Microwave or hydrogen peroxide-microwave combined sterilization method of potato whole powder

Abstract

The invention belongs to the field of food, and particularly relates to a sterilization method of starch raw materials such as potato whole powder. The invention provides a sterilization method of potato whole powder, which comprises the following schemes: a scheme I, carrying out microwave sterilization on moderately polluted potato whole powder, and a scheme II, carrying out hydrogen peroxide-microwave combined sterilization on severely polluted potato whole powder. On the premise that the sensory characteristics and the processing characteristics of the potato powder are not influenced basically, the total number of bacterial colonies of the whole potato powder can be reduced to 1.0 * 10 < 4 > CFU / g or below through a proper sterilization treatment mode. The potato whole powder before and after treatment has no obvious sensory difference, and the color, aroma, taste, shape and other indexes of the finished potato chips are not influenced.

Description

Technical Field

[0001] The invention belongs to the field of food, and in particular relates to a method for sterilizing starch raw materials such as whole potato flour. Background Art

[0002] Potato flour is a fine granular, flake or powder product made from fresh potatoes through processes such as washing, peeling, selecting, slicing, rinsing, pre-cooking, cooling, steaming, mashing, dehydrating and drying. Potato flour has a wide range of uses in the food industry. With potato flour as the main raw material, scientific formula and corresponding nutritional ingredients can be used to make complete nutrition, multi-variety and multi-flavor convenience foods, such as snowflake breakfast porridge, meat rolls, biscuits, milk potato flour, meat patties, meatballs, dumplings, crispy magic slices, etc.; with potato flour as an "additive", cold drinks, convenience foods, puffed foods and a variety of nutritious foods and snack foods for special groups (hyperlipidemia, diabetes, the elderly, women, children, etc.) can be made.

[0003] Potatoes are one of the main food crops. Due to their strong seasonality, easy rot, and the huge space and energy consumption required for fresh storage, harvested potatoes are generally processed into potato flour as soon as possible to reduce storage difficulties. During the production process of potato flour, it is easily contaminated by environmental microorganisms. According to the results of random inspections, the total number of colonies in potato flour on the market can be as high as 1.0×10 6 CFU / g and above.

[0004] After culture and microscopic examination, the microorganisms in potato flour were mainly bacilli; after enrichment culture and 16S sequencing, it was proved that more than 60% of the microorganisms in the powder were Bacillus subtilis. Bacillus subtilis is one of the main contaminants of flour food raw materials. It can produce spores with strong resistance at high temperature. When the conditions are suitable, it will germinate and grow again and is difficult to kill. Bacillus subtilis contamination poses a huge threat to food safety. When potato chips are produced with contaminated potato whole flour as raw material, the total number of colonies in the product is still 1.0×10 5 CFU / g or above, which poses a great threat to food safety.

[0005] The patent of CN218187325U provides a potato starch vacuum sterilization device, including a processing box, a plurality of heating plates and an exhaust pipe, wherein the plurality of heating plates are fixed at intervals on the outer wall of the processing box, the exhaust pipe is connected and installed on the processing box and is externally connected to a vacuum pumping mechanism, and also includes a movable mechanism, which is rotatably installed on the processing box, and the movable mechanism is used to move the potato starch in the processing box. The utility model rotates the servo motor to rotate the rotating rod, thereby driving the rotating plate to rotate so that the potato starch remains active during vacuum sterilization, thereby achieving the effect of comprehensive sterilization of the potato starch, and the chain sprocket drives the threaded rod to rotate, thereby causing the ring plate to move up and down, driving the upper inclined block and the lower inclined block to move up and down, thereby achieving the effect of scraping the potato starch on the inner wall of the processing box. However, the patent cannot achieve effective sterilization of potato whole powder. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for sterilizing whole potato flour with good sterilization effect.

[0007] In order to solve the above technical problems, the present invention provides a method for sterilizing whole potato flour, comprising the following schemes:

[0008] Solution 1: Use microwave sterilization for moderately contaminated potato flour:

[0009] Option 2: For severely contaminated potato flour, use hydrogen peroxide-microwave combined sterilization.

[0010] As an improvement of the sterilization method of potato whole flour of the present invention:

[0011] Solution 1: Use microwave sterilization for moderately contaminated potato flour:

[0012] The microwave intensity is 0.75-1.45kW / kg, and the microwave sterilization time is 3.5-5.0min;

[0013] 0.1×10 5 CFU / g≤total colony count≤2.5×10 5 CFU / g (preferably ≤2.0×10 5 CFU / g), defined as moderate contamination;

[0014] Solution 2: For severely contaminated potato flour, use hydrogen peroxide-microwave combined sterilization:

[0015] Adding hydrogen peroxide with a mass concentration of 2% to 8% to the whole potato flour, wherein the hydrogen peroxide accounts for 4.5 to 5.5% of the weight of the whole potato flour; the microwave intensity is 0.50 to 1.125 kW / kg, and the microwave sterilization time is 3.0 to 5.0 minutes;

[0016] 0.25×10 6 CFU / g≤total colony count≤1.2×10 6 CFU / g, defined as severe contamination.

