CN108399467A - A method of prediction stewed duck with bean sauce shelf life - Google Patents

Abstract

The invention discloses a kind of methods of prediction stewed duck with bean sauce shelf life, the index of quality of seasoned duck product to being stored under different temperatures is studied, total plate count, coliform, mould, acid value, peroxide value, production of thiobarbituric acid reactive and organoleptic quality by measuring stewed duck with bean sauce filter out the quality comparison key index of stewed duck with bean sauce storage period further according to Pearson correlation analysis as Time Change determines stewed duck with bean sauce quality comparison kinetic model：Mould and TBARS, and changing rule meets zero order kinetics model.And according to the shelf life forecasting model of stewed duck with bean sauce index of quality mould and TBARS value combination Arrhenius establishing equation stewed duck with bean sauce.The present invention can quickly and effectively predict the remaining shelf life of the stewed duck with bean sauce in 0~40 DEG C of temperature range, cost-effective to carry out respective handling to the seasoned duck product of different freshness in time to provide guidance in storage transport and sales process.

Description

A method of predicting the shelf life of sauced duck

(1) Technical field

The invention relates to a method for predicting the shelf life of the sauced duck, in particular suitable for the prediction of the shelf life of the sauced duck during storage, transportation and sales.

(2) Background technology

Duck meat is delicious and tender, rich in nutrition, has the advantages of low fat, low cholesterol, high protein, etc., and is rich in vitamins, inorganic salts and trace elements. Traditional duck meat products in my country mainly include roast duck, salted duck, salted duck and sauce duck. Sauce duck is favored by consumers because of its tender meat and unique flavor. However, because sauced duck is a traditional cured product, there is currently no means of accurately predicting its remaining shelf life in the market.

The total number of colonies, coliforms, mold, acid value, peroxide value, and thiobarbituric acid reaction products (TBARS) are important indicators of the quality change of sauced duck, which can reflect the freshness and spoilage of sauced duck in different aspects . The total number of bacterial colonies, coliform bacteria, and mold in the microbial indicators can reflect the situation of food contamination by microorganisms. The higher the microbial load, the more severe the food corruption. The acid value, peroxide value and TBARS in the lipid oxidation index can well reflect the degree of fat oxidation rancidity. Among them, TBARS reflects the gradual oxidation and hydrolysis of unsaturated fatty acids in sauced duck, producing low-level aldehydes and ketones that react with thiobarbituric acid to form stable red compounds. The darker the color, the higher the degree of corruption in sauced duck. The peroxide value is an index indicating the degree of hydroperoxide produced in the initial stage of fatty acid oxidation. Generally, the higher the peroxide value, the worse the quality of the sauced duck. Acid value is an index used to indicate the degree of lipid hydrolysis rancidity. The higher the acid value, the higher the free fatty acid content produced by lipid hydrolysis.

At present, kinetic models are widely used in the research of food shelf life models. Han et al. used the Arrhenius equation to establish a shelf-life prediction model for beef; Dalcanton et al. and Torrieri et al. studied the shelf-life prediction models for pork and Italian sausage under different temperature storage conditions. There are few domestic studies on the shelf life of sauced duck. Therefore, how to quickly and effectively evaluate the quality changes of sauced duck products during storage and accurately predict their shelf life is particularly important.

(3) Contents of the invention

The purpose of the present invention is to provide a method for predicting the shelf life of sauced duck. Through the analysis of various physical and chemical indicators, a prediction model for the shelf life of sauced duck at 0-40°C is proposed to be established, and each index under the conditions of 4, 25, and 37°C is used for comparison. The model is verified, and the comprehensive comparison of the zero-order kinetic model and the first-order kinetic model is more suitable for the prediction of the shelf life of the sauced duck in this temperature range, so as to monitor the quality changes of the sauced duck in the logistics and storage process in real time, thereby reducing losses and reduce economic losses.

