Claims:1. A semi continuous steam sterilizer for sterilization and cooling of product comprises of sterilization vessel and cooling vessel, wherein both vessels comprises of stirrer at their bottom portion for shuffling of product which rotate either continuously or intermittently.
2. A semi continuous steam sterilizer as claimed in claim 1, wherein stirrer comprises of an assembly of horizontal shaft, semi circular arc shaped frame, boss and integrally connected arm and scraping blades in which shaft is rotated at horizontal axis.
3. A semi continuous steam sterilizer as claimed in claim 1, wherein outer side of sterilization vessel and cooling vessel is insulated to reduce loss of heat.
4. A semi continuous steam sterilizer as claimed in claim 1, comprises of one way valves for transfer of material form hopper to sterilizing vessel, sterilizing vessel to cooling vessel and from cooling vessel to hopper.
5. A semi continuous steam sterilizer as claimed in claim 1, wherein product is transferred from sterilization vessel to cooling vessel by pressure difference and gravitational force which is created by maintaining sterilization vessel above atmospheric pressure and maintaining cooling vessel below atmospheric pressure.
6. A semi continuous steam sterilizer as claimed in claim 1, compact in size and requires low ground space and oriented in vertical, horizontal, inclined or any other suitable orientation.
7. A method of sterilization in semi continuous steam sterilizer comprises of sterilization and drying in sterilization vessel and cooling and drying in cooling vessel.
8. A method of sterilization and drying in sterilization vessel in semi continuous steam sterilizer as claimed in claim 7, comprises of following events:
a) Preheating of product, wherein preheating is defined as preheating the interior of the container system by circulating steam into the jacket for sufficient time to raise the temperature of the interior of the container system substantially to a temperature at which the sterilizing steam is injected into the interior of the closed sterilization vessel.
b) Preconditioning of product, wherein preconditioning is defined as opening of the pores of product by steam and vacuum cycle, wherein cycle of steam and vacuum is as following:
i) Lowering the pressure in the container system below atmospheric pressure for preconditioning,
ii) Injecting sterilizing steam into the container system to achieve pre assigned % of sterilization temperature or pressure.
c) Sterilization of product, wherein sterilization is defined as sterilizing the product by pulsation which includes cycle of moisture addition and moisture removal by injecting steam and evacuating sterilization vessel respectively.
d) Drying of product, wherein drying is defined as cycle of moisture addition and moisture removal by injecting steam and evacuating sterilization vessel respectively.
9. A method of cooling and drying in cooling vessel in semi continuous steam sterilizer as claimed in claim 7, comprises of cooling and partial drying under vacuum which includes moisture addition and moisture removal by injecting steam and evacuating cooling vessel respectively.
10. A method of preconditioning as claimed in claim 8, wherein preconditioning process comprises of n number of steam and vacuum cycles.
, Description:Field of the Invention
The present invention relates to the field of sterilization. In particular, the present invention relates to a semi continuous steam sterilizer and method of sterilization for dry powder, spices or herbs in powder form, flake or whole material to render them suitable for human consumption and to maintain the safety of food.
Background of the Invention
The steam sterilization treatment does not use chemicals hence no chemical residual effect will be found in the treated products and therefore, it is not harmful to the health.
At present, two types of steam sterilizers are available:
(1) Batch sterilizer
(2) Continuous sterilizer.
In continuous steam sterilizer, product is continuously fed in sterilizer and came out from sterilizer, while in batch type sterilizer process is intermittent as product is loaded, sterilized then unloaded.
Continuous steam sterilizer is large in size and acquire large ground space due to separate parts of machinery like feeding system, sterilizer, continuous fluid bed dryer cum cooler, air blowing system, air heating system, cyclone etc.
Batch type sterilizer is also large in size and requires sterile room, non sterile room and trolley for loading materials. Shuffling of stagnant material is not uniform in batch type sterilizer, so uniform sterilization of stagnant material is not achieved.
In these types of sterilizer, rotating element (mostly shaft or screw) in form of cylindrical or conical or other suitable shape is mounted vertically or axially. This rotating element is not capable of segregate material from machine and causes loss of product in more or less proportion. Product or material far away from rotating element cannot be shuffled at proper temperature for proper time, which causes problem in proper agitation of product. All these parameters affect physical properties of product like volatility of oil, moisture content of product, taste & colour of product etc. These problems are overcome by the present invention.
