Preparation method of low-temperature vacuum fried oysters

Abstract

The invention discloses a preparation method of low-temperature vacuum fried oysters, and belongs to the technical field of food processing. The method comprises the following steps: uniformly mixing paste with an exogenous additive to prepare wrapping paste for later use; wherein the exogenous additive is any one of guar gum and xanthan gum; the method comprises the following steps: cleaning oysters, absorbing moisture on the surfaces of the oysters, firstly wrapping the oysters with a layer of wheat flour, then uniformly mixing the oysters with the wrapping paste, finally wrapping the mixture with breadcrumbs, processing the mixture into an oyster product, and performing vacuum frying to obtain the fried oyster product. The method solves the technical problems of low nutrient retention rate and high oxidation degree of fried oysters in the prior art, and has the advantages of cheap and easily available raw materials, easily controllable process conditions, remarkable quality improvement effect and the like, so that the fried oyster product is safer to eat and can be applied to large-scale production.

Description

Technical Field

[0001] The invention relates to a preparation method of low-temperature vacuum fried oysters, belonging to the technical field of food processing. Background Art

[0002] In recent years, the production and demand of oysters have shown a continuous upward trend. Oysters are rich in protein, zinc, iron, vitamin B12, omega-3 fatty acids and other nutrients, and have high nutritional value. Common ways of eating include eating raw meat, frying, and drying. The main products include ready-to-eat oysters, water bag oysters, canned oysters, etc., but there are fewer common fried oyster products.

[0003] Oyster fried products, its skin is coated with batter, forming a crispy shell during the frying process, and the oyster meat inside locks its own juice during the frying process. The fresh and juicy taste and crispy skin make it very suitable as a snack or a quick energy supplement. However, high-temperature processing often causes oxidation of oysters and loss of nutrients, which in turn leads to reduced product quality. In particular, oyster prepared foods often need to be reheated, which will cause more nutrient loss. Therefore, in view of this food quality issue, the development of natural, safe, healthy and effective fried oysters that can effectively improve the quality is a key technical issue that needs to be solved.

[0004] Vacuum frying is a frying process carried out in a vacuum environment. The vacuum degree is generally around 0.09MPa, and the frying temperature is usually controlled at 70℃-90℃. Compared with traditional high-temperature frying, on the one hand, it can better retain nutrients, avoid the loss of nutrients such as vitamins and proteins and the loss of bioactive components caused by high temperature, and reduce the risk of oil oxidation and the generation of harmful substances such as acrylamide; on the other hand, the product quality is excellent, the taste is crispy, the color is uniform and natural, and the product shelf life is extended due to sufficient dehydration and the formation of a grease isolation layer. However, in the vacuum low-temperature frying process, the dynamic change of the vacuum degree causes the atmospheric pressure to decrease, and this pressure change will produce a mechanical effect. In this process, the outer batter will be squeezed by the force generated by the pressure change when heated, and eventually the outer batter surface will rupture. Once the outer batter ruptures, its protective effect on the food will decrease, which may affect the taste, color and retention of nutrients of the food, and then have a negative impact on the product quality. Therefore, the optimization of the batter coating process and the full protection of the internal food quality have become the current research hotspots. Summary of the invention

[0005] [Technical issues]

[0006] In the prior art, oysters will lose nutrients during the high-temperature frying process; in the vacuum low-temperature frying process, the dynamic change of vacuum degree causes the atmospheric pressure to decrease, resulting in the outer batter being squeezed by the force generated by the pressure change when heated, which often causes the surface of the outer batter to rupture, further leading to a decrease in nutrients and product quality.

[0007] [Technical solution]

[0008] In order to solve the above technical problems, the purpose of the present invention is a method for preparing low-temperature vacuum fried oysters. The method effectively solves the problems of loss of nutrient components and quality degradation of products during high-temperature frying and vacuum low-temperature frying by adding colloids to the outer batter of oysters and combining the vacuum low-temperature frying process.

[0009] In order to achieve the above purpose, the technical solutions provided are as follows:

[0010] The present invention provides a method for preparing low-temperature vacuum fried oysters, the method comprising the following steps:

[0011] (1) mixing the batter and the exogenous additive uniformly to prepare an outer coating batter for later use; wherein the exogenous additive is any one of guar gum and xanthan gum;

[0012] (2) washing the oysters, drying the surface moisture, coating them with a layer of wheat flour, then mixing them evenly with the outer coating paste of step (1), and finally coating them with bread crumbs to produce oyster products;

[0013] (3) vacuum frying the oyster product of step (2) to obtain a fried oyster product.

[0014] In one embodiment, the amount of the exogenous additive added in step (1) is 0.2-0.5 wt % of the outer batter, and more preferably 0.2 wt %.