The technical scheme adopted in the present invention is:

The invention provides a method for predicting the shelf life of sauced duck, and the characteristic indexes (total number of colonies, coliform group, mold, acid value, peroxide value, thiobarbituric acid reaction product) of sauced duck under different temperature storage conditions are provided. (TBARS)) changes and sensory quality were studied, and the indicators with the best correlation with sensory quality under various temperature conditions were selected through Pearson correlation analysis, and then the key indicators mold and TBARS were selected, combined with the zero-order kinetic model and The first-order kinetic model selects the mold and TBARS kinetic model with the best correlation under different temperature conditions, and combines the Arrhenius equation to establish a prediction model for the shelf life of sauced duck. The steps are as follows:

1) Transport the repurchased sauced duck (raw product) to the laboratory, and put the sauced duck into vacuum packaging bags (sterilization condition 121°C, 15min) on the aseptic operation table;

2) The packaged sauced ducks were randomly divided into three groups, stored at 4, 25, and 37°C, and samples were taken at certain time intervals to determine mold and thiobarbituric acid reaction products (TBARS);

3) According to the change of mold and TBARS with time, the kinetic model of mold and TBARS changes with temperature is established;

4) Utilize the Arrhenius equation to analyze the temperature T and the reaction rate constant k to obtain the pre-exponential factor A ₀ and the reaction activation energy Ea of the key indicators of the sauced duck;

5) In combination with the kinetic model, the shelf-life prediction models based on the key indicators mold and TBARS were established at 4-37°C:

In the formula, SL is the remaining shelf life, d; B ₀ is the initial value of mold or TBARS; B is the measured value of mold or TBARS at a certain time; A ₀ is the pre-exponential (frequency) factor, that is, the reaction rate when the activation energy is zero ; Ea is the activation energy, J/mol; R is the gas constant, 8.3144J/(mol K); T is the absolute temperature, K;

6) Validation and selection of shelf life prediction models.

Further, the present invention designs the sampling time interval to take a sample every 7 days.

Further, combined with the national standard, after comprehensively considering the sensory evaluation of the sauced duck, it is determined that the total number of molds at the end of the shelf life of the sauced duck is 10000 CFU/g, and the TBARS value is 2.0 mg/kg.

Furthermore, the zero-order kinetic model and the first-order kinetic model were used to perform regression analysis on the total number of molds and TBARS of sauced duck at different temperatures, and the regression coefficient R ² was compared to determine that the quality change of sauce duck was a zero-order kinetic model.

Further, curve fitting was carried out on the rate response constant k at different temperatures to obtain the change activation energy of the total number of sauced duck molds and the TBARS value were 16034.13 and 25809.98 kJ/mol, and the pre-exponential factor k ₀ were 165097.25 and 1072.32, respectively, and then obtained the mold-based The shelf life prediction model of:

Predictive models based on TBARS values:

SL(Mould) and SL(TBARS) are sauced duck mould, respectively, and the remaining shelf life of TBARS model, d.

0-40°C is the temperature range that the sauced duck may experience after being stored and transported, from being placed on the supermarket shelf to when the consumer buys it home. The present invention can predict the remaining shelf life within this temperature range.

The present invention synthesizes various indicators such as sensory, total number of colonies, coliforms, mold, acid value, peroxide value, thiobarbituric acid reaction products (TBARS) and other indicators of sauced duck, and selects key indicators through Pearson correlation analysis : After mold and TBARS, the key indicators mold and TBARS when judging the end of the shelf life of sauced duck were determined.

Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

Through the Pearson correlation analysis, the present invention screens out the mold and TBARS, the key indicators that can evaluate the quality of sauce duck products, from many quality evaluation indicators of sauce duck products, and establishes a method for predicting the shelf life of sauce duck based on mold and TBARS, which can be more quickly and accurately. Predict the freshness and remaining shelf life of the sauced duck, and provide guidance for the storage, transportation and sales process, so that the sauced duck with different freshness can be dealt with in time to save costs.

(4) Description of drawings

Fig. 1 The physical, chemical and microbial sampling distribution diagram of sauced duck. (1) AV, POV and TBARS. (2) Microbial value (total bacteria count, Escherichia coli, mold) and color difference.

