At present, the domestic provincial CDC does this:
Put the product in a constant temperature and humidity incubator, and measure the quality and hygiene indicators once a month. If the index is stable for three months, the shelf life of the product can be set at three years.
Culture conditions: the temperature is about 37℃ and the humidity is about 75%.
Of course, if your product quality and hygiene indicators are not ideal, you can shorten the testing period appropriately. You can calculate the shelf life of the corresponding products.
In the experiment of beverage shelf life, three temperatures are generally set, that is, the samples are stored in three incubators at 5℃, 25℃ and 37℃ respectively. Samples at 5℃ are used as standard samples or control samples, samples at 25℃ are used as simulated shelves, and samples at 37℃ are used as environmentally destructive samples. Evaluate the samples at 37 degrees every 5 days or so and compare them with the samples at 5 degrees. When the difference between the 37-degree sample and the 5-degree sample is significant or unacceptable, the experiment of the 37-degree sample is stopped, and the time obtained by multiplying the storage time of the sample at 37 degrees by 3 is the approximate shelf life of the product. The sample continued the experiment at 25 degrees. When the sample under the condition of 25 degrees is unacceptable compared with the sample under the condition of 5 degrees, the experiment under the condition of 25 degrees also stops, and the storage period is regarded as the actual shelf life of the product.
The shelf life inspection of beverages should be divided into three parts: microorganism, appearance and taste, and experiments were designed to compare them. Microbial prediction is simple; Appearance is mainly to find the problems of discoloration, precipitation and stratification. Testers should first predict the most likely problems according to product formula, technology and experience, such as yellowing of colorless drinks, fading of colored drinks and aggravation of milk precipitation stratification, predict precipitation stratification with 37℃ and refrigerated samples, and predict discoloration with 50℃ and refrigerated samples. Taste should be divided into citrus flavor, light flavor or rich flavor, and predicted by simulating the market sales environment.
This is mainly to provide an idea and method. The method is similar, but the application needs specific product analysis.
Accelerated tests (that is, destructive tests) are generally done, which are directly related to temperature and time. For example, the 37-degree heat preservation test in yogurt for one week proves that it can last for half a month in the market. Paper towels can be stored at 54℃ for half a month for one year and at 37℃ for one month.
I know there is a method of experimental mathematics, which can make the number of experiments get the best results at the least cost; That is, optimization method (also known as golden section method); Or 0.6 18 method; This method is the most basic and simple way to do experiments; In fact, this method is often used in securities analysis! As early as the sixties and seventies, mathematician Hua put forward this concept, and it was widely used at that time.
Specifically, when you are doing various tests, for example, suppose that when you are doing a 37-degree fresh-keeping test of yogurt, it has deteriorated after a month of heat preservation; At this time, you can use 0.6 18 days for 30 times, that is, 18.5 days, and do this experiment again; If the results still deteriorate, the experiment will continue to be multiplied by 0.6 18.5 days 18, which is about110.5 days. If it hasn't deteriorated in 18.5 days, you can use the number after 30 days to subtract 18.5 days times 0.6 18 days plus 18.5 days, and do this experiment in about 25 days, and so on. You can get the best experimental data with the least number of experiments, so as to determine the actual preservation data of your food;
This experimental method can also be used for the study of food formula; 1998, I used this method to help a friend experiment the formula of "quarrying dry tea"; Only six experiments were done, and the best formula data was obtained with less than 60 kg of soybean (or at least 10 kg at a time because of the large refiner); Compared with dry tea in the market, the toughness and taste of dry tea are greatly improved;
Accelerated test of food storage period and its application
By using the principle of chemical kinetics, the storage environment is changed and the storage period of food is shortened, so that the storage period of longevity food (more than one year) can be obtained in a short time, and it can be used to test the stability of food to ensure the commercial storage period of food.
A. Basic principles
The principle of accelerated food storage test is to quantify the influence of external factors such as temperature, humidity, air pressure and light on deterioration reaction by chemical kinetics. By controlling the food in an environment where one or more external factors are higher than the normal level, the speed of deterioration can be accelerated or accelerated, and it can be judged whether the product has deteriorated in a shorter time than normal. Because the external factors affecting deterioration can be quantified and the degree of acceleration can be calculated, the actual storage period of the product under normal storage conditions can be calculated.
Because many packaged foods can usually be stored for more than one year, it is expected that the storage period will last as long as possible to the required time (commercial storage period) by evaluating the external factors that affect the storage period, such as the change of product composition (using new antioxidants or thickeners), the change of processing technology (using different disinfection time or temperature), or the change of packaging materials (using new polymer films). However, many companies can't wait for such a long time to know whether these new products/processes/new packaging materials can provide sufficient storage period, because this will affect other decisions (such as contracts for new factories, purchasing new equipment or arranging the supply of new packaging materials, etc.). ). Therefore, some methods are needed to speed up the detection of product shelf life, and accelerated detection of food shelf life (ASLT) came into being. Similar methods have been widely used in the pharmaceutical industry for a long time to test the shelf life and efficacy.