[0015] In one embodiment, the batter in step (1) is prepared by uniformly mixing wheat flour, corn starch, egg liquid and water components.

[0016] In one embodiment, the mass ratio of wheat flour, corn starch, egg liquid and water in the batter is 60:40:15-25:100-120.

[0017] In one embodiment, the oysters described in step (2) are fresh oyster meat.

[0018] In one embodiment, the mass ratio of the oyster product to frying oil in step (3) is 1:3-5.

[0019] In one embodiment, the vacuum frying in step (3) is vacuum low-temperature frying. Specifically, the frying temperature is 90-95°C, the frying time is 210-240 s, and the vacuum degree is 0.09 MPa.

[0020] In one embodiment, during the vacuum frying process in step (3), the defatting frequency is 100 Hz and the defatting time is 100 s.

[0021] In one embodiment, the parameters of the vacuum frying in step (3) are: the frying temperature is 95°C, the frying time is 210 s, the vacuum degree is 0.09 MPa, the defatting time is 100 s, and the defatting frequency is 100 Hz.

[0022] The present invention also provides a fried oyster product prepared by the above-mentioned preparation method.

[0023] The present invention also provides the application of the above-mentioned preparation method in the field of food processing.

[0024] [Beneficial effects]

[0025] (1) By synergistically applying commercially available guar gum and xanthan gum with low-temperature vacuum frying technology, the present invention innovatively constructs a "outer coating - low-temperature vacuum frying" dual protection system, effectively solving the technical problems of nutrient loss during the thermal processing of oysters and the damage to the integrity of the outer coating caused by pressure changes during the vacuum frying process. The exogenous additives have good thickening properties and will form a relatively stable protective film on the surface of the outer coating in the low-temperature vacuum frying environment, which can prevent the migration of nutrients to the oil phase during frying. At the same time, the exogenous additives increase the viscosity and toughness of the outer coating, enabling it to better maintain the structural integrity during pressure changes and not easily break or fall off, ensuring the appearance and quality of the fried oysters. The water content of the product is increased to 35.57±0.39% and 34.71±0.12%, the protein content is increased to 22.54±0.51% and 21.26±0.09%, the fat content is reduced to 5.29±0.04% and 5.56±0.07%, and the ash content is reduced to 0.97±0.02% and 1.00±0.02%;

[0026] (2) Using the method of the present invention can effectively reduce the degree of product oxidation, significantly inhibit the fat content of oysters, and is suitable for large-scale production. Moreover, the TBARs value of the fat content in the finished oyster product obtained by the method of the present invention is as low as 0.67±0.02 mg MDA / kg, the peroxide value is as low as 32.53±1.12, and the potassium iodate is as low as 0.57±0.03 mg / g; in terms of the degree of protein oxidation, the free sulfhydryl group content is as high as 72.47±6.70 μmol / g, the protein carbonyl content is as low as 6.72±0.23 μmol / mg, and the protein surface hydrophobicity is as low as 0.65±0.00 mg / g;

[0027] (3) The processing method of the fried oysters of the present invention has a simple process, low cost, and can obtain high-quality products with high nutritional content, and can effectively extend the shelf life of the fried oysters. Description of the Drawings

[0028] Figure 1 It is the appearance diagram of the samples after vacuum low-temperature frying treatment in Examples 1-2 and Comparative Examples 8-12. Detailed Embodiments

[0029] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope protected by the present invention. The following specific embodiments further describe the present invention.

[0030] The test methods involved in the present invention:

[0031] 1. Determination of texture

[0032] The oysters are cut into regular and consistent sizes. Each group of experiments is repeated at least three times, and the experimental conditions are always kept consistent. The texture is measured using a TA.XT.plus texture analyzer in TPA mode, with a trigger force of 5 g, a test speed set to 1 mm / s, and a compression ratio set to 75%.

[0033] 2. Determination of chromaticity

[0034] It is evaluated using an UltraScan Pro colorimeter in reflectance mode. The color difference represents the difference between the experimental group and the control group. The calculation formula for the color difference is as follows in Equation (1):

[0035] Color difference (ΔE) = ((a* - a) 2 + (b* - b) 2 + (L* - L) 2 ) 1 / 2 (1)

[0036] Wherein, a*, b*, and L* are the measured values of the experimental group; a, b, and L are the measured values of the control group.