Figure 2 Changes in the total number of bacterial colonies in sauced duck stored at different temperatures.

Fig. 3 Changes of coliform bacteria in soy sauce duck stored at different temperatures.

Figure 4 Changes of mold in sauced ducks stored at different temperatures.

Figure 5 Changes in the acid value of duck sauce stored at different temperatures.

Figure 6 Changes in the peroxide value of sauced duck stored at different temperatures.

Fig. 7 Changes in TBARS of sauced duck stored at different temperatures.

Figure 8 Changes in the overall sensory score of sauced duck stored at different temperatures, a appearance color score b odor score c tissue state.

(5) Specific implementation methods

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

Example 1

1 Experimental materials and main equipment

1.1 Raw materials and pretreatment

Put 30 sauced ducks (about 500g each) into a sterilized PA/CPP composite material vacuum packaging bag (sterilization condition 121°C, 15min) on the aseptic operating table at 4, 25, and 37°C Storage (37°C for destruction test, 25°C for normal temperature test and 4°C for control experiment), samples were taken after 0, 7, 14, 21, and 28 days for determination. For each measurement, 2 sauced ducks were randomly sampled, and the total colony count, Escherichia coli, mold, peroxide value, acid value, and thiobarbituric acid reaction product value were measured under the aseptic operating table. In order to reduce the differences in detection indicators caused by different sampling locations, the sampling locations for each indicator in the test are shown in Figure 1. The breast meat of sauced duck was used for the determination of fat oxidation index, and the leg meat was used for the determination of microbiology and color difference. Unused samples were discarded to avoid secondary pollution.

1.2 Total Colony (TVC)

According to GB 4789.2-2016 "National Food Safety Standard for Determination of Total Bacterial Colonies in Food Microbiological Examination", the operation is performed, and the results are expressed in logarithmic log (CFU/g).

1.3 Coliform bacteria

According to GB 4789.3-2016 "National Food Safety Standard for Microbiological Examination of Coliform Bacteria in Food Safety", the total number of coliform bacteria is determined by the method, and the result is expressed in logarithmic MPN/100g.

1.4 Mold

According to GB 4789.15-2016 "National Food Safety Standard Food Microbiological Examination of Mold and Yeast Enumeration", the mold review method is operated, and the results are expressed in CFU/g.

1.5 acid value (AV)

Operate in accordance with the acid value determination method in GB/T 5009.37-2003 "Analysis Methods for Hygienic Standards of Edible Vegetable Oils".

1.6 peroxide value (POV)

Operate in accordance with the peroxide value determination method in GB/T 5538-2005 "Determination of Peroxide Value of Animal and Vegetable Fats and Fats".

1.7 Thiobarbituric acid reaction products (TBARS)

The determination of TBARS refers to the method of Fan et al. ^[1] , with appropriate changes. The specific operation is as follows: Weigh 5 g of ground sauce duck sample, add 45 mL of 7.5% trichloroacetic acid mixture, homogenate, and extract at 4° C. for 30 min. Centrifuge (6010×g, 10 min, 0° C.), filter. Take 5mL of 0.02mol/L TBA solution, mix well, and bathe in a 90°C water bath for 40min, cool to room temperature, and measure the absorbance value at a wavelength of 532nm. Each treatment was measured 3 times and the average value was taken.

1.8 Sensory evaluation

A scoring team composed of 10 food science teachers, postgraduates and undergraduates conducted sensory evaluation. The sensory evaluation indicators mainly include tissue state, color and smell. The indicators and scoring criteria of the sensory evaluation are shown in Table 1. The overall sensory score of the sample is the sum of the sensory scores of tissue state, color and smell.

Table 1 Sensory evaluation index of sauced duck

1.9 Establishment of Shelf Life Prediction Model

1.9.1 Zero-order chemical kinetic model

In this study, after analyzing the TBARS and mold of sauced duck, it belongs to the zero-order reaction model, and the formula of the zero-order reaction model is as follows:

B＝B ₀ -kt (1)

In the formula, B: quality index on day t of storage; B ₀ : initial value of quality index; t: product storage time; k: change rate constant of quality index.