[0017] As a further improvement of the sterilization method of potato whole flour of the present invention:

[0018] In the scheme 1: the surface temperature of the material is ≤86°C (79~86°C),

[0019] In the second scheme: the surface temperature of the material is ≤90°C (76-90°C).

[0020] As a further improvement of the sterilization method of potato whole flour of the present invention:

[0021] The potato flour is spread evenly and then sterilized by microwave, with the thickness of the spread being 1.3 to 1.5 cm.

[0022] As a further improvement of the sterilization method of potato whole flour of the present invention, in scheme 1:

[0023] The microwave intensity is 0.9~1.0875kW / kg, the microwave sterilization time is 4.5~5.0min; the material surface temperature is ≤86℃

[0024] (85~86℃).

[0025] As a further improvement of the sterilization method of potato whole flour of the present invention, in scheme 2:

[0026] Hydrogen peroxide is added to the potato flour by spraying while stirring, and then spread out (the thickness of the spread is 1.3-1.5 cm) for microwave sterilization.

[0027] As a further improvement of the sterilization method of potato whole flour of the present invention, in scheme 2:

[0028] The mass concentration of hydrogen peroxide in hydrogen peroxide is 6%, and the hydrogen peroxide accounts for 5% of the weight of the whole potato flour; the microwave intensity is 0.72-1.0 kW / kg, and the microwave sterilization time is 3.5-4.5 minutes; the surface temperature of the material is controlled to be ≤82°C (79°C-82°C)

[0029] Under the premise of not affecting the sensory characteristics and processing characteristics of potato flour, the present invention can reduce the total colony count of potato flour to 1.0×10 4 CFU / g or less. There is no obvious sensory difference between the potato flour before and after treatment, and it does not affect the color, aroma, taste, shape and other indicators of the finished potato chips.

[0030] The method of the invention can be used not only for sterilizing potato whole flour, but also for sterilizing other flour (wheat flour, rice flour, etc.) food raw materials.

[0031] The present invention has carried out the following experiments during the invention process:

[0032] Whole potato flour, moisture content ≤10%;

[0033] Household microwave oven: Lanshi P70F23P-G5(SO), microwave power 700W.

[0034] Experiment 1: Investigate the effect of microwave power and microwave time on the total number of bacterial colonies:

[0035] The experimental process is as follows:

[0036] 100g potato flour (total colony count 1.4×10 5 CFU / g) into a polyethylene composite film bag, try to make the potato flour flat in the bag, the thickness does not exceed 1.5cm. The plastic bag containing the sample is placed flat on the tray of a household microwave oven, and microwave heating is turned on. After the microwave ends and cools down, the total colony count of the potato flour is measured. The effect of microwave power and microwave time on the total colony count is investigated.

[0037] The experimental plan and results are shown in Table 1.

[0038] Table 1 Microwave sterilization condition screening experiment

[0039]

[0040]

[0041] Result analysis:

[0042] (1) Microwave sterilization is effective for whole potato flour. It can reduce the total colony count without affecting the sensory properties, achieving the initial goal of the project.

[0043] (2) Increasing microwave time and intensity can increase the microwave sterilization effect, but high intensity and long time sterilization will cause the potato starch to burn. The best microwave conditions are: low heat, 5 minutes.

[0044] Experiment 2: Microwave sterilization effect amplification experiment

[0045] In order to verify the sterilization effect of microwave sterilization on potato flour, a sterilization experiment was carried out on potato flour using production microwave equipment. This experiment was commissioned to Shanghai Lantai Microwave Equipment Co., Ltd., and the microwave equipment used in the experiment was a dynamic vacuum microwave drying equipment.

[0046] Experimental protocol:

[0047] Three batches of microwave sterilization demonstration tests were carried out according to the product weight to examine the microwave sterilization effect and equipment matching experiment. The experimental plan is shown in Table 2. During the experiment, the dynamic changes in the temperature on the surface and inside of the material, as well as the dehydration amount before and after microwave were recorded.