US2303021 disclosed method for preserving perishable food. The apparatus is consisting of metal pressure kettle A, a cooling kettle B and a dry heat sterilizer C. The pressure kettle A is provided with a cover A1 and a plunger A2 for pushing foods which have been sterilized into the cooling kettle B. Kettle A is provided with a jacket A3 through which superheated steam can be circulated by means of pipes A4 and A5. Kettle A and kettle B do not have insulating layer which causes loss of steam and chilled water in kettle A and kettle B respectively because these kettles are directly exposed to atmosphere. Valve B2 and B7 are operated manually. There is no arrangement for pre conditioning and pre heating of product and hence there is no scope for vacuum pump and steam line in said kettle A along with steam circulating jacket A3. Kettle B does not have any stirrer.
US2303021 is limited to non acid foods. Though US2303021 mentioned about replacing plunger by stirrer but it could not serve the purpose of stirrer because of its shape, size and design and also there is lack of hopper, load measuring instrument, insulation, digital controls, vacuum line, direct heating steam line and stirrer.
To overcome above mentioned problems, the present invention provides a semi continuous sterilizer with a hopper, load measuring instrument, heating stream, vacuum line, insulation, stirrer and digital controls in which product is easily preheated, preconditioned, sterilized and dried.
Objects of the Invention
The main object of present invention is to provide a semi continuous sterilizer which comprises of sterilization vessel and cooling vessel, wherein sterilization vessel product is preheated, preconditioned, sterilized and dried as well as continuously shuffled by horizontally oriented stirrer at the lower portion of vessel wherein said shuffling is essential to reduce loss of volatile oils, to prevent change of colour and to reduce excessive loss of moisture in dry herbs or spices.
Another object of present invention is to provide a semi continuous sterilizer which comprises of sterilization vessel and cooling vessel, wherein cooling vessel product is cooled and dried under vacuum as well as continuously shuffled by horizontally oriented stirrer at the lower portion of vessel.
Another object of present invention is to provide an insulating medium to sterilization vessel and cooling vessel of semi continuous sterilizer to reduce loss of heat.
Another object of present invention is to provide a vacuum means for preconditioning of product in semi continuous sterilizer.
Another object of present invention is to provide a sterilizer for automatic processing of food materials which requires less ground space and compact in size.
It is yet another object of present invention to provide the method of sterilization and drying in sterilization vessel and cooling and drying in cooling vessel.
Summary of the Invention
The main object of present invention relates to provide a semi continuous steam sterilizer and a process for sterilizing dry powder, spices or herbs in powder form, flake or whole material to render them suitable for human consumption. The sterilizer apparatus of present invention comprises of sterilization vessel and cooling vessel wherein said both vessels have horizontal stirrer at lower portion of vessel for shuffling of material as it rotates about horizontal axis. Sterilization process and cooling process occurring in semi continuous sterilizer are simultaneous as both vessels are independent from each other. The transfer of product from sterilization vessel to cooling vessel requires pressure difference and gravitational force.
The one way valves of present invention are located at top and bottom portion of the outer side of sterilization vessel and at bottom of cooling vessel. These valves are responsible of transfer of materials.
The horizontal stirrer in sterilization vessel and cooling vessel of present invention is responsible for continues shuffling of material. The assembly of stirrer is consist of horizontal shaft, boss and integrally connected arm and scraping blades which helps in preventing loss of material adhered to vessels.
The process of present invention requires less time for loaded product to get unloaded. The process time mainly depends on product, micro load and initial temperature, although sterilization and cooling process of present invention ends with in 30 minute.
The method of sterilization in semi continuous steam sterilizer of present invention includes preheating, preconditioning, sterilization and drying of product in sterilization vessel and cooling and drying of product in cooling vessel.

Drawings
FIG.1 shows diagrammatic view of semi continuous vertically oriented dry powder processing machine with sterilization vessel and cooling vessel.
FIG.2 shows diagrammatic top view of semi continuous vertically oriented dry powder processing machine with pneumatic conveying system and top view of said vertical machine.
FIG.3 shows diagrammatic view of stirrer assembly along with steam line, vacuum line (pump), and hepa filter.

Detail description of the Invention
In general, sterilization refers to any process that removes or kills all forms of life and other biological agent including transmissible agents which are present in a specified region, such as a surface, a volume of fluid, medication, or in a compound such as biological culture media.
Sterilization is achieved by different methods such as heat, chemicals, irradiation, high pressure, and filtration.
Heat sterilization includes different method such as steam, dry heat, flaming, incineration, tyndallization and glass bead sterilization.
Chemical sterilization is achieved by different chemical agents such as ethylene oxide, nitrogen oxide, ozone, glutaraldehyde and formaldehyde, hydrogen peroxide and peracetic acid.
Radiation sterilization is achieved by non-ionizing radiation sterilization and ionizing radiation sterilization methods.
