Is it better to have high or low levels of polyphenol oxidase PPO in fruits and vegetables?

In order to prevent the oxidation of fruits and vegetables and slow down the rate of oxidation, the lower the PPO content, the oxidation reaction.

The slower it progresses, the oxidase promotes the oxidation reaction.

Enzymatic browning is caused by the oxidation of orthophenol phenols to quinone under aerobic conditions due to the action of polyphenol oxidase (PPO), which quickly polymerizes to brown pigment and causes tissue browning. PPO is the main enzyme that causes enzymatic browning and is found in most fruits and vegetables. In most cases, due to the effect of PPO, it not only damages the perception of fruits and vegetables, affects the distribution of products, but also leads to a decrease in flavor and quality, especially in tropical fresh fruits, and direct economic losses caused by enzymatic browning.

up to 50%.

The amount of polyphenol oxidase (PPO) in fruits and vegetables should be neither too high nor too low, and should be determined on a case-by-case basis.

PPO is an enzyme that mainly promotes the oxidation of fruits and vegetables. In most cases, PPO can have a negative impact on the feel, flavour and quality of fruits and vegetables, especially in tropical fresh fruits, where enzymatic browning can cause direct economic losses of up to 50%. Therefore, in order to prevent the oxidation of fruits and vegetables and slow down the rate of oxidation, the lower the PPO content, the better.

However, in some cases, a high PPO content is advantageous. For example, in the production of black tea, it was found that PPO activity is strong and the polyphenol content is high, which is beneficial to the quality of black tea.

In summary, the content of PPO should be determined according to the specific application scenario.

Of course it's low, good, stupid one!

This question is very profound, I checked the information, please take a look: In plant tissues (such as apples, lychees, spinach, potatoes, beans, tea, mulberry leaves, tobacco, etc.), PPO is bound to the endocystic membrane, and is inactive in its natural state, but after homogenizing or injuring the tissue, PPO is activated, thus showing activity. In fruit and vegetable cell tissues, the location of PPO varies with the type, variety and maturity of raw materials, and most of the PPO activity in green leaves is present in chloroplasts [7]. Almost all of the subcellular fractions of potato tubers contain PPO, which is about the same as the protein fraction [8]; The former is mainly in the soluble PPO state in the cell fluid, while the latter is mainly in the chloroplast, mitochondria and other organelles, and is insoluble when combined with the membrane system or other specific parts of these organelles [9], and the effects of PPO activity and polyphenol content in tea shoots on the quality of black tea were studied, and it was found that the strong PPO activity and high polyphenol content were beneficial to the quality of black tea, and on the contrary, they were beneficial to the production of green tea [10]. In fresh apples, polyphenol oxidase is almost entirely present in chloroplasts and mitochondria.

PPOs prepared separately from these two fractions have slightly different substrate specificity [11]. Liu Qiangang believes that in addition to the presence of PPO in the cell on chloroplasts and mitochondria, there may also be PPO in the cell wall, and it has an impact on fermentation, and the cell has the effect of PPO as long as it is slightly damaged. Polyphenol oxidase is a plastid enzyme, and some researchers believe that polyphenol oxidase may be present only in plastids [12], and that polyphenol oxidase is absent in tissues lacking plastids, such as sieve tubes and sieve cells, but tissues with plastids may also not have polyphenol oxidase, such as C4 plant leaves.

Polyphenol oxidase is not necessarily present in plant tissues containing plastids, while polyphenol oxidase must be present in plant tissues containing plastids.

Polyphenol oxidase is a kind of redox enzyme widely distributed in nature, which is a class of copper-containing enzymes, which participates in the redox reaction at the end of respiration, and is closely related to the processing of agricultural and sideline products, the treatment of three wastes, and medicine and health. In 1990, Stephem Thanara studied the effects of PPO activity and polyphenol content in tea shoots on the quality of black tea, and found that strong PPO activity and high content of polyphenol oxidase were beneficial to the quality of black tea, so that the oxidation of polyphenol oxidase produced the unique color and aroma of black tea. In green tea, PPO activity is required to be lower to reduce the oxidation of polyphenols to keep the tea green and fresh. Therefore, people often need to study the content and characteristics of PPO in agricultural and sideline products in order to establish better processing technology.

Due to the high content of apple polyphenol oxidase, the tissue fluid is easily oxidized to brown, which masks the resulting color.

The tea has high polyphenol content and strong polyphenol oxidase activity.

The outer seed coat of Ginkgo biloba contains polyphenol oxidase.