[0048] Table 2 Experimental design of microwave sterilization of whole potato flour

[0049] Experiment No. weight Microwave power Microwave time 1 4kg / basket, 20kg 0.87kW / kg 6min30s 2 2kg / basket, 12kg 1.45kW / kg 4min30s 3 2kg / basket, 16kg 1.0875kW / kg 10min

[0050] Experimental Results

[0051] During the experiment, the dynamic changes of the material surface temperature recorded by the infrared temperature measuring probe are shown in Table 3. The corresponding material status and total number of colonies after the set microwave time are listed in Table 4.

[0052] Table 3 Experimental phenomenon of microwave sterilization of potato flake flour

[0053]

[0054]

[0055] Table 4 Potato whole flour microwave sterilization experimental results

[0056]

[0057] Results Analysis

[0058] (1) The scale-up experiment proved that microwave sterilization is effective for whole potato flour. Without affecting the appearance of potato flour, microwave sterilization can reduce the total number of colonies and achieve the expected effect of the project.

[0059] (2) Under the same conditions, extending the microwave time can enhance the microwave sterilization effect, but the color of the potato starch becomes yellower. Therefore, it is advisable to further optimize the appropriate microwave intensity.

[0060] Experiment 3: Screening of auxiliary sterilization methods such as hydrogen peroxide

[0061] Hydrogen peroxide is a food processing aid permitted by GB2760, with no limit on dosage. Under microwave excitation and heating conditions, hydrogen peroxide can release oxygen free radicals, which can destroy the cell walls of microorganisms and have a bactericidal effect.

[0062] This experiment investigated the following auxiliary sterilization factors: (1) Material moisture content: verifying the effect of 5% and 10% water addition on microwave sterilization (experiment numbers 1-2); (2) The auxiliary effect of hydrogen peroxide on microwave sterilization (experiment numbers 3-5); (3) The possibility of inducing Bacillus subtilis spore germination and then killing it under high humidity conditions (experiment numbers 6-8).

[0063] Experimental protocol

[0064] Refer to Table 5 to design the levels of each auxiliary bactericidal factor. Potato whole flour: Tianshan Runda, total colony count 1.3×10 5 CFU / g.

[0065] Table 5 Auxiliary sterilization method screening experiment

[0066]

[0067] That is, numbers 1-6 are sterilized once, number 7 is sterilized twice, and number 8 is sterilized three times.

[0068] Experimental Results

[0069] Table 6 Auxiliary sterilization effect

[0070]

[0071]

[0072] Results Analysis

[0073] (1) After repeated verification, adding 10% water to whole potato flour can achieve a better sterilization effect, but adding water can cause the potato flour to clump.

[0074] (2) Hydrogen peroxide has a good sterilization effect on potato starch, but high doses of hydrogen peroxide cause the product to turn white and lose the unique aroma of potato starch. The optimal dose of hydrogen peroxide needs to be further optimized.

[0075] (3) It is extremely difficult to sterilize samples treated with high humidity (15% water addition), and intermittent multiple sterilizations cannot achieve the sterilization effect. Experiment 4: Tunnel-type continuous microwave sterilization experiment

[0076] Experimental process: Potato flour is added from the hopper and discharged from the flat outlet. As the conveyor belt moves, the potato flour is spread on the conveyor belt of the tunnel-type continuous microwave sterilization equipment. The width of the spread is 60cm, the thickness of the spread is about 1.5cm, the length of the sterilization tunnel cavity is 4.4m, and the total spread is 22kg. The power of the microwave equipment is 21.6kW, and the microwave sterilization intensity is 0.98kW / kg. The experimental plan and results are shown in Table 7.

[0077] Table 7 Tunnel microwave sterilization effect

[0078]

[0079]

[0080] It can be seen from Table 7 that the continuous microwave equipment has a total colony count of less than 2.0×10 5CFU / g potato whole powder has a good sterilization effect and can reduce the total number of colonies, but the sample color is slightly yellow. For seriously contaminated potato whole powder (No. 2), continuous microwave sterilization still did not achieve the expected effect.

[0081] Pilot tests have shown that for moderately contaminated potato flour, continuous microwave sterilization can effectively reduce the total colony count without affecting the appearance of the potato flour, thus achieving the expected effect of the project.

[0082] For severely contaminated whole potato flour, it is still necessary to screen effective auxiliary sterilization methods and cooperate with the use of microwave sterilization equipment. DETAILED DESCRIPTION

[0083] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0084] Example 1: For moderately contaminated potato flour (total colony count 1.4×10 5 CFU / g), specifically carry out the following steps:

[0085] The potato flour was sterilized by vacuum microwave drying equipment (maximum microwave power 17.4 kW), each hanging basket was spread with about 2-3 kg of material, the thickness of the material did not exceed 1.5 cm (about 1.3-1.5 cm), the number of hanging baskets varied between 3 and 6 to adjust the microwave intensity per unit weight of material, and the microwave power and time were set as shown in Table 8 below;

[0086] Table 8

[0087]

[0088]

[0089] “Color after sterilization”: “Normal” means that the color is basically the same as the original potato flour when observed with the naked eye.

