Outline of mould proof and fresh-keeping technolog

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Summary of food anti mildew and fresh-keeping technology

1. the main factors causing food spoilage

(1) biological factors

(a) microorganisms

the main factors affecting the growth and development of microorganisms are water activity, pH value, oxygen, nutrients Temperature

(b) pests and rodents

(2) chemical factors

(a) enzymatic action

(b) non enzymatic action (non enzymatic Browning)

(c) oxidation

(3) physical factors

(a) temperature

(b) water activity

(c) light

(4) other factors

2 basic principles of food preservation

(1) microbial control

(a) heating/cooling

(b) control of water activity

(c) Control moisture state - vitrification storage theory

(d) control pH value

(E) control osmotic pressure

(f) smoke

(g) change gas composition

(H) use additives

(I) irradiation

(J) microbial fermentation

Ian Fuller, vice president of business development and engineering of the company, talked to reinforced plastics about (2) control of enzymes and other factors

3. Fence technology

food processing, storage In the process of transportation, sales and consumption, a large number of corruption and deterioration are often caused by the pollution of the installation and commissioning of micro static steel testing machine. For a long time, in order to control the growth and development of microorganisms, reduce the losses caused by food spoilage, and ensure the preservation, health and safety of food, people have adopted many physical, chemical and biological technical measures in food preservation, such as low-temperature preservation, dehydration preservation, canning, pickling preservation, concentration preservation, chemical preservation, fermentation preservation, irradiation preservation, etc. These technologies have been widely and successfully applied in food processing and preservation

The application of fence technology in food preservation was proposed by leistner (1976) of the German meat research center. He attributed the methods or principles of food preservation to the effects of factors such as high temperature treatment (f), low temperature refrigeration (T), reduction of water activity (AW), acidification (PH), reduction of redox potential (EH), addition of preservatives (PRES), competitive flora and irradiation, and called these factors as the fence factor. Barrier technology and barrier factors have also been translated into barrier technology and barrier factors in China

Application of fence technology

for a long time, fence technology has been widely used in food processing and preservation. People just don't understand the problem from the concept of fence technology, but consciously or unconsciously integrate multiple fence factors into empirical food processing and preservation. Since the fence theory was put forward in the 1970s, many studies and practices have shown that the fence technology can be used not only for microbial control in food processing and preservation, but also for technological transformation and new product development in food processing and preservation. For example, to reduce energy consumption in the storage process of meat products, we can consider using factors with less energy consumption (such as aw and pH value) to replace factor T with high energy consumption, because the barrier factors that inhibit food microorganisms can be replaced with each other to a certain extent. For another example, in the processing of canned vegetables, the sterilization temperature (f) and sterilization time can be reduced by reducing the pH value. The reasonable combination of fence factors should not only inhibit microbial activities, but also improve the sensory quality, nutrition and economic benefits of products as much as possible

fence technology has been widely and successfully applied to meat processing at home and abroad, and there have been some research and practice in many areas such as fruit and vegetable processing, fruit and vegetable our machines, in fact, many experimental machines for testing storage and preservation, grain and its semi-finished products storage, food packaging and so on. It can be predicted that with the deepening of the research on fence theory and the successful application of fence technology in production, fence theory and technology will become an important guiding basis for food processing and preservation

4. Water activity

the microorganisms that affect the stability of food are mainly bacteria, yeast and mold. The growth and reproduction of these microorganisms require a minimum water activity. If the water activity of food is lower than this requirement, the growth and reproduction of microorganisms will be inhibited. When the water activity is below 0.60, most microorganisms cannot grow

when the water activity of food decreases to a value, it will inhibit the growth, reproduction or toxin production of microorganisms requiring water activity higher than this value, so that food processing can proceed smoothly. In the processing of fermented food, the water activity must be increased to above the water activity value required for the growth, reproduction and secretion of metabolites of beneficial microorganisms

chemical reactions and enzymatic reactions in food are one of the important reasons for the changes in food quality. Reducing the water activity of food can delay the progress of enzymatic browning and non enzymatic browning. Low water activity can inhibit the chemical changes of food and stabilize the quality of food

water activity not only affects chemical reaction and microbial growth, but also affects the texture of dry and semi dry food. For example, if you want to maintain the brittleness of biscuits, expanded corn and fried potatoes, prevent the caking of sugar, milk powder and instant coffee, as well as the bonding of hard candy and preserves, you should maintain an appropriate low water activity

to sum up, the water activity meter is mainly used in the following aspects: whether to dry the studio before low-temperature experiments:

1. Preservation and storage of all kinds of food, such as rice, noodles, beans, dehydrated vegetables, etc

2. Quality control in the production process, such as all kinds of meat products, fillings, fermentation, cans, etc

3. Ensure the brittleness of food and prevent caking and bonding, such as biscuits, milk powder, preserves, etc

4. predict the shelf life of various foods and add preservatives reasonably (about 0.85, which can be stored for a few days, about 0.72, which can be stored for 2-3 months, and less than 0.65, which can be stored for 1-3 years)

minimum water activity (AW value) necessary for the growth of some microorganisms

normal align=center> minimum aw value

normal align=center> bacteria

normal align=center> yeast

normal align=center> mold

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