1. The most important environmental factors

2. Rising temperature can accelerate food spoilage (chemical reactions and microbial growth and development speed are accelerated)

3. The impact on enzymatic reactions is complex

4. Prevent the aging of high-starch foods (the aging rate is fastest at 2~5℃)

5. Affect taste (softening)

1. High water activity affects the storage period and microorganisms are easy to reproduce.

2. Affect nutrients and flavor substances: High water activity is prone to enzymatic reactions, non-enzymatic browning, and oxidation reactions.

3. Affect appearance: water evaporation and dry consumption, leading to shrinkage and weight loss

4. Affects taste (moisture transfer)

1. Accelerate deterioration: accelerated fat oxidation

2. Reduced quality: fading, protein coagulation, vitamin changes, etc.

1. Microorganisms multiply easily and food spoilage speeds up.

2. Oxidation reaction reduces nutritional value and destroys pigments and flavor substances.

Enzyme activity is affected by temperature, pH, and water activity.

Ⅰ Oxidase

Ⅱ Lipase: Fat oxidizes and deteriorates, producing odor.

Ⅲ Pectinase: softens tissue and reduces quality.

Often occurs due to heating and long-term storage Mainly include Maillard reaction, caramelization reaction and ascorbic acid oxidation

Ⅰ Maillard reaction (carbonyl ammonia reaction)

Ⅱ Caramelization reaction: caused by excessive temperature

Ⅲ Ascorbic acid oxidation

1. Causes oxidation of fats, vitamins and pigments

2. Produce peculiar smell, resulting in deterioration of color and flavor, and reduction of nutritional value.

3. Fat oxidation will also produce some harmful substances

4. Related to factors such as temperature, light, metal ions, oxygen, moisture, etc.

5. Adding antioxidants can prevent or reduce oxidation

Common microorganisms in food

microbial control

Increase losses, contaminate food, and spread diseases

Affect appearance; promote decay; accelerate browning

ripen

Food safety issues (environmental pollution, pesticide residues, misuse of additives and packaging materials, etc.)