Polyphenol oxidase is a proteosome that participates in a series of chemical changes caused by enzymatic activities in the life activities of tea plants and tea processing, so it is also known as a biocatalyst. The enzymes in tea are complex and have many types, including oxidoreductases, hydrolases, lyases, phosphorylases, transfer enzymes and isomerases. Enzyme proteins have the characteristics of general proteins, and are easily denatured and inactivated under high or low temperature conditions.

All kinds of enzymes have the optimal temperature range for their activity, and the enzyme activity is generally strongest in the range of 30C 50. If the enzyme is inactivated or denatured, it loses its catalytic ability. The catalytic effect of enzymes is specific, such as polyphenol oxidase, which can only oxidize tea polyphenols and polymerize into theaflavin, thearubigin and theabrownin, which are oxidation products of tea polyphenols; Proteases can only cause proteins to be broken down into amino acids.

Tea processing is to use the characteristics of enzymes to passivate or stimulate the activity of enzymes by technical means, so that they can undergo enzymatic reactions along the requirements of tea and obtain the unique color and flavor of various teas. For example, the greening in the process of green tea processing is to use the activity of high-temperature passivation enzyme to stop a series of chemical changes caused by enzymes in a short period of time, and form the quality characteristics of green leaf green soup. The fermentation in the processing process of black tea is the activity of the stimulating enzyme, which promotes the oxidative polymerization reaction of tea polyphenols under the catalysis of polyphenol oxidase to generate oxidation products such as theaflavins and thearubigins, and form the quality characteristics of black tea and red leaf red soup.

Yam is also rich in polyphenol oxidase.

At present, this technology has been successfully used to obtain potato strains without browning. In addition to the reports on apples, pears, tea, wheat and other crops, the research on polyphenol oxidase in other foods is also becoming more and more abundant, such as: tobacco, jujube fruit, bracken, eggplant, lotus root, banana, tomato.

Tea, apples, cassava, and lilies are also available.

Eating mangrass means eating grass from small animals.

The enzyme activity will not affect the final amount of the product under the premise that the reaction time is unlimited and the raw materials are limited, under the same reaction time and the same temperature conditions, the enzyme activity is low, and the yield is small.

The relationship between PPO and disease resistance has been extensively studied [32]. Resistance-related enzymes play an important role in the process of resisting the infection of pathogenic microorganisms, which mainly includes some enzymes in the phenolic metabolism system and pathogen-related protein family PPO through catalyzing the formation of lignin and quinone compounds, forming a protective shield to protect cells from pathogens, and can also directly exert anti-disease effects through the formation of quinones. So far, the more successful ones are:

Cucumber resistance to scab, apple's resistance to ring disease, banana's resistance to bunching disease, lemon's resistance to convective gum disease, sweet potato's resistance to vine cutting disease, rice's resistance to white leaf blight, and so on.

Among all the chemical components in tea, catechins and polyphenol oxidase are particularly important, except for green tea and yellow tea, the processing of all kinds of tea is based on the oxidation of catechins catalyzed by polyphenol oxidase, that is, the so-called "fermentation" process. Some scholars use young tea fruits as the carrier of exogenous PPO in the processing of black broken tea, and use a certain proportion in the processing process of black broken tea, and find that the TF content of the finished tea can be significantly increased and the TB content can be reduced. Some scholars have conducted research on endogenous enzyme fermentation, hoping to be applied in tea drinks to improve taste.

Polyphenol oxidase is the main enzyme that causes enzymatic browning of fruits and vegetables, and PPO catalyzes the oxidation of endogenous polyphenols in fruit and vegetable raw materials to produce melanin, which seriously affects the nutrition, flavor and appearance quality of products. These conditions are undesirable for both producers and consumers, and only in the production of a few food products are people use the role of PPO, such as polyphenol oxidase in tea, coffee, and black grapes. With the prominence of microbial fermentation, which has the characteristics of less investment, quick effect and easy control, the development of polyphenol oxidase in microorganisms has become a hot spot for researchers.

Laccase in microorganisms catalyzes the oxidation of various substrates such as phenols or aromatic amines, which makes them widely used in various fields such as the treatment of phenol-containing wastewater, the degradation of phenolic poisons in the environment, beverage processing, the production of edible and medicinal fungi, the feed industry, and medicine and health [33]. The use of microbial fermentation to synthesize tyrosinase has also become the direction of efforts to develop drugs for diseases such as white paralysis, Parkinson's disease and Alzheimer's disease.

Since there are a large number of polyphenols with different structures in nature, the polyphenol oxidase that catalyzes the oxidation of these phenolic substances is also different. It will be of far-reaching significance if effective enzyme sources are screened from microorganisms or effective microbial enzyme sources are created by enzyme modification, gene heterologous expression, and the construction of genetically engineered bacteria.