Sterile filtration is used for fluids that would be damaged by heat, irradiation or chemical sterilization such as drug products which can be sterilized by microfiltration using membrane filters.
Food products are mainly sterilized by heat sterilization as it does not involve any chemical treatment or radiation.
Exposure of microorganism to steam under pressure achieves their destruction by the irreversible denaturation of enzymes and structural proteins. To achieve this goal present invention provides semi continuous steam sterilizer for dry powder, spices or herbs in powder form, flake or whole material.
Embodiment of present invention includes a method for sterilizing dry powder, spices or herbs in powder form, flake or whole material to render them suitable for human consumption.
The semi continuous steam sterilizer apparatus of present invention mainly comprising of two parts:
1) Sterilization vessel
2) Cooling vessel
Sterilizing vessel and cooling vessel are provided with horizontal shaft and stirrer assembly at lower portion of vessel for shuffling of the products.
Sterilization temperature used in present invention for sterilization of dry powder, spices or herbs in powder form, flake or whole material is in the range of 70 to 80 ºC.
The application time and temperature for sterilization depends on the following factors:
• Presence of microorganisms
• Properties of the food product
• Initial temperature the products
• pH of the product
• Microbial count
FIG. 1 shows design of semi continuous steam sterilizer with Sterilization vessel A and cooling vessel B. Both vessels are similar in construction.
Sterilization vessel is first upper part of semi continuous sterilizer where process starts. The sterilization vessel is enclosed container shaped vessel with a cylindrical shaped middle portion and hemispherical shaped bottom.
Sterilization vessel has hopper 1 at its top part for loading of material. Hopper is fitted with load cell 2 which measures input load of the product. One way valve 3 is located in between hopper 1 and sterilization vessel ‘A’ which allows product to drop only in downward direction.
Steam line 4, vacuum line (pump) 5 and hepa filter 6 are located at top portion of sterilization vessel as shown in fig. 1in top view. The steam in line 4 is provided for injection of steam in sterilization vessel which is responsible for pre conditioning and sterilization of product, while vacuum line 5 creates vacuum inside sterilization vessel to remove most air and gases from sterilization vessel ‘A’. The vacuum line 5 is also utilized for drying and partial cooling by removing moisture content. The hepa filter 6 serves the purpose of injecting bacteria free air from atmosphere to sterilization vessel and wherein said bacteria free air increases pressure inside sterilization vessel ‘A’. Sterilization vessel consists of three layers of stainless steel which are inside layer 9, middle layer 8 and outer layer 7. A space between inner layer and middle layer is called jacket 10, while a space between middle layer and outer layer is for insulation 11. In jacket 10, steam is passed which prevents condensation in sterilization vessel ‘A’. In insulation space 11 insulating material is inserted for the purpose of insulation. Sterilization vessel has manhole 12 for manual inspection.

Sterilization vessel has horizontal shaft and stirrer (shown in FIG.3) at its bottom portion wherein stirrer comprises of semi circular arc shaped frame 13, shaft, boss section with integrally connected arm and blades. The main function of stirrer is to shuffle each and every particles of product at set temperature for appropriate time. Semi circular arc shaped frame 13 is connected with another semi circular arc shaped frame at horizontal shaft 14A. The horizontal shaft 14A is connected with boss and arm. The scraping blades are located on the circumference of semi circular arc shaped frame 13. The horizontal shaft 14A of stirrer is attached with gear box 15A of motor. Legs 16A are welded to sterilization vessel and act as support to sterilization vessel. The whole structure of sterilization vessel is supported by mild steel structure 30.
The one way valve 18 at bottom portion of sterilization vessel is used for loading the product from sterilization vessel ‘A’ to cooling vessel ‘B’. Sterilization vessel also has steam line 17 at its bottom portion for supplying steam in vessel ‘A’ which serves the purpose of sterilization of the product. For preheating, one steam line is diverted towards jacket 10 from steam line 4 (not shown in figure).
The description of above said sterilization vessel is only for example. The sterilization vessel is not limited to this description. The terms and expressions used in description of sterilization vessel are employed only for description but are not limited because modifications are there for achieving same purpose in different ways which are known to world. There is neither any limitation in achieving same purpose by other best suitable method nor sterilization vessel is limited to above description in any way.
Referring FIG. 1, construction and working of cooling vessel is described as following:
The function of cooling vessel is to cool the sterilized product. Similar to sterilization vessel ‘A’, cooling vessel ‘B’ also has vacuum pump 31, hepa filter 32, one way valve at top and bottom portion, horizontal stirrer (coupled with motor gear box 15B), legs 16B for support, manhole 34 for inspection etc.