[0037] 3. Determination of moisture content

[0038] Take a flat weighing bottle made of clean glass, place it in a drying oven at 101°C - 105°C, prop the bottle cap diagonally on the edge of the bottle, heat for 1.0 h, take it out, cover it, place it in a desiccator to cool for 0.5 h, weigh it, and repeat the drying until a constant weight is achieved. Weigh 2.00 g of the minced sample, put it into this weighing bottle, cover it, weigh it precisely, then place it in a drying oven at 101°C - 105°C, prop the bottle cap diagonally on the edge of the bottle, dry for 2 h - 4 h, cover it and take it out, place it in a desiccator to cool for 0.5 h and then weigh it. Then put it back into the drying oven to dry for about 1 h, take it out, place it in a desiccator to cool for 0.5 h and then weigh it again. When the mass difference between the two times is no more than 2 mg, it is a constant weight. The calculation formula for the moisture content is as follows in formula (2):

[0039] Moisture content (%) = (m1 - m2) / (m1 - m3) × 100% (2)

[0040] Wherein, m1 is the mass of the weighing bottle and the sample (g); m2 is the mass of the weighing bottle and the sample after drying (g); m3 is the mass of the weighing bottle (g).

[0041] 4. Determination of fat content

[0042] Use the Soxhlet extraction method: Accurately weigh about 2 g of the sample and put it into a filter paper thimble. Place the filter paper thimble containing the sample into the extraction thimble of the Soxhlet extractor, connect the receiving bottle that has been dried to a constant weight, add anhydrous ether or petroleum ether to about 2 / 3 of the volume of the receiving bottle. Heat under reflux and extract for about 8 hours until the extraction is complete. After the extraction is completed, remove the receiving bottle, recover the solvent, place the receiving bottle in a drying oven at 100°C - 105°C to dry for 1 - 2 hours, take it out and place it in a desiccator to cool to room temperature, weigh it, and repeat the drying until a constant weight is achieved. The calculation formula for the fat content is as follows in formula (3):

[0043] Fat content (%) = (m1 - m0) / m2 × 100% (3)

[0044] Wherein, m0 is the mass of the receiving bottle and the fat (g); m1 is the mass of the receiving bottle (g); m2 is the mass of the sample (g).

[0045] 5. Determination of protein content

[0046] Adopt the automatic Kjeldahl method: Accurately weigh 0.5 g of the sample and transfer it into a digestion tube. Add 0.2 g of copper sulfate, 6 g of potassium sulfate and 10 mL of sulfuric acid. Place the digestion tube in the digestion furnace of the automatic Kjeldahl apparatus, set the digestion program, first heat at 200 °C for 2 h. Then raise the temperature to about 420 °C and continue heating for 1.5 h (until the digestion solution becomes blue-green, clear and transparent). After digestion is completed, transfer the digestion tube to the automatic Kjeldahl apparatus. Set the program: dilution water volume 20 ml, 25 ml of 20 g / L boric acid, 40 ml of 400 g / L sodium hydroxide, distillation time 5 min, rinsing water volume 20 ml, and automatically start the distillation program. After absorption is completed, the titration device of the instrument will automatically titrate the absorption solution with a standard acid solution (such as 0.01 mol / L hydrochloric acid). Determine the titration end point by potentiometric titration or detecting the color change of the indicator, and record the volume of the acid consumed in the titration. The calculation formula for the protein content is as follows in formula (4):

[0047] Protein content (%) = ((V1 - V2) × c × 0.0140 × F / (m × V3 / 100)) × 100% (4)

[0048] Wherein, V1 is the volume (ml) of the sulfuric acid standard solution consumed by the sample; V2 is the volume (ml) of the sulfuric acid standard solution consumed by the blank; c is the concentration (mol / L) of the hydrochloric acid standard solution; 0.0140 is the millimolar mass of nitrogen (g / mmol); F is the protein conversion factor (6.25 for general foods, 6.38 for pure milk and pure dairy products, 5.70 for flour, etc.); m is the mass (g) of the sample; V3 is the volume (ml) of the digested solution taken

[0049] 6. Determination of ash content

[0050] Take an appropriate amount of the sample, 2 g, accurate to 0.0001 g. Place the sample in a crucible that has been weighed to a constant weight, and carefully heat it on an electric furnace to fully carbonize the sample until there is no smoke. Then place the crucible in a muffle furnace and burn it at 550 °C - 600 °C for 4 hours. After the burning is completed, turn off the power of the muffle furnace. When the temperature drops to about 200 °C, take out the crucible, place it in a desiccator and cool it to room temperature, then weigh it. Then put it back into the muffle furnace and burn it for 1 hour, take it out and cool it to weigh it. Repeat this operation until a constant weight is achieved (the difference in mass between two weighings does not exceed 0.5 mg). The calculation formula for the ash content is as follows in formula (5):

[0051] Ash content (%) = (m1 - m2) / (m1 - m3) × 100% (5)

[0052] Wherein, m1 is the mass (g) of the crucible and the sample; m2 is the mass (g) of the crucible and the dried sample; m3 is the mass (g) of the crucible.