1.9.2 Arrhenius equation

Chemical reaction kinetics describes the change of food quality over time. The reaction rate constant k is not only a function of food quality index but also a function of storage temperature T. Therefore, the sauced duck products are stored at 4°C, 25°C, and 37°C. , through the determination of two indicators of mold and TBARS during storage, the shelf life of sauced duck products under different storage temperature conditions can be predicted by using the Arrhenius equation ^[2] . The Arrhenius equation is a temperature-dependent model, and its reaction rate is related to the absolute temperature as follows:

k=k ₀ exp(–Ea/RT) (2)

In the formula, k is the reaction rate constant; Ea: activation energy of the reaction (empirical constant); T: absolute temperature (storage temperature); k ₀ : regression coefficient (empirical constant); R: gas constant 8.314J/(mol K ).

Combining the zero-order chemical reaction kinetic model and Arrhenius equation, the shelf life prediction model of sauced duck is obtained as follows:

In the formula, SL is the predicted shelf life, d; B ₀ is the initial value of the quality parameter, such as TBARS; B is the real-time quality factor; A ₀ is the pre-exponential (frequency) factor, that is, the reaction rate when the activation energy is zero; Ea is Activation energy, J/mol; R is gas constant, 8.3144J/(mol K); T is absolute temperature, K.

1.10 Data Analysis

Using Excel 2007 and SPSS 22.0 software to conduct correlation analysis on test data, using one-way analysis of variance, Tukey HSD method for significant difference analysis (p<0.05), using Origin 8.5 drawing software for drawing. The data are expressed as mean ± standard deviation, and the experiment was repeated three times.

2 Results and Discussion

2.1 Changes in quality indicators

2.1.1 Changes in the total bacterial count (TVC) of sauced duck during storage

The total number of bacterial colonies is an important indicator to measure the degree of food spoilage. When stored at different storage temperatures, the changes in the total bacterial count of the sauced duck are shown in Figure 2. Microorganisms are the main factor for the quality deterioration of meat products during storage. It can be seen from Figure 2 that the total number of bacterial colonies in sauced duck under various temperature conditions showed an overall upward trend, and the higher the storage temperature, the faster the total number of bacterial colonies in sauced duck increased. At 4, 25, and 37°C, the total number of bacterial colonies in sauced duck increased from the initial 4.28 log CFU/g to 5.85, 6.10, and 6.59 log CFU/g after 28 days of storage. The growth rate of the total number of colonies at 4°C was significantly lower than that at 25°C and 37°C (p<0.05). It shows that vacuum-packed sauced duck can be stored at low temperature to slow down the growth of microorganisms, which is beneficial to prolong the shelf life of sauced duck and ensure the quality of the product during the sales period.

2.1.2 Changes of Escherichia coli in sauced duck during storage

The number of coliform bacteria is one of the important indicators to evaluate the quality of food hygiene. It can be seen from Figure 3 that the initial number of coliform bacteria in sauced duck is 58MPN/100g, and as the storage time increases, the higher the temperature, the faster the growth rate. At the end of storage, the coliform bacteria in the 37°C experimental group was 6.67 times that of the 4°C experimental group, and there were significant differences among different experimental groups (p<0.05). It shows that temperature has a significant impact on the growth and reproduction of E. coli in sauced duck, and 4°C can better inhibit the growth of E. coli.

2.1.3 Changes of mold in sauced duck during storage

Mold is one of the important factors threatening the safety of cured poultry products. As shown in Figure 4, the initial value of the total number of molds in sauced duck was 142 CFU/g. With the increase of time, the mold in all experimental groups increased, and the 37°C experimental group increased the fastest (p<0.05). It may be that the water activity and temperature are suitable for mold growth. At the end of storage, the mold in the 37°C experimental group had reached 10176 CFU/g, which was 2.35 times that of the 4°C experimental group. At this point, the sauced duck was rotten and inedible, so it was determined that the total number of molds at 10,000 CFU/g was the end point of the sensory evaluation. It shows that low temperature can better inhibit the growth of mold, so that the sauced duck has better quality during the shelf life.