The main difference between cooling vessel ‘B’ and sterilization vessel ‘A’ is that in cooling vessel only lower half of the vessel is utilized for cooling purpose. The lower half of cooler has three layers 19, 20 and 21 of stainless steel while upper half of cooler has only single layer 19 of stainless steel. In lower half of cooler, chilled water is circulated though Jacket 22 which is located between inner layer 19 and middle layer 20, while insulation space 23 is between middle layer 20 and outer layer 21 where insulating material is inserted.
Cooling vessel has hopper 25 at its below portion for collection of processed product from cooler ‘B’. The processed product might be collected in jumbo bag or large container. This hopper 25 is also provided with load cell 26 for measurement of output load. As the machine is operated by PLC based controller, required data is stored in computer for further analysis in future.
From input and output load data one can analyze amount of product remained inside the machine and take necessary steps to reduce loss of material. Cooling vessel is also supported by mild steel structure 30.
The description of above said cooling vessel B is only for example. The cooling vessel B is not limited to this description. The terms and expressions used in description of cooling vessel are employed only for description but are not limited to disclose invention because modifications are there for achieving same purpose in different ways which are known to world. There is neither any limitation in achieving same purpose by other best suitable method nor cooling vessel is limited to above description in any way.
The semi continuous steam sterilizer apparatus is compact in size and requires low ground space as compared to batch steam sterilizer and continuous steam sterilizer. Steam sterilizer of present invention with a unique design of horizontal stirrer is responsible for continoues shuffling of input material at set temperature for enough time.
The orientation of sterilizer can be vertical, horizontal, inclined or any other suitable orientation depending on space available and capacity of machine, preferably in vertical orientation.
Process flow
The events occurring during sterilization in the semi continuous sterilizer is as following:
1. Loading of product in hopper through hoist chain, crane, pneumatic conveyor, jumbo bag etc.
2. Measurement of loaded product by load cell 2 and storage of data in computer for future purpose.
3. Opening of valve 3 and transfer of product from hopper to sterilization vessel ‘A’.
4. Closing of valve 3 and heating of sterilization vessel to a suitable temperature (depending on product, micro load and initial temperature of product) by circulating steam in jacket 10 of sterilization vessel ‘A’, this process is called preheating.
5. After pre heating, product is pre conditioned and sterilized.
A cycle of pre conditioning and sterilization is described below:
a) Lowering the pressure in the sterilization vessel below atmospheric pressure for pre conditioning,
b) Injecting sterilizing steam into the sterilization vessel to achieve pre assigned % of sterilization temperature or pressure,
c) Lowering the pressure in the sterilization vessel below atmospheric pressure for pre conditioning,
d) Injecting sterilizing steam into the sterilization vessel to achieve assigned % of sterilization temperature or pressure,
e) Lowering the pressure in the sterilization vessel below atmospheric pressure for pre conditioning,
f) Injecting sterilizing steam into the sterilization vessel to reduce the bacteria present in or on the product to an acceptable level,
g) Lowering the pressure in the sterilization vessel below atmospheric while drying and cooling the product in the container system by maintaining container system in a closed condition isolated from the external atmosphere,
h) Elevating the pressure in the sterilization vessel by introducing a substantially bacteria-free air through Hepa filter and then evacuating the contents of the sterilization vessel.
6. Breaking of vacuum causes ending of process in sterilization vessel.
7. Opening of valve 18 and transfer of product/material from sterilization vessel to cooling vessel by gravity difference and/or pressure difference.
8. Closing of valve 18.
9. After closing of valve 18, next batch of product is loaded in sterilization vessel and above mentioned process is repeated.
10. Loading product in cooling vessel ‘B’ and cooling of product by circulating chilled water in jacket 22 of cooling vessel.
11. Partial drying of product under vacuum for set time period with continuously shuffling of product for set time and temperature.
12. Drying and cooling of product.
13. Breaking of vacuum, by inserting bacteria free clean air through hepa filter 32 and atmospheric pressure is achieved.
14. Unloading of product from cooling vessel ‘B’ to hopper 25 by opening of valve 24.
15. Closing of valve 24.
After closing of valve 24, next batch of sterilized product is transferred to cooler ‘B’.
In sterilization vessel, product is sterilized above atmospheric pressure and continuously shuffled during whole process by horizontal stirrer for set time and temperature wherein set time and temperature depend on product, micro load and initial temperature of product.
The invention is disclosed here completely in best possible way with 2 drawings. There is neither any limitation in achieving same purpose by other best suitable method nor invented machine is limited to above description in any way. Words such as spices or herbs or foods are employed only for illustration by example but not limited to this particular case. Same invented machine can be utilized at other best suitable place such as in pharmaceutical industries.