[0053] 7. Determination method of fat oxidation

[0054] (1) TBARS value: The thiobarbituric acid solution used consists of 2-thiobarbituric acid with a concentration of 0.375%, trichloroacetic acid with a concentration of 15%, and hydrochloric acid solution with a concentration of 0.25 mol / L. The specific method is as follows: Add 1 g of crushed oyster meat to 5 mL of the thiobarbituric acid solution, then heat it in a boiling water bath for 20 minutes, cool it with running water, and centrifuge it at 8000 r / min for 15 min at 4°C. Measure the absorbance of the supernatant at 532 nm; The calculation formula for the TBARS value of the degree of lipid oxidation is as follows in formula (6):

[0055] TBARS (mg / kg) = A 532 ×2.77 (6)

[0056] Where, A532 is the absorbance of the supernatant at 532 nm.

[0057] Where, V1 is the volume consumed at the titration end point (ml); V2 is the volume consumed by deionized water titration (ml); m is the oil mass (g).

[0058] (2) Peroxide value: Soak and extract the oil to be tested with petroleum ether twice the volume of the oyster sample for 12 h, filter to obtain the liquid and perform rotary evaporation at 30°C until dry to obtain the oil sample. Accurately weigh 0.1 g of the extracted oil sample and vortex mix it with 3 mL of isooctane. Take 50 μL of the solution to be tested and mix it with 1.45 m prepared methanol-n-butanol (2:1), 10 μL of ammonium thiocyanate solution (1 g / mL), and 10 μL of fresh ferrous chloride solution (reacted with 0.81 g of barium chloride and 1 g of ferrous sulfate in 0.5 mo1 / L HC1, let it stand in the dark, and take the supernatant). React for 20 minutes in the dark and measure the absorbance value at 510 nm. The calculation formula for the peroxide value of the degree of lipid oxidation is as follows in formula (7):

[0059] Peroxide value = [(A 510 +0.0172) / 0.8094]×60(7)

[0060] Where, A 510 is the absorbance of the supernatant at 510 nm.

[0061] (3) Acid value: The method for determining the acid value is based on GB5009.229-2016. Titrate 50 mL of deionized water (containing 3 drops of phenolphthalein indicator) with a calibrated 0.1 mo1 potassium hydroxide solution until it turns pink. Dissolve the extracted oil in 50 mL of an ether-isopropanol mixed solution, add 4 drops of thymol blue indicator and shake well. Titrate the mixture with the potassium hydroxide standard solution until it turns blue. The calculation formula for the acid value of the degree of lipid oxidation is as follows in formula (8):

[0062] Potassium acid content = (V1 - V2)×C KIt is \(56.1 / m(8)\)

[0063] where \(m\) is the mass of the oil.

[0064] 8. Determination method of protein oxidation

[0065] (1) Determination of myofibril protein (MP)

[0066] Homogenize 7 g of the minced sample with 4 volumes of buffer (pH 7.0, containing 0.1 M NaCl, 2 mM MgCl2, 1 mM EGTA, 10 mM NaH2PO4-Na2HPO4) for 60 s. Then centrifuge the homogenate at 10000×g for 10 minutes, collect the precipitate, and wash it twice with four volumes of the same buffer under the same centrifugation conditions. Collect the precipitate again and wash it twice with 0.1 M NaCl to obtain MP. Dissolve MP in phosphate buffer (pH 7.0, containing 0.6 M NaCl, 15 mM NaH2PO4-Na2HPO4), and store it at 4°C for no more than 24 h. Determine the MP content using the biuret method.

[0067] (2) Determination of free sulfhydryl group content

[0068] Mix 0.5 mL of 4 mg / mL MP solution with 4.5 mL of solution (pH 8.0, containing 0.2 M Tris-HCl, 8 M urea, 3 mM EDTA, 1% SDS (w:v), 0.1 M Na2SO3). Then, add 0.5 mL (pH 9.5, containing 0.2 M Tris-HCl, 8 M urea, 3 mM EDTA, 1% SDS (w:v), 0.1 M Na2SO3, 10 mM 2-nitro-5-thiobenzoate (NTSB)) to 4 mL of the mixture, and incubate at 40°C for 20 min. Read the absorbance of the mixture at 412 nm, and the disulfide bond content is expressed in mol / 10 -5 g of protein.

