Insight

          The shelf life, the same as the shelf life, is the period of time during which the food retains its characteristic properties under proper storage conditions.
          Not only the food producer is responsible for the expiration date, but also anyone in the food chain, including the consumer himself, who must properly store and consume the product.
          The following information is placed on the food label: "It is better to use until ...", after which, under proper storage conditions, the food retains its characteristic quality indicators (eg: canned, dry and frozen food) from a microbiological point of view, perishable food, which may pose a danger For consumer health, a  "use by..." deadline should be posted. After the expiration of the minimum shelf life, the food must not be placed on the market.
          There are internal and external factors affecting the quality of food products.
          Internal factors that cannot be controlled during food storage, for example: Ph, moisture content, water activity, nutrient content, antimicrobial agents, biological structure and oxidation-reduction reactions.
          Ph shows how acidic or alkaline a food is. The lower the Ph (less than 7), the more acidic the food is, and the reproduction of microorganisms is more inhibited. Most foods are acidic, but foods such as red meat, chicken, fish, eggs, and vegetables have an optimal pH (6.6-7.5) for microbial growth.
          Moisture content shows the amount of water in the food, and active water - the water available for microorganisms. The higher the water activity, the faster the microorganisms multiply. Dehydration of food is often used to reduce the amount of active water. Food, for example, jam, has a high moisture content, and the active water replacement is low, due to the fact that the sugar in the jam binds water and therefore reduces the amount of active water. In addition, the more active water in the food, the more intense the Maillard reaction, which affects the taste, color and texture of the food.
         In general, when creating a new product, it is possible to extend the shelf life of food by active water manipulation, since water management is a decisive factor in terms of both food safety and quality indicators. The manufacturer of the product may change the amount of active water by using different technological processes: time, temperature, air humidity controller, additives.
         Oxidation of fats, which leads to deterioration of taste, color and aroma of food, is also essential for shelf life and food quality. It is because of this chemical reaction that nuts and some snacks have a tangy taste. The presence of oxygen is a necessary condition for oxidative stress, and light and temperature can accelerate the above-mentioned reaction.
         Another contributing factor to product spoilage is the presence of nutrients. The richer the food in nutrients, the greater the chance of its microbial contamination, since nutrients are nutrients for microbes. Products such as red meat, chicken, eggs, and seafood are rich in protein and, therefore, are an ideal breeding ground for bacteria.
         Some foods, such as eggs, garlic, blueberries, have innate defense mechanisms - antimicrobial agents that are distributed naturally. For example, eggs contain the enzyme lysozyme, which prevents the growth of gram-positive bacteria.
         As for the biological structure. This refers to the outer covering of the food, such as the skin in the case of animals, the shell in the case of eggs and nuts. Both of them have a protective function and protect the product from infestation.
         As mentioned, in addition to internal factors, shelf life is affected by external factors that can be controlled. Such factors are: temperature, time, relative air humidity, presence of gases, physical stress and others.
         Temperature is the most important factor that must be controlled to avoid contamination. For this purpose, the product can be stored both cold and hot. It should be noted here that there are microorganisms that can grow and develop in extreme temperature conditions, although in general the most optimal temperature range for bacteria is 21-38°C. Temperature is also important in manipulating the rate of some chemical reactions.
         Time and temperature are often grouped together, since the interaction of these two factors leads to the destruction of microorganisms. It should be noted that a necessary stage in the production of some products to obtain the desired quality is a delay in time, for example in the case of wine, cheese and any fermented product, at which time it is very important to create and control the proper conditions, since pollution occurs parallel to the progress of time.
         In the case of food, relative humidity affects water activity, so this factor is very important, because it is the reduction of water activity that leads to the prevention of contamination.
         For products such as chips, fruit and meat, pressurization with some inert gas may be an effective way to extend their shelf life. Vacuum packaging is the best example of this.
          Physical stress may have a negative effect on the quality of the product, such as bruising, deformation or other physical effects, so it is important to pack the product in time and properly.
          There are 4 categories of tests to determine the expiration date:
          Sensory analysis will be carried out by a competent panelist guided by a predetermined method known to him.
           A microbiological test is used to check quality and safety. Environmental factors such as temperature and humidity during storage should be considered when planning tests. This will help the team determine which microorganisms will need to be tested. First, the organisms expected to grow in the food should be tested. For example, if the environment is not anaerobic, it will not be necessary to test for anaerobic bacteria either.
            It is used to make changes in product quality. Chemical Tests - Testing of Ph, Free Fatty Acids and Total Volatile Nitrogen. In order to avoid chemical contamination, it is possible to check the quality of raw materials upon receipt, reduce exposure time, use additives, and select suitable packaging material.
            The physical test includes checking the product's texture, color, packaging, and the so-called "travel test," which helps identify hazards during transportation and storage. Deterioration of physical quality may be reduced by using some technological processes, such as blanching of fruits and vegetables before freezing, which results in inactivation of the enzyme responsible for browning.
             It is worth noting that the shelf life of the product should be shorter than it reaches a noticeable deterioration in quality, based on the fact that the manufacturer takes appropriate measures for the disposal of non-conforming products.
             There are 2 methods of determining the expiration date: direct and indirect
             In direct time, the product's shelf life is determined by the environment in which it is stored. This test can be used for any type of food and its advantage is that there is no need to perform any calculations, because we can directly see the result of a specific condition. The disadvantage of the test is that it takes a long time to obtain a noticeable change, which is time-consuming, and is only adapted to uniform, simulated environmental conditions.
             The indirect method is the most common simulated fit test. It is an accelerated method in which the product is placed under controlled environmental conditions where factors are maintained at a higher level than under normal conditions. This type of test is used with products that have a long shelf life.
             The indirect test also includes predictive modeling of determination, during which, through appropriate calculations, it is possible to predict the growth of bacteria in an environment with certain conditions.