2.1.4 Changes in acid value (AV) of sauced duck during storage

Acid value is an index used to express the degree of rancidity of lipid hydrolysis ^[3] . The higher the acid value, the higher the free fatty acid content produced by lipid hydrolysis ^[4] . The experimental results are shown in Figure 5. Under three different storage temperature conditions, the initial AV value was 0.87mg/g, and the AV value showed an upward trend after 28 days of storage. The storage temperature had a significant impact on the acid value change during the storage of sauced duck. (p<0.05). During the storage process, the higher the temperature, the faster the AV value increased. The AV value of the sauced duck reached 3.04 mg/g at 37 °C, but only 1.61 mg/g at 4 °C, and at the end of storage There are significant differences (p<0.05) with other temperature storage groups. It shows that under the action of high temperature and oxygen, the oxidative degradation rate of lipids will be accelerated, and the acid value will rise significantly, resulting in the increase of free fatty acid content ^[5] .

2.1.5 Changes in peroxide value (POV) of sauced duck during storage

The peroxide value is an index to measure the primary oxidation products of fat, indicating the primary degree of fat oxidation ^[6] . Fatty acid hydroperoxide generated by fat oxidation reaction is the key product of fat oxidation and rancidity. Therefore, the degree of oxidative deterioration can be determined by measuring the level of fat peroxidation value. It can be seen from Figure 6 that the POV value of sauced duck under different storage temperatures is on the rise, and the initial value is 2.41g/100g (calculated as fat). After storage for 28 days, the POV values of sauced duck at 4, 25, and 37°C rose to 4.39, 5.67, and 7.11g/100g, respectively. During the whole storage process, the growth rate of POV was the fastest at 37°C, and there was a significant difference (p<0.05) with other experimental groups at the beginning of 7 days. This may be caused by two reasons. First, the rapid accumulation of some free fatty acids promotes the rapid oxidation of fat. Second, higher storage temperature reduces the activation energy of free fatty acid oxidation and promotes the oxidation of fat ^[7] . And the growth rate of POV value was the lowest under the storage condition of 4℃. This is roughly the same trend as the change of acid value of sauced duck under the same storage temperature. In summary, temperature has a significant effect on the peroxide value of sauced duck products during storage (p<0.05), and low temperature can effectively inhibit fat oxidation and prolong the shelf life of sauced duck.

2.1.6 Changes of thiobarbituric acid reaction products (TBARS) in sauced duck during storage

TBARS is an important index to evaluate the degree of fat oxidation and rancidity of meat, and it is one of the evaluation criteria for the quality of meat products during storage. The larger the TBARS, the higher the degree of fat oxidation, indicating that the higher the degree of fat oxidation and the worse the quality of the product ^{[8] ]} . It can be seen from Figure 7 that the initial TBARS value of the sample is 0.56mg/kg, and the growth rate is slow in the early storage period. The main reason is that the sauced duck is stored in vacuum packaging, which is isolated from the oxygen in the air, so it has a certain inhibitory effect on fat oxidation ^{[ 9]} . With the increase of storage time, there are significant differences in TBARS among different temperature condition groups (p<0.05), and the variation of TBARS under different temperature storage conditions is closely related to the storage temperature, the higher the temperature, the faster the change , low temperature will inhibit the oxidation of fat ^[10] . It has been reported that when the TBARS value is greater than 2.0mg/kg, the fat will be oxidized and produce an unpleasant smell ^[11] . In this experiment, only the 37°C experimental group reached 1.94mg/kg after storage for 28 days, which was close to the odor threshold of 2.0mg/kg, and the other experimental groups did not reach it. Therefore, in summary, storage temperature has a significant effect on TBARS (p<0.05). The higher the storage temperature, the more intense the oxidation of fat, which will increase the content of malondialdehyde (MAD), a derivative formed by oxidative degradation of saturated fatty acids in fat, and increase the content of malondialdehyde (MAD). TBARS growth.