[0069] (3) Determination of protein carbonyl content

[0070] The protein carbonyl content detection kit was used to determine the oxidation of oyster protein by calculating the carbonyl content. Specifically: Add 1 mL of the extraction solution (acidic buffer) in the kit to 0.1 g of oyster sample, homogenize thoroughly, and centrifuge at 5000 r / min at 4°C for 10 min; Take the supernatant to 0.1 mL of reagent 1 in the kit, let it stand at room temperature for 10 minutes, and then centrifuge at 12000 r / min at 4°C for 10 minutes; The supernatant is used as the sample and determined according to the steps in the kit instructions.

[0071] (4) Determination of surface hydrophobicity

[0072] Add 200 μL of 1 mg / mL bromophenol blue solution to 1 mL of 4 mg / mL MP solution, homogenize for 60 s, and centrifuge at 2000×g for 15 minutes. Dilute the supernatant 20 times and measure the absorbance at 595 nm. The surface hydrophobicity is expressed as the amount of bromophenol blue bound (μg).

[0073] Example 1

[0074] A method for low-temperature vacuum frying of oysters, comprising the following steps:

[0075] (1) Remove the shells of fresh oysters to obtain the meat, wash it, and refrigerate the oyster meat with the surface moisture absorbed for later use;

[0076] (2) Make an outer coating paste by mixing 60 g of wheat flour, 40 g of corn starch, 21.67 g of egg liquid, and 108.33 g of purified water, and then add 0.46 g of guar gum and mix evenly to obtain an outer coating paste containing guar gum; wherein, the addition amount of guar gum is 0.2 wt% of the outer coating paste;

[0077] (3) First coat the oyster meat in step (1) with a layer of wheat flour, and then mix it evenly with the outer coating paste containing guar gum in step (2) until it is completely wrapped, and then coat it with breadcrumbs on the outside;

[0078] (4) Place the oysters coated with breadcrumbs in step (3) in a low-temperature vacuum fryer, with a frying temperature of 95 °C, a frying time of 210 s, a vacuum degree of 0.09 MPa, a defatting time of 100 s, and a defatting frequency of 100 Hz to obtain the finished coated fried oysters.

[0079] Example 2

[0080] A method for low-temperature vacuum frying of oysters, comprising the following steps:

[0081] (1) Remove the shells of fresh oysters to obtain the meat, wash it, and refrigerate the oyster meat with the surface moisture absorbed for later use;

[0082] (2) Make an outer coating paste by mixing 60 g of wheat flour, 40 g of corn starch, 21.67 g of egg liquid, and 108.33 g of purified water, and then add 0.46 g of xanthan gum and mix evenly to obtain an outer coating paste containing xanthan gum; wherein, the addition amount of xanthan gum is 0.2 wt% of the outer coating paste;

[0083] (3) First coat the oyster meat in step (1) with a layer of wheat flour, and then mix it evenly with the outer coating paste containing xanthan gum in step (2) until it is completely wrapped, and then coat it with breadcrumbs on the outside;

[0084] (4) Place the oysters coated with breadcrumbs in step (3) into a low-temperature vacuum fryer. Fry at a temperature of 95 °C for 210 s, with a vacuum degree of 0.09 MPa, a defatting time of 100 s, and a defatting frequency of 100 Hz to obtain the finished product of breaded and fried oysters.

[0085] Comparative Example 1 (without colloid, only low-temperature vacuum frying)

[0086] A method for low-temperature vacuum frying oysters, comprising the following steps:

[0087] (1) Remove the shells of fresh oysters to obtain the meat, wash it, and refrigerate the oyster meat with the surface moisture absorbed for later use.

[0088] (2) Make an outer coating paste with 60 g of wheat flour, 40 g of corn starch, 21.67 g of egg liquid, and 108.33 g of purified water.

[0089] (3) First coat the oyster meat in step (1) with a layer of wheat flour, then mix it evenly with the outer coating paste in step (2) until completely wrapped, and then coat it with breadcrumbs on the outside.

[0090] (4) Place the oysters coated with breadcrumbs in step (3) into a low-temperature vacuum fryer. Fry at a temperature of 95 °C for 210 s, with a vacuum degree of 0.09 MPa, a defatting time of 100 s, and a defatting frequency of 100 Hz to obtain the finished product of breaded and fried oysters.

[0091] Comparative Example 2 (with colloid, fried in an atmospheric pressure fryer)

[0092] (1) Remove the shells of fresh oysters to obtain the meat, wash it, and refrigerate the oyster meat with the surface moisture absorbed for later use.

[0093] (2) Make an outer coating paste with 60 g of wheat flour, 40 g of corn starch, 21.67 g of egg liquid, and 108.33 g of purified water, and then add 0.46 g of guar gum and mix evenly to obtain an outer coating paste containing guar gum; wherein, the addition amount of guar gum is 0.2 wt% of the outer coating paste.

