The Application of Nisin in Plant Protein Products

Nisin, a natural antimicrobial peptide produced by Lactococcus lactis, is characterized by high efficiency, safety, and no residue, and is widely used in food preservation. In recent years, research on its application in plant protein products has gradually attracted attention, mainly reflected in the following aspects:

I. Inhibiting Microbial Contamination and Extending Shelf Life

Plant protein products (such as soybean protein products, pea protein products, and nut protein beverages) are rich in nutrients like proteins and carbohydrates, making them susceptible to contamination by microorganisms such as bacteria and molds, which leads to spoilage. Nisin has a strong inhibitory effect on Gram-positive bacteria (e.g., Listeria, Staphylococcus aureus, Bacillus), which are common spoilage or pathogenic bacteria in plant protein products.

For example, adding an appropriate amount of Nisin to meat substitute products made from isolated soybean protein can effectively inhibit the reproduction of spore-forming bacteria, delaying product rancidity and texture deterioration. In plant protein beverages (such as almond milk and walnut milk), when used in synergy with other preservation methods (e.g., moderate heat treatment, pH adjustment), it can reduce the survival of heat-resistant Gram-positive bacteria, significantly extending the product's shelf life.

II. Reducing Heat Treatment Intensity and Retaining Nutrition and Flavor

In traditional processing of plant protein products, high-temperature heat treatment is often used to achieve sterilization, but this can cause protein denaturation, amino acid destruction, as well as deterioration of product flavor (e.g., intensified beany flavor) and texture. The antimicrobial properties of nisin can reduce reliance on high-temperature treatment. Through the combined process of "low temperature + Nisin", it ensures sterilization effect while reducing the loss of nutrients and retaining the natural flavor and functional characteristics of plant proteins.

For example, in the production of pea protein yogurt, adding nisin can lower the post-fermentation sterilization temperature, avoiding the inactivation of probiotics and excessive protein coagulation, resulting in a more delicate texture and richer nutrition of the product.

III. Synergizing with Other Preservatives to Expand Antimicrobial Spectrum

Nisin has a weak inhibitory effect on Gram-negative bacteria, while plant protein products may be contaminated by Gram-negative bacteria such as Escherichia coli. In practical applications, it is often combined with other natural preservatives (e.g., lysozyme, plant polyphenols) or physical methods (e.g., high-pressure treatment) to expand the antimicrobial spectrum and enhance preservation effect.

For example, in soybean protein ice cream, the synergistic use of nisin and rosemary extract can not only inhibit Gram-positive bacteria but also exert inhibitory effects on some Gram-negative bacteria and molds, significantly improving the microbial stability of the product.

IV. Potential Function-Enhancing Effects

In addition to preservation, nisin may also play a role indirectly by regulating the processing properties of plant protein products. Studies have found that its addition can improve the emulsifying property and water-holding capacity of plant proteins to a certain extent, which may be related to the interaction between polar groups in its molecular structure and proteins. For example, in plant protein sausage products, the addition of nisin not only provides preservation but also helps maintain the elasticity and juiciness of the products.

V. Challenges and Optimization in Application

At present, the application of Nisin in plant protein products still has some limitations: first, its antimicrobial activity is easily affected by pH, temperature, and food components (e.g., fat, calcium ions), and its effect may decrease in alkaline or high-salt plant protein products; second, the addition amount needs to be strictly controlled, as excessive addition may cause a slight bitter taste or off-flavor. Therefore, in practical applications, it is necessary to optimize the addition amount of nisin according to the characteristics of different plant proteins (e.g., pH value, composition), and combine with process adjustments (e.g., microencapsulation technology) to improve its stability and effectiveness.

As a natural antimicrobial agent, nisin shows good application potential in the preservation, freshness-keeping, and quality maintenance of plant protein products. With in-depth research and technical optimization, its application in the field of plant protein processing will become more extensive.