboiling
process, wherein the soaking process comprises the steps of:
a) soaking pre-steamed paddy rice in excess hot water in a soaking tank to allow absorption of water;
b) transferring unabsorbed hot paddy soak waste water as obtained in step a) from the soaking tank into a holding tank ;
c) adding calcium hydroxide solution from an auto-doser into the holding tank to adjust pH;
d) allowing heavy impurities to settle in the holding tank to obtain clear supernetant hot water;
e) transferring the clear supernetant hot water as obtained in step d) from the holding tank into the soaking tank;
f) adding hot water from fresh water tank into the soaking tank to compensate for the water as absorbed in step a);
g) soaking fresh batch of pre-steamed paddy rice into the soaking tank ; and
h) repeating the process steps b-g for soaking paddy.
2. The process as claimed in claim 1, wherein excess hot water used in step a) is in the range of 120% to 130% of the weight of paddy rice soaked.
3. The process as claimed in claim 1, wherein paddy rice is soaked in the soaking tank as in step a) for a period in the range of 4 to 6 hours at a temperature in the range of 60 -70 °C.
4. The process as claimed in claim 1, wherein the amount of water absorbed in step a) is in the
range of 20 % to 30 % of the weight of paddy rice soaked.
5. The process as claimed in claim 1, wherein the unabsorbed hot paddy soak waste water as
obtained in step a) has amino acids, vitamins and minerals leached from the paddy rice.
6. The process as claimed in claim 1, wherein the holding tank is a steel tank.
7. The process as claimed in claims 1 or 6, wherein the holding tank is an insulated tank.
8. The process as claimed in claim 6, wherein temperature of the insulated holding tank is
maintained at a temperature in the range of 60°C to 70 °C, to ensure that no undesired microbial growth
occurs.
9. The process as claimed in claim 1, wherein the calcium hydroxide solution is added into the
holding tank from the auto-doser as in step c), adjusting the pH in the holding tank in the range of 6.5
to 7.5.
10. The process as claimed in claim 1, wherein the heavy impurities are allowed to settle in the
holding tank as in step d) for a period in the range of 2 to 3 hours to obtain clear supernetant hot water.
11. The process as claimed in claim 1, wherein the amount of fresh hot water added from the fresh water tank into the soaking tank as in step f) , to compensate for consumed water, is in the range of 20% to 30% of the weight of paddy soaked.
12. The process as claimed in claims 1 or 11, wherein temperature of the fresh hot water added in the soaking tank is in the range of 60 to 70° C.
13. Use of the process as claimed in any of the proceeding claims to produce parboiled rice.
14. A paddy soaking process for the reuse of paddy soak used waste water in parboiling process as
herein described with reference to the examples disclosed in the description and the accompanying
drawing.