[0094] (3) First coat the oyster meat in step (1) with a layer of wheat flour, then mix it evenly with the outer coating paste containing guar gum in step (2) until completely wrapped, and then coat it with breadcrumbs on the outside.

[0095] (4) Place the oysters coated with breadcrumbs in step (3) into an atmospheric pressure fryer and fry at 180 °C for 3.5 min to obtain the finished product of breaded and fried oysters.

[0096] Comparative Example 3 (with colloid, fried in an atmospheric pressure fryer)

[0097] (1) Remove the shells from fresh oysters, take out the meat, wash it, and refrigerate the oyster meat with the surface moisture absorbed for later use;

[0098] (2) Make an outer coating paste by mixing 60 g of wheat flour, 40 g of corn starch, 21.67 g of egg liquid, and 108.33 g of purified water. Then add 0.46 g of xanthan gum and mix evenly to obtain an outer coating paste containing xanthan gum; among them, the addition amount of xanthan gum is 0.2 wt% of the outer coating paste;

[0099] (3) First coat the oyster meat in step (1) with a layer of wheat flour, and then evenly mix it with the outer coating paste containing xanthan gum in step (2) until it is completely wrapped. Then coat it with breadcrumbs on the outside;

[0100] (4) Place the oysters coated with breadcrumbs in step (3) in an atmospheric fryer and fry at 180 °C for 3.5 min to obtain the finished coated and fried oysters.

[0101] Control Example 4 (without colloid, fried in an air fryer)

[0102] (1) Remove the shells from fresh oysters, take out the meat, wash it, and refrigerate the oyster meat with the surface moisture absorbed for later use;

[0103] (2) Mix 60 g of wheat flour, 40 g of corn starch, 21.67 g of egg liquid, and 108.33 g of purified water evenly to make an outer coating paste for later use;

[0104] (3) First coat the oyster meat in step (1) with a layer of wheat flour, and then evenly mix it with the outer coating paste in step (2) until it is completely wrapped. Then coat it with breadcrumbs on the outside;

[0105] (4) Place the oysters coated with breadcrumbs in step (3) in an air fryer and fry at 180 °C for 8 min, turning them over every 4 min to obtain the finished coated and fried oysters.

[0106] Control Example 5 (with colloid, fried in an air fryer)

[0107] (1) Remove the shells from fresh oysters, take out the meat, wash it, and refrigerate the oyster meat with the surface moisture absorbed for later use;

[0108] (2) Make an outer coating paste by mixing 60 g of wheat flour, 40 g of corn starch, 21.67 g of egg liquid, and 108.33 g of purified water. Then add 0.46 g of guar gum and mix evenly to obtain an outer coating paste containing guar gum; among them, the addition amount of guar gum is 0.2 wt% of the outer coating paste;

[0109] (3) First coat the oyster meat in step (1) with a layer of wheat flour, and then evenly mix it with the outer coating paste containing guar gum in step (2) until it is completely wrapped. Then coat it with breadcrumbs on the outside;

[0110] (4) Place the oysters coated with breadcrumbs in step (3) into an air fryer and fry at 180°C for 8 minutes, turning them over every 4 minutes, to obtain the finished product of batter-fried oysters.

[0111] Comparative Example 6 (without colloid, conventional frying)

[0112] (1) Remove the shells from fresh oysters, take out the meat, wash it, and refrigerate the oyster meat with the surface moisture absorbed for later use.

[0113] (2) Make an outer batter by mixing 60 g of wheat flour, 40 g of corn starch, 21.67 g of egg liquid, and 108.33 g of purified water.

[0114] (3) First coat the oyster meat in step (1) with a layer of wheat flour, then mix it evenly with the outer batter in step (2) until it is completely wrapped, and then coat it with breadcrumbs on the outside.

[0115] (4) Place the oysters coated with breadcrumbs in step (3) into a conventional frying pan and fry at 180°C for 3.5 minutes to obtain the finished product of batter-fried oysters.

[0116] Comparative Example 7 (without colloid, air fryer)

[0117] (1) Remove the shells from fresh oysters, take out the meat, wash it, and refrigerate the oyster meat with the surface moisture absorbed for later use.

[0118] (2) Mix 60 g of wheat flour, 40 g of corn starch, 21.67 g of egg liquid, and 108.33 g of purified water evenly to make an outer batter and set it aside.

[0119] (3) First coat the oyster meat in step (1) with a layer of wheat flour, then mix it evenly with the outer batter in step (2) until it is completely wrapped, and then coat it with breadcrumbs on the outside.

[0120] (4) Place the oysters coated with breadcrumbs in step (3) into an air fryer and fry at 180°C for 8 minutes, turning them over every 4 minutes, to obtain the finished product of batter-fried oysters.

