Physical and microbial factors affecting the stability of vegetable protein drinks

Vegetable protein drink is a complex protein colloid system, and also a thermodynamically unstable system. The system includes suspension formed by protein, emulsion formed by fat, and true solution formed by sugar, salt, etc.

Therefore, during the production and storage of vegetable protein drinks, protein denaturation, precipitation, fat floating and other phenomena are prone to occur, leading to stratification, flocculation and coalescence of the system, which will significantly reduce product quality. The stability of vegetable protein drink is affected by many factors, but in general, it mainly includes chemical, physical and microbial factors.

1.1 Temperature

Temperature is a common factor leading to protein denaturation, which affects the stability of vegetable protein drinks, and both low and high temperature can lead to protein denaturation. When raw materials are stored below 0℃, the denaturation of proteins occurs, which may be related to the hydrophobic interaction of proteins, leading to the dissociation and rearrangement of some functional groups.

At high temperature, there will be violent movement between molecules, and the bonds that stabilize the advanced structure of proteins (such as hydrophobic interaction and electrostatic interaction) are easy to be interrupted. The hydrophobic groups of proteins are exposed from the inside, and the interaction between proteins and water molecules is weakened, and the solubility of proteins decreases.

Therefore, in order to meet the production requirements, the production process should be as short as possible heating time, rapid cooling after sterilization, and improve the interaction between proteins and lipids, is conducive to reducing the degree of protein denaturation, in order to improve the stability of the product.

The stability of vegetable protein drink is closely related to the particle size of dispersed phase. Stokes' law shows that the velocity at which a particle settles or rises is proportional to the square of its radius.

The larger the particle size is, the easier it is to precipitate due to gravity. However, when the particle diameter is less than 0.2μm, Brownian motion is generated in solution, which is conducive to the stability of solution.

According to Stokes' law, for a particular vegetable protein drink, particle density is constant; Medium density and viscosity change little, can also be regarded as constants.

Therefore, the larger the particle size of vegetable protein drink, the greater its settling speed. The non-rancidity precipitation stratification in vegetable protein drinks is mostly caused by the large particle diameter, the accelerated sedimentation rate and the destruction of sedimentation balance.

02 Microbial factors

Microorganisms are usually one of the important factors affecting the stability of vegetable protein drinks. In non-fermented vegetable protein drinks, if there is no sterilization, microorganisms are easy to cause the spoilage of products. Common bacteria causing spoilage of vegetable protein drinks include Pseudomonas, Proteus, Clostridium, etc.

In order to avoid the damage caused by microorganisms, the measures to be taken are to strengthen the quality control and hygiene management in the production process of vegetable protein drinks and standardize the sterilization process.

In commercial production, if sterilization is not complete in the production of vegetable protein drinks, microorganisms will grow and multiply under appropriate temperature conditions, leading to product spoilage. If the sterilization temperature is too high or the sterilization time is too long, it may lead to protein denaturation, fat oxidation, resulting in product viscosity decline, stability deterioration, and color darkening.

In order to ensure the safety of the product, have to sacrifice its color and other sensory quality, at the same time, to ensure the stability of the product, usually need to add carboxymethyl cellulose sodium stabilizer.

At present, the common fermented vegetable protein drink is lactic acid bacteria fermentation products. Lactic acid bacteria mainly ferment carbohydrates to produce lactic acid.

Due to the presence of starch, insoluble carbohydrates will reduce the stability of the product, from this point of view, lactic acid bacteria fermentation is beneficial to the stability of vegetable protein drinks.

On the other hand, the production of lactic acid leads to a decrease in the pH of the product, which may lead to a change in the protein structure and precipitate.

Vegetable protein drinks are more and more popular among consumers because of their rich protein and amino acids, unsaturated fatty acids, no or less cholesterol, and comprehensive and reasonable nutrition.

In recent years, Chinese plant protein drink made great progress. However, in the whole beverage market, the share of vegetable protein drinks is still insufficient, and the overall market capacity is low, far behind fruit juice, tea, carbonated drinks; In addition, at present, the vegetable protein drink market is almost completely occupied by soy milk, walnut milk, apricot milk, coconut water, peanut milk and other 5 kinds of vegetable protein drink, vigorously develop other kinds of vegetable protein drink, such as corn protein drink, potato protein drink, etc., enrich the product types, and expand the scope of vegetable protein drink and expand the market capacity is imperative.

The development of various kinds of vegetable protein drinks is conducive to improving the processing level and added value of agricultural products, which can not only meet the needs of people with different tastes and preferences, but also have practical significance to improve farmers' income and solve the problems of agriculture, rural areas and rural areas.

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2023-2-2

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