How to extend the shelf life of food? During storage, food is easily attacked by microorganisms and spoils. There are many factors that cause food spoilage, mainly chemical factors, biochemical factors and microbial factors, among which microorganisms play a leading role. In order to prolong the shelf life of food, it is necessary to kill microorganisms or inhibit their growth and reproduction. Therefore, we can extend the shelf life of food from the following aspects. 1, with proper heat treatment or low temperature treatment. Temperature is one of the most important factors affecting the growth and survival of microorganisms. Any microorganism has its optimum temperature range, and the growth of microorganisms above or below this range will be inhibited. The vegetative cells and viruses of most bacteria, yeasts and molds can be killed at 50 ~ 60℃ for 65438±00min. Some of them are more sensitive, while others are the opposite. Therefore, high temperature treatment can be used to kill microorganisms by heating to prolong the shelf life of food. When the temperature is lower than 0℃, the water in microorganisms freezes, biochemical reactions cannot be carried out, and some even die, so it is also a common method to preserve food at low temperature. 2. Adjust the pH value of the system. The pH value of the system has a great influence on the life activities of microorganisms, and each microorganism has its optimum pH value and a certain pH range. The optimum pH of most bacteria is 6.5-7.5, that of actinomycetes is 7.5-8.0, and that of yeast and mold is 5.0-6.0. Below pH4.3, bacteria basically have no reproductive ability except yeast and mold. Therefore, lowering the pH value of the system is one of the methods to prolong the shelf life of food without affecting the taste. 3. Reduce the water activity of the system. Food corruption is related to the water content in food, but the degree of corruption is not proportional to the water content, and the size of water activity can better explain the problem of food corruption. The greater the water activity, the more free water content in food, and the easier it is to be infected by microorganisms; The smaller the water activity in food, the more stable the food, and the less the problem of spoilage. Therefore, reducing water activity is one of the means to prolong the shelf life of food. One of the commonly used methods is drying, which has low water content and low water activity. Another common method is pickling with sugar and salt. Sucrose and salt are hydrophilic substances, which are easy to combine with water, making free water into bound water, and the activity of water is also reduced. 4. Reduce the oxygen content of the system. The proliferation of microorganisms requires different gas environments. In aerobic environment, mold, yeast and bacteria can cause food deterioration, while in anoxic environment, only yeast and bacteria can cause deterioration. High concentrations of CO2 and N2 will inhibit the growth of microorganisms. Therefore, vacuum packaging or vacuum nitrogen-filled packaging can be used to extend the shelf life of food. 5. Improve the osmotic pressure of the system. The cell membrane of microorganism belongs to semi-permeable membrane. When microbial cells are placed in a high-permeability environment, water will enter the solution around the cells from low-concentration cells through the cell membrane, resulting in dehydration of the cells and separation of the plasma wall, making the cells unable to grow or even die. Therefore, high concentrations of salt and sugar are usually used to store food. The concentration of sugar is usually 50-70%, and the concentration of salt is 10- 15%. 6. Carry out proper electromagnetic wave treatment on food. Electromagnetic waves of certain wavelengths, such as X-rays, microwaves, ultraviolet rays and radioisotope rays, have the ability to kill microorganisms. Although this application has not been fully developed, it has been applied to some foods and is also a way to extend the shelf life of food. 7. Add appropriate preservatives. Adding food preservatives is one of the effective means to delay food deterioration. Preservatives are generally divided into chemical synthetic products and natural products, among which chemical synthetic products are divided into acids, esters and inorganic preservatives, which are widely used in practical production. Natural products include plant sources, animal sources, microbial sources, mineral preservatives and some natural organic substances. & lt/FONT & gt； & lt/SPAN>。
How to extend the shelf life of food? The expiration of food is mainly caused by microorganisms, so there are several ways to extend the shelf life of food:
Control the initial microbial population:
Can be sterilized by heating, ultraviolet rays and other methods to reduce or kill microorganisms in food;
Prevent the reproduction of microorganisms in food;
Control by destroying the conditions required for microbial reproduction, such as:
Temperature: low-temperature storage and transportation can prevent microbial reproduction and extend the validity period;
Oxygen: for itchy microorganisms, vacuum packaging can effectively inhibit their growth;
Moisture: Reducing food moisture (especially water activity) can inhibit microorganisms;
Osmotic pressure: high salt and high sugar environment can inhibit microorganisms;
Preservatives: chemical methods can be used, and the validity period can be extended by adding appropriate preservatives allowed by the state.
Whether the shelf life of food can ensure the quality of food depends on whether the environmental conditions of food in circulation meet the storage conditions of products. If there is, it is generally no problem, but it is not absolute. (Sometimes the products are not strictly implemented according to the requirements during processing, such as poor hygiene, incomplete sterilization, lax sealing, etc. This will lead to premature deterioration. )
What does the shelf life of food mean? Scientific research and practice have proved that liquor, honey, vinegar and salt are all non-perishable foods.