[0121] Comparative Example 8

[0122] The difference from Example 1 is only that the guar gum in step (2) is replaced with edible gelatin; other parameters and conditions are the same as those in Example 1.

[0123] Comparative Example 9

[0124] The difference from Example 1 is only that the guar gum in step (2) is replaced with pectin; other parameters and conditions are the same as those in Example 1.

[0125] Comparative Example 10

[0126] The difference from Example 1 is only that the guar gum in step (2) is replaced with sodium alginate; other parameters and conditions are the same as those in Example 1.

[0127] Comparative Example 11

[0128] The difference from Example 1 is only that the guar gum in step (2) is replaced with carrageenan; other parameters and conditions are the same as those in Example 1.

[0129] Comparative Example 12

[0130] The difference from Example 1 is only that the guar gum in step (2) is replaced with low-substituted hydroxypropyl cellulose; other parameters and conditions are the same as those in Example 1.

[0131] Comparative Example 13

[0132] The difference from Example 1 is only that the guar gum in step (2) is replaced with sodium polyacrylate; other parameters and conditions are the same as those in Example 1.

[0133] Result Analysis

[0134] 1. Figure 1 It is the appearance of the samples after different exogenous additives are added to the outer batter and processed by collaborative vacuum low-temperature frying. It can be Figure 1 clearly seen that the structural integrity of the outer batter is maintained after adding guar gum and xanthan gum, and it has a better protection effect compared with Comparative Examples 8 - 12.

[0135] 2. The texture and chromaticity of the batter-fried oysters obtained from Examples 1 - 2 and Comparative Examples 1 - 7 were measured, and the measurement results are shown in Table 1 and Table 2;

[0136] Table 1 Texture test results of the samples in Examples 1 - 2 and Comparative Examples 1 - 7

[0137]

[0138] It can be seen from Table 1 that the average values of the comparative example samples in terms of hardness, brittleness, elasticity, cohesiveness, gumminess, and chewiness are generally higher than those of the examples, showing that they are harder, more brittle, stronger in elasticity and viscosity, and have greater chewing resistance; after vacuum low-temperature frying treatment, the example samples are relatively softer, easier to chew, and less sticky.

[0139] Table 2 Chromaticity test results of the samples in Examples 1 - 2 and Comparative Examples 1 - 7

[0140]

[0141] As can be seen from Table 2: in terms of a* value, the red hue of the comparative products is more obvious, and Example 1 has the lowest red hue; in terms of b* value, comparative examples 4, 5, and 7 have higher b* values ​​and are more yellowish, among which Example 2 has the lowest b* value and the yellow hue is not prominent; in terms of L* value, the overall brightness level of the comparative examples is relatively high, and Example 2 has the lowest brightness; the ΔE value shows that the color difference between Example 2 and Comparative Example 6 is obvious, while the color difference between Example 1 and Comparative Example 6 is small, indicating that vacuum low-temperature frying after adding guar gum will cause the oyster product to change less than that of normal pressure frying, while the difference of xanthan gum is large.

[0142] 3. The appearance, nutritional components and oxidation degree of the batter-fried oysters obtained in the examples and comparative examples were measured. The results are shown in Table 3:

[0143] Table 3 Basic physical and chemical index test results of samples in Examples 1 to 2 and Comparative Examples 1 to 7

[0144]

[0145] It can be seen from Table 3 that in terms of moisture content, compared with Comparative Examples 1 to 7, adding guar gum and xanthan gum to the outer batter and coordinating vacuum low-temperature frying can better retain the moisture content of oysters in Examples 1 to 2, and the maximum moisture retention rates are 35.57±0.39% and 34.71±0.12%, respectively, which are increased by 11.05% and 8.37% compared with Comparative Example 6.

[0146] In terms of protein content, vacuum low-temperature frying can better retain the protein content of oysters, and the protein content is higher after adding guar gum and xanthan gum, reaching 22.54±0.51% and 21.26±0.09%, respectively, which is 25.21% and 18.14% higher than that of comparative example 6;

[0147] In terms of fat content, the addition of guar gum and xanthan gum can reduce the fat content of oysters, and the lowest fat content after low-temperature vacuum frying is 5.29±0.04% and 5.56±0.07%, respectively, which is 10.82% and 6.35% lower than that of the control group 6 (5.94±0.08%);

[0148] In terms of ash content, the addition of guar gum and xanthan gum reduced the ash content of oysters, and the vacuum low-temperature frying reduced it most significantly, reaching 0.97±0.02% and 1.00±0.02%, respectively, which was 22.72% and 20.87% lower than that of comparative example 6. It can be seen that vacuum low-temperature frying can retain the nutritional components of oysters, and the addition of guar gum and xanthan gum has a better retention effect.