[0090] The potato chips made from the sterilized potato flour of all the above groups (conventional formula as shown in Table 9, conventional processing method) had no significant difference in taste and color from the potato chips made from unsterilized potato flour.

[0091] Table 9 Potato chips recipe

[0092] Ingredients Scale(g) water 545.0 Potato flour 272.5 Modified starch 109.0 White sugar 28.6 Salt 3.3 additive 20.9 Shortening 24.5 total 1003.8g

[0093] Example 2: For heavily contaminated potato flour (total colony count 1.2×10 6 CFU / g), specifically carry out the following steps:

[0094] Prepare hydrogen peroxide of different concentrations (hydrogen peroxide concentration in hydrogen peroxide is 2-8%), add 5% hydrogen peroxide by spraying and stirring according to the weight of potato flour, and mix evenly. Then use dynamic vacuum microwave equipment to perform microwave sterilization as described in Example 1. The thickness of the material does not exceed 1.5 cm. The microwave power and time are set according to the loading amount as shown in Table 10 below;

[0095] Table 10

[0096]

[0097]

[0098] "Color after sterilization": "Normal" means that the color of the potato flour is basically the same as that of the original potato flour when observed with the naked eye. None of the groups described in Table 10 had lumps.

[0099] The sterilized potato flour obtained from the above group was used to make corresponding potato chips, and the taste and color of the potato chips were not significantly different from those made from unsterilized potato flour.

[0100] Comparative Example 1: The amount of hydrogen peroxide in Example 2 was changed from 5% to that described in Table 11 below. The effective amount of hydrogen peroxide and the experimental conditions were the same as those of Group 17 in Example 2. The results were shown in Table 11 below.

[0101] Table 11

[0102]

[0103]

[0104] Groups 3 and 4 both showed agglomeration.

[0105] Finally, it should be noted that the above examples are only some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. A method for sterilizing whole potato flour, characterized in that The following options are included: Solution 1: Use microwave sterilization for moderately contaminated potato flour: Option 2: For severely contaminated potato flour, use hydrogen peroxide-microwave combined sterilization.

2. The method for sterilizing whole potato flour according to claim 1, characterized in that: Solution 1: Use microwave sterilization for moderately contaminated potato flour: The microwave intensity is 0.75-1.45kW / kg, and the microwave sterilization time is 3.5-5.0min; 0.1×10 5 CFU / g≤total colony count≤2.5×10 5 CFU / g, defined as moderate contamination; Solution 2: For severely contaminated potato flour, use hydrogen peroxide-microwave combined sterilization: Adding hydrogen peroxide with a mass concentration of 2% to 8% to the whole potato flour, wherein the hydrogen peroxide accounts for 4.5 to 5.5% of the weight of the whole potato flour; the microwave intensity is 0.50 to 1.125 kW / kg, and the microwave sterilization time is 3.0 to 5.0 minutes; 0.25×10 6 CFU / g≤total colony count≤1.2×10 6 CFU / g, defined as severe contamination.

3. The method for sterilizing whole potato flour according to claim 2, characterized in that: In the scheme 1: the surface temperature of the material is ≤86°C, In the second scheme: the surface temperature of the material is ≤90°C.

4. The method for sterilizing whole potato flour according to claim 2 or 3, characterized in that: The potato flour is spread evenly and then sterilized by microwave, with the thickness of the spread being 1.3 to 1.5 cm.

5. The method for sterilizing whole potato flour according to claim 4, characterized in that In the first scheme: The microwave intensity is 0.9~1.1kW / kg.

6. The method for sterilizing whole potato flour according to claim 4, characterized in that In the second scheme: Hydrogen peroxide is added to the potato flour by spraying while stirring, and then the flour is spread out and sterilized by microwave.

7. The method for sterilizing whole potato flour according to claim 6, characterized in that In the second scheme: The mass concentration of hydrogen peroxide in hydrogen peroxide is 6%, and the hydrogen peroxide accounts for 5% of the weight of the whole potato flour; the microwave intensity is 0.72-1.0 kW / kg, and the microwave sterilization time is 3.5-4.5 minutes.

8. The method for sterilizing whole potato flour according to claim 7, characterized in that In the second scheme: Control the material surface temperature ≤82℃.

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