2.1.6 Changes in sensory evaluation of sauced duck during storage

The shelf life of food is determined by sensory evaluation whether the product is acceptable or not. This method can accurately estimate the sensory shelf life of food ^[12,13] . See Figure 8 for the sensory evaluation results of sauced duck. Fresh sauced duck has an obvious characteristic aroma, the meat is firm without oil, and the appearance is sauce red. With the prolongation of the storage time, the color of the sauced duck gradually dimmed, the meat became loose and oily, and the characteristic aroma disappeared, and there was a rotten smell. There was no significant difference in the smell between 25°C and 37°C in the first seven days (p>0.05), indicating that the rotten duck in the 37°C experimental group was not obvious. It can be seen that the sensory scores of each experimental group decreased rapidly after 14 days, and the scores of the three indicators of appearance, color, smell, and tissue state in the 37°C storage experimental group decreased significantly compared with the other two groups (p<0.05). At the end of storage, the scores of the three indicators of appearance, color, smell, and tissue state in the 4°C experimental group were significantly higher than those in the other two temperature experimental groups (p<0.05). Therefore, the 4°C experimental group can better maintain the living state of the cells and inhibit the decomposition of proteins and fats in the body. To control the fading of sauced duck meat, the combination of 4°C and vacuum packaging can significantly improve the sensory quality of sauced duck and delay its decline.

2.2 Kinetic model establishment

2.2.1 Correlation between physical and chemical indicators and sensory scores of sauced duck during storage

Table 2 Pearson correlation coefficient table between physical and chemical indicators and overall sensory score of sauced duck during storage

Note: **The significance level is below 0.01, that is, the possibility of no significant correlation is less than or equal to 0.01

During the storage of sauced duck samples, the correlation between each physical and chemical index and sensory score is shown in Table 2. The larger the Pearson correlation coefficient, the greater the correlation between the two. It can be seen from Table 2 that the Pearson correlation coefficients between the sensory scores of sauced duck products at different storage temperatures and most of the physical and chemical indicators are greater than 0.9, indicating that the indicators The correlation between them is better. And the sensory scores of sauced duck products under different storage temperatures were significantly negatively correlated with each physical and chemical index (p<0.05), and there was a significant positive correlation between each physical and chemical index (p<0.05). Among all relevant detection indicators, the correlation between the total number of molds, TBARS and sensory scores has a very significant relationship (4°C: 0.974, 0.992; 25°C: 0.961, 0.995; 37°C: 0.996, 0.985), so the mold and TBARS as the key factors of the quality change and shelf life dynamics prediction model of sauced duck. According to the above analysis, with the continuous increase of mold and TBARS, the sensory score gradually decreased, and the correlation between the three was very high; at the same time, the lower the storage temperature, the higher the correlation among the three, showing a negative correlation change. This also shows that this experiment uses the high temperature accelerated test to speculate that the low temperature storage period has high reliability; during the storage at three storage temperatures, when the total number of molds is greater than 10000CFU/g or the TBARS value is greater than 2mg/kg, the sensory score of the sample is the lowest , so it can be considered that when the total number of molds is 10000CFU/g or the TBARS value is greater than 2mg/mg, the shelf life of sauced duck products has reached the end.

2.2.2 Kinetic analysis of quality change

In the process of food processing and storage, the quality change of most foods conforms to the zero-order or first-order reaction mode ^[14] . In this study, referring to the quality change parameters of sauced duck, SPSS 22.0 was used to perform linear fitting on it, and the zero-order response model was obtained. and first-order rate constants and coefficients of determination thereof, specifically see Table 3, R ² is larger and shows that the overall linear relationship is better, as can be seen from Table 3, the coefficients of determination of the zero-order and first-order regression equations under different storage temperatures are all greater than 0.9, indicating that The better the fitting accuracy. In addition, the size of ∑R ² can also help to determine the level of food quality change. The correlation coefficient ∑R ² of the zero-order kinetic regression of TBARS is larger than that of the first-order kinetic regression, while the zero-order kinetic regression of mold The correlation coefficient ∑R ² is also larger than that of the first-order kinetics, and a larger ∑R ² indicates a higher fitting accuracy ^[15] . Comprehensive analysis showed that the changing rules of TBARS index and mold index of sauced duck conformed to the zero-order chemical reaction kinetic model.