[0149] 4. The lipid oxidation degree of the batter-fried oysters obtained in the examples and comparative examples was measured. The results are shown in Table 4:

[0150] Table 4 Test results of lipid oxidation degree of samples in Examples 1-2 and Comparative Examples 1-7

[0151]

[0152] As can be seen from Table 4: Compared with Comparative Examples 1-7, the TBARs value of oysters after vacuum low-temperature frying in Examples 1-2 decreased significantly. The value of adding guar gum was the lowest at 0.67±0.02 (mg MDA / Kg), and the value of adding xanthan gum was the second lowest at 0.86±0.01 (mg MDA / Kg); After vacuum low-temperature frying treatment, the peroxide value of oysters can be significantly reduced. The value of adding guar gum was the lowest at 32.53±1.12, and the value of adding xanthan gum was the second lowest at 33.81±0.82; After vacuum low-temperature frying treatment, the acid value of oysters can be significantly reduced. The value of adding xanthan gum was the lowest at 0.58±0.05 (mg / g), and the value of adding guar gum was the second lowest at 0.57±0.03 (mg / g). It can be seen that vacuum low-temperature frying treatment can reduce the lipid oxidation degree of oysters, and the inhibitory effect of adding guar gum and xanthan gum is better.

[0153] 5. Measure the protein oxidation degree of the batter-fried oysters obtained in the examples and comparative examples, and the results are shown in Table 5:

[0154] Table 5 Test results of protein oxidation degree of samples in Examples 1-2 and Comparative Examples 1-7

[0155]

[0156] As can be seen from Table 5: Compared with Comparative Examples 1-7, the content of free sulfhydryl groups in oysters after vacuum low-temperature frying in Examples 1-2 increased significantly. The value of adding xanthan gum was 72.47±6.70 (μmol / g), and the value of adding guar gum was the second lowest at 71.29±2.79 (μmol / g); After vacuum low-temperature frying treatment, the protein carbonyl content can be significantly reduced. The value of adding guar gum was the lowest at 6.72±0.23 (μmol / mg), and the value of adding xanthan gum was the second lowest at 7.00±0.02 (μmol / mg); After vacuum low-temperature frying treatment, the surface hydrophobicity of oyster protein can be significantly reduced. The value of adding xanthan gum was the lowest at 0.65±0.00 (mg / g), and the value of adding guar gum was the second lowest at 0.67±0.02 (mg / g). It can be seen that vacuum low-temperature frying treatment can reduce the protein oxidation degree of oysters, and the inhibitory effect of adding guar gum and xanthan gum is better.

[0157] The examples provided above are not intended to limit the scope covered by the present invention, nor are the described steps intended to limit their execution order. Obvious improvements made by those skilled in the art to the present invention in combination with the existing common general knowledge also fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing low-temperature vacuum fried oysters, characterized in that: The preparation method comprises the following steps: (1) mixing the batter and the exogenous additive uniformly to prepare an outer coating batter for later use; wherein the exogenous additive is any one of guar gum and xanthan gum; (2) washing the oysters, drying the surface moisture, coating them with a layer of wheat flour, then mixing them evenly with the outer coating paste of step (1), and finally coating them with bread crumbs to produce oyster products; (3) vacuum frying the oyster product of step (2) to obtain a fried oyster product.

2. The preparation method according to claim 1, characterized in that: The amount of the exogenous additive added in step (1) is 0.2-0.5 wt % of the outer paste.

3. The preparation method according to claim 1, characterized in that: The batter described in step (1) is prepared by uniformly mixing wheat flour, corn starch, egg liquid and water components.

4. The preparation method according to claim 3, characterized in that: The mass ratio of wheat flour, corn starch, egg liquid and water in the batter is 60:40:15-25:100-120.

5. The preparation method according to claim 1, characterized in that: In step (3), the mass ratio of the oyster product to the frying oil is 1:3-5.

6. The preparation method according to claim 1, characterized in that: The vacuum frying in step (3) is vacuum low-temperature frying, specifically, the frying temperature is 90-95° C., the frying time is 210-240 s, and the vacuum degree is 0.09 MPa.

7. The preparation method according to claim 1, characterized in that: During the vacuum frying process in step (3), the de-oiling frequency is 100 Hz and the de-oiling time is 100 s.

8. The preparation method according to claim 1, characterized in that: The parameters of the vacuum frying in step (3) are: frying temperature of 95° C., frying time of 210 s, vacuum degree of 0.09 MPa, deoiling time of 100 s, and deoiling frequency of 100 Hz.

9. The fried oyster product prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the preparation method according to any one of claims 1 to 8 in the field of food processing.

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