2 Determination of shelf life of food
Under given conditions, the decline of product quality is inversely proportional to time. The ratio of storage period at any two temperatures with temperature difference of10 c = storage period at temperature t/storage period at temperature (t+10 c) has great influence on storage period:
Effect of Q 10 on storage period
Storage period (weeks)
Temperature cq10 = 2q10 = 2.5q10 = 3q10 = 5.
50 2* 2* 2* 2*
40 4 5 6 10
30 8 12.5 18 50
20 16 3 1.3 54 4.8 years
* The storage period at 50 C is assumed to be 2 weeks.
Generally speaking, the Q 10 of canned food is 1. 1~4, and the q 1.5 ~ 10 of dehydrated products. 3-40 parts of frozen products.
B. accelerated food storage test (ASLT) steps
The following steps can be used to set the shelf life of food:
C, determining the microbial safety and quality index of the product;
D. Select key deterioration reactions, which will lead to the deterioration of product quality and make it unacceptable to consumers, and decide which tests must be carried out when testing products (senses or instruments);
E. Selection of packaging materials: A series of packaging materials are tested, so as to select the most cost-effective material (that is, it is economical and meets a certain storage period).
F. Select the external factors that will be used to accelerate the reaction, see the suggested temperature in the table below, and at least two must be selected.
ASLT recommended storage conditions
Frozen food, dehydrated food, canned food
-40℃ 0℃ 5℃-15℃ 23℃ (room temperature)
23 degrees Celsius (room temperature)-10 degrees Celsius 30 degrees Celsius 30 degrees Celsius -5 degrees Celsius
40 degrees Celsius, 35 degrees Celsius, 45 degrees Celsius, 40 degrees Celsius
R Record the storage time of the product at the test temperature using the coordinate curve. If the value of Q 10 is unknown, a comprehensive ASLT test must be carried out.
South to determine the number of tests
f2=f 1 Q 10？ 6? 2/ 10
F 1: test time at higher test temperature T 1 (days, weeks).
F2: Test time at lower test temperature T2 (days, weeks)
6? Temperature difference between 2:t 1 and T2
Because if a product is tested at 40℃ for one month, then at 30℃, Q 10=3, the product needs to be tested at least.
F2 =1x 3 (10/10) = 3 months.
If Q 10 is unknown, it's best to carry out multiple tests, and at least 6 data points are needed to minimize the error, otherwise the reliability of the obtained storage period will decrease.
The unit calculates the number of samples stored under each test condition.
Verb (abbreviation of verb) starts ASLT, draws the obtained data on the coordinate map, and increases or decreases the sampling times as needed.
W. Evaluate the K value or storage period from each test storage condition and establish a storage period map appropriately, and estimate the storage period under normal conditions accordingly.
C. Practical application examples
Because our company's products are mainly dehydrated soup, we choose two storage conditions: 30 C/75% relative humidity and 37 C/75% relative humidity.
-The sensory test method conforms to the international standard method of ISO3972.
-Constant temperature and humidity device: VC0057 constant temperature and humidity box made in Germany can be used to adjust the required temperature and humidity; Or take out the desiccant from the glass drying tray, put it into the saturated solution of sodium chloride, and then put it into the incubator with the temperature of 30℃ and 37℃ respectively, and the required constant temperature and humidity device can also be obtained.
6? 1 colorless and odorless drinking water.
6? 1 electric or gas stove.
6? 1 questionnaire for testers to answer.
6? 1 Independent, sound insulation test area, white fluorescent lamp.
6? 1 standard sample (soup products, seasoning products ...)
6? 1 plates, glasses and spoons.
Put the sample into a constant temperature and humidity device and evaluate it every 1.5~3 months (the time interval depends on the product type and storage conditions), and compare it with the standard sample.
The evaluation results are scored as follows:
5,-All the characteristics of the product are completely consistent with the standard sample.
4,5 products are acceptable, but slightly different from the standard samples.
4,-The product is qualified, but there are some differences compared with the standard sample.
3. 5 The product is qualified, but it is obviously different from the standard sample.
3.- The product is neither acceptable nor acceptable.
2,5 The product is slightly unacceptable.
2.- The product is a bit unacceptable.
The product of 1 5 is obviously unacceptable.
1,-The product is totally unacceptable
The obtained results are averaged.
A score of 3 is an acceptable critical point. If this score is reached, it means that the product has reached the storage period.
As a general standard, if dehydrated products (soup and seasoning) are stored at 37 ℃/ 75% relative humidity and 30 ℃/ 75% relative humidity for 3 months and 12 months respectively, and still get a score of not less than 3, the products can be regarded as qualified.
According to this principle, the shelf life of dehydrated soup under standard storage conditions can be estimated according to the coordinate diagram composed of the following ASLT data:
Temperature t c storage period LogSL
T 1 LogSL 1
T2 log 12
T3 log 13
Standard Storage Temperature StdT (℃) Standard Storage Period Log (Std SL)
D. Stability test
Similarly, this method can also be used to test the stability of products to ensure the commercial shelf life of products.
The methods and instruments used are the same as above, but the coordinates drawn are different. Taking chicken powder as an example, detailed inspection, evaluation and analysis were carried out, and the conclusion was that the commercial shelf life of the product was set at 24 months.