Table 3 Kinetic model parameters of quality change of sauced duck under different storage temperatures

2.2.3 The establishment of the shelf life prediction model of TBARS and mold in sauced duck during storage

The data of TBARS and mold were processed by SPSS 22.0 software to obtain regression equations and change rate constants k of different indicators at different temperatures. The results are shown in Table 4.

Table 4 Regression equations of TBARS and mold at different temperatures

It can be seen from Table 4 that with the prolongation of storage time, TBARS and mold continue to increase, and there is a linear relationship with storage time, and ^the multiple correlation coefficient R of the regression equation is greater than 0.95, indicating that the regression equation can better reflect TBARS, The relationship between mold and storage conditions proves that the two indicators are the key factors reflecting the quality change of sauced duck, and also shows that the quality change of sauced duck during storage can be simulated by this kinetic model.

The linear regression equation obtained by plotting lnk and 1/T(×1000) is shown in Table 5

Table 5 Equations corresponding to TBARS and mold

Calculated from the linear equation in Table 5 above, the activation energy Ea corresponding to TBARS and mold is 25809.98kJ/mol and 16034.13kJ/mol, respectively, and the pre-exponential factor _k0 is 1072.32 and 165097.25, respectively. The R ² values of the Arrhenius equation curves of TBARS and mold changes of sauced duck products under different storage temperature conditions were all greater than 0.96, indicating that the fitting degree of the linear equation reached a significant level. Through calculation and equation (3), the shelf life prediction model of TBARS and mold of sauced duck was obtained.

According to the TBARS and mold shelf life prediction equation obtained above, when the storage temperature, initial value and end point value are determined, the storage time of sauced duck under a certain temperature condition can be calculated, and its shelf life can be predicted. In addition, the TBARS or mold after storage for a certain period of time at a certain storage temperature can also be calculated through the storage temperature, initial value and storage time of the sauced duck, and the change of its quality can be monitored.

2.3 Validation and shelf life prediction of sauced duck shelf life prediction model

According to the results of sensory evaluation, TBARS value exceeding 2.0mg/kg or the total number of molds exceeding 10000CFU/g are regarded as the end of shelf life, and the shelf life prediction model of sauced duck under storage temperature of 4-37℃ is used to predict the shelf life . Table 6 shows the comparison of the measured and predicted values of TBARS and the total number of molds for the shelf life of sauced duck under storage conditions of 4, 25, and 37°C.

Table 6 The shelf life prediction value of each index under different storage temperatures

It can be seen from Table 6 that the accuracy rate of the predicted value of the predicted value of the sauced duck shelf life prediction model established in this study is basically about ±10%. It shows that this shelf life prediction model can effectively predict the quality and remaining shelf life of sauced duck products under different storage temperature conditions. The verification results show that the prediction model established by using TBARS as the characteristic index of sauced duck products under different storage temperature conditions has high accuracy. Therefore, some theoretical guidance can be provided for the safe storage of sauced duck pickled products.

3 Conclusion

In this experiment, the changes of sensory, physical and chemical and microbial characteristics of sauced duck were studied under different temperature conditions of 4, 25 and 37°C, and a corresponding prediction kinetic model was established. The specific conclusions are: with the extension of storage time, the three The sensory scores of sauced ducks stored at different temperatures gradually decreased, while the total number of bacteria, coliforms, mold, peroxide value, acid value, and thiobarbituric acid value were in contrast. The low temperature condition of 4℃ is the most favorable for the storage of sauced duck, and it can inhibit the reproduction of microorganisms, fatty acid spoilage and oxidation, and has a significant difference compared with the other two temperature conditions (p<0.05). Correlation analysis showed that the Pearson correlation coefficients between the sensory scores of sauced duck and most of the physical and chemical indicators under different storage temperatures were greater than 0.9, and the correlation coefficients between TBARS and mold were larger than other indicators at different temperatures. Mold is an indicator of the shelf life prediction model. At the same time, after fitting the two indicators with the zero-order and first-order chemical kinetic models under different storage temperature conditions, it was found that the fitting accuracy of the zero-order kinetic model was higher, and R2 was greater than 0.9. Therefore, the zero-order kinetic model and the Arrhenius equation are used to establish the prediction model as

