What is the fresh-keeping principle for edible fungi? This article will help you understand it clearly
Fresh-keeping for edible fungi (theprincipleoffresh-keepingforediblefungi): Mushroom bodies separated from the culture substrate still have vitality, and living organisms have resistance to adverse external environments and microbial infection. However, the stronger the life activity, the faster the rate of freshness decline. Therefore, without destroying the normal physiological functions of the organism, by controlling various factors that affect the physiological and biochemical changes of fresh mushroom products, the life activity of the mushroom body can be kept at its lower limit, thereby extending its shelf life. The physiological basis for the decline in freshness of edible fungi:
1. Growth and development: Normally growing young and tender mushroom bodies will continue to complete their development process whether harvested or not. For example, Agaricus bisporus can continue growing from the second developmental stage at harvest through to the third to seventh developmental stages, with button mushrooms becoming old, flattened mushrooms. The developmental pattern is determined by genetic genes, but the speed of the process is restricted by environmental conditions.
2. Respiration: The physiological and biochemical changes of fresh mushrooms after harvest are directly or indirectly related to respiration. Respiration is a chain of biological oxidation-reduction reactions in metabolism catalyzed by enzymes, including aerobic respiration and anaerobic respiration. Respiratory products include carbon dioxide, water, ethanol or formaldehyde, etc., and release respiratory heat. Respiratory substrates are carbohydrates, organic acids, fats, etc., among which mannitol is an important substrate for the respiratory reactions of edible fungi. Respiratory intensity is expressed as the amount of carbon dioxide released or oxygen absorbed per unit weight of product per unit time, generally 200-500 mg carbon dioxide/kg fresh mushrooms per hour at 20°C. In addition to environmental factors, respiratory intensity is related to variety and fruiting body maturity. The respiratory quotient (RQ) refers to the volume ratio of oxygen absorbed to carbon dioxide released, VCO2/VO2, from which the magnitude of the ratio can be used to estimate whether it is aerobic respiration or anaerobic respiration.
3. Browning: Enzymatic browning is the main type. The simultaneous presence and mutual contact of active phenol oxidase, free oxygen molecules, and substrates with hydroxyl groups (edible fungi have 15-16 kinds of phenolic substances) are necessary conditions for enzymatic browning. After harvest, colorless phenolic substances in the mushroom body are oxidized into reddish-brown quinones and water, and the quinones undergo further oxidation and polymerization to form dark brown substances. The non-enzymatic autoxidation Maillard reaction of carbohydrates and lipids also causes discoloration and produces off-flavors.
4. Microbial infection: Causes physiological diseases, deterioration, and spoilage of the mushroom body. The main factors affecting the physiological and biochemical changes after harvest include temperature, relative humidity, gaseous environment, and pH, etc. Various factors comprehensively affect the process of change, and appropriate control will help curb the deterioration process.