Liquor:
Liquor with an alcohol content of more than 10%, that is, liquor with an alcohol content of more than 10 degrees, has its own disinfection function. Under sealed conditions, microorganisms are not easy to invade and reproduce, so they will never deteriorate. However, this does not mean that the longer the wine is stored, the better. After five years, the taste of ordinary-flavor liquor will become weak and the flavor will weaken. Maotai-flavor aged wine is good wine, but whether Luzhou-flavor wine stored for many years is good wine is still inconclusive.
Dear:
Fresh and mature honey is a transparent or translucent colloidal viscous liquid, with sugar accounting for more than 3/4 of the total honey and low water content, so bacteria and yeast can't survive in honey. In addition, honey also contains 0. 1% -0.4% bacteriostatic agent. Therefore, mature honey is not easy to deteriorate after long-term storage. However, if it is not the mature honey or inferior products mixed with water, it will be fermented and foamed after a period of time, becoming sour and inedible.
Vinegar:
Vinegar has antibacterial and bactericidal effects, and can be used for food preservation and antisepsis, such as acid soaking. The storage period of vinegar is relatively long, but it is also affected by technology and raw materials. Mature vinegar is brewed with better technology, sealed in a jar and placed underground. The longer the year, the more mellow the taste.
Salt:
The main component of salt is sodium chloride, and its chemical properties are very stable. Like sugar, edible salt is usually used to store food and is a natural preservative. However, if the iodized salt we often eat is kept away from light and high temperature for too long, the iodine content will decrease, but the quality of the salt will not change.
Precautions:
Solid sugar includes commonly used white sugar, soft sugar, rock sugar and single crystal rock sugar. Solid sugar has low water content and strong osmotic pressure, which is not conducive to microbial growth and is not easy to be polluted. Sugar is also often used to store food, such as candied fruit and preserved fruit. However, sugar absorbs water easily. If it is improperly placed, its properties will change and it will be contaminated by microorganisms.
Can copper powder be used to extend the shelf life of food? Why thirty days? Nitrogen: The chemical formula is N2, which is usually a colorless and odorless gas. Usually, the density of nitrogen is less than that of air. Nitrogen accounts for 78. 12% (volume fraction) of the total atmospheric volume and is the main component of air. At standard atmospheric pressure, when cooled to-195.8℃, it becomes a colorless liquid, and when cooled to -209.8℃, liquid nitrogen becomes a snow-like solid. Nitrogen is chemically inactive, so it is difficult to react with other substances at room temperature, but it can chemically change with some substances at high temperature and high energy, thus making new substances useful to human beings. Although nitrogen is more than oxygen in the atmosphere, people don't know nitrogen before they know oxygen because of its inactive nature. But it was discovered before oxygen appeared. Shortly after British chemist Black (J. 1728- 1799) discovered carbonic acid gas in 1775, he found that a large amount of air remained in carbonic acid gas produced by burning charcoal in a glass cover, even after it was absorbed by caustic potash solution. Later, his student D. Rutherford continued to experiment with animals, put the mouse in a closed glass cover until it died, and found that the air volume in the glass cover decreased110; If the residual gas is absorbed by caustic potash solution, it will continue to decrease the volume of111. D. Rutherford found that mice can't live in the air and burn candles, but they can still see the faint candlelight; After the candle is extinguished, put a small amount of phosphorus, which can still burn for a while, which is beneficial to remove the auxiliary gas in the air. By studying the residual gas after phosphorus combustion, D. Rutherford found that this gas can not sustain life, has fire extinguishing performance, and is insoluble in caustic potash, so it was named as "polluted gas" or "toxic gas". In the same year, priestley made a similar combustion experiment and found that 1/5 air was converted into carbonic acid gas, and the gas absorbed by lime water was not helpful for combustion or breathing. Because both he and D. Rutherford believed in phlogiston theory, they called the remaining gas "air saturated with phlogiston".
Excel reminds food shelf life. I want to remind food shelf life with Excel. Just enter the production date and shelf life, and the remaining assumption A will be displayed as the production date.
B is listed as shelf life days.
Column c can enter the formula = b1-(today ()-a1+1).
How to prolong the shelf life of vacuum-packed food and put some desiccant in it. If the product is kept in vacuum and the desiccant is preserved, there will be no bacterial growth, which will prolong the shelf life.
Food expiration date reminder is a very practical gadget, and the interface looks quite comfortable. At first, I was worried that it was inconvenient to use all English, but later I found that it was ok to input Chinese with other words. It is also very convenient to manage and can be automatically screened. What has expired and what is about to expire is clear at a glance. As long as you watch it regularly, you won't waste food, and the effect is really good.