and

The results of model verification show that the relative error between the theoretical prediction value and the actual value is about 10%, indicating that the model is reliable. Therefore, the prediction model established according to the two indicators of TBARS and mold during the storage period of sauced duck can better predict the shelf life of sauced duck under the temperature condition of 4-37 ℃, and can provide a basis for predicting and controlling the storage period of sauced duck. Provide a realistic reference for shelf life prediction.

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Claims (6)

1. A method for predicting the shelf life of sauced duck is characterized in that: research is carried out on mold and thiobarbituric acid reaction product of sauced duck under different temperature storage conditions, and establishment of mold and thiobarbituric acid reaction product Regarding the kinetic model of time and temperature, and established the shelf life prediction model of sauced duck with the reaction product of mold and thiobarbituric acid, the steps are as follows: 1) Put the repurchased sauced duck into vacuum packaging bags on the aseptic operation table; 2) The packaged sauced ducks were randomly divided into three groups, stored at 4, 25, and 37°C, and samples were taken at certain time intervals to determine the reaction products of mold and thiobarbituric acid; 3) According to the change rule of mold and thiobarbituric acid reaction product with time, establish a kinetic model of mold and thiobarbituric acid reaction product changing with temperature; 4) Use the Arrhenius equation to analyze the temperature T and the reaction rate constant k to obtain the pre-exponential factor A ₀ and the reaction activation energy Ea; 5) The binding kinetic model was established to predict the shelf life based on the reaction product of mold and thiobarbituric acid at 4-37°C: In the formula, SL is the remaining shelf life, d; B ₀ is the initial value of mold or thiobarbituric acid reaction product; B is the measured value of mold or thiobarbituric acid reaction product at a certain time; A ₀ is the index before Factor; Ea is the activation energy, J/mol; R is the gas constant, 8.3144J/(mol K); T is the absolute temperature, K; 6) Validation and selection of shelf life prediction models. 2. the method for predicting the shelf life of sauced duck as claimed in claim 1 is characterized in that: the design sampling time interval is to get a sample every 7 days. 3. The method for predicting the shelf life of sauced duck as claimed in claim 1 is characterized in that: in combination with the national standard, after comprehensively considering the sensory evaluation of sauced duck, it is determined that the total number of molds at the end of the sauced duck's shelf life is 10000CFU/g, and sulfo The barbituric acid reaction product was 2.0 mg/kg. 4. the method for predicting the shelf life of sauced duck as claimed in claim 1 is characterized in that: adopt zero-order kinetics model and first-order kinetics model to mold and thiobarbituric acid reaction product of sauced duck under different temperatures Regression analysis was carried out, and the regression coefficient R ² was compared to determine that the quality change of sauced duck was a zero-order kinetic model. 5. the method for predicting the shelf life of sauced duck as claimed in claim 1, is characterized in that: under different temperatures, rate response constant k is carried out curve fitting and obtains the change activation energy of sauce duck mold and thiobarbituric acid reaction product The Ea are 16034.13 and 25809.98kJ/mol, respectively, and the pre-exponential factor k ₀ are 165097.25 and 1072.32, respectively. 6. predict the model of sauced duck shelf life as claimed in claim 5, it is characterized in that: Mold-based shelf-life prediction model: Predictive models based on TBARS values: SL _(Mould) and SL _(TBARS) are the remaining shelf life of the sauced duck mold and thiobarbituric acid reaction product models, respectively, d.