调味品中常用防腐剂及其抗菌性能的比较。

The preservation mechanism of food preservativesmainly acts on specific structural components of microorganisms, typically the cell membrane, and has a destructive effect on it. This disrupts the normal growth and metabolism of microorganisms, inhibiting their development and reproduction, thereby extending the shelf life of products. However, preservatives can also cause varying degrees of damage to human cells, so their usage must be limited.

Seasonings contain rich nutritional components such as proteins, fats, and carbohydrates, making them susceptible to attacks by various microorganisms like bacteria, yeasts, and molds, which can lead to spoilage and degradation.

There are many types of preservatives, but with the increasing emphasis on the safety of preservatives by the government, the use of each preservative is strictly regulated in China, resulting in a limited variety applicable to the seasoning industry. According to the GB 2760-2014 food additive hygiene standards, the main preservatives that can be used in seasonings include the following:

Benzoic acid and sodium benzoate are currently the most widely used preservatives in the seasoning industry, due to their good antibacterial effects and low cost, although their safety has been questioned.

Sodium benzoate can be used in the seasoning industry for soy sauce, vinegar, pickled vegetables, condiments, and low-salt pickles. The GB 2760-2014 food additive hygiene standard specifies a maximum usage of 1.0 g/Kg in seasonings, with typical usage ranging from 0.3 to 0.5 g/Kg.

Sorbic acid, also known as sorbate, exhibits inhibitory effects on molds, yeasts, and aerobic bacteria under acidic conditions. Sorbic acid is an unsaturated fatty acid that can participate in normal metabolic processes in the body and is assimilated into carbon dioxide and water. It can be regarded as a food component with no adverse effects on food flavor. Its toxicity is only 1/4 that of benzoic acid, making it an internationally recognized excellent preservative. Due to its moderate price and good safety, it has become a mainstream preservative in developed countries like the U.S. and Europe.

In the seasoning industry, it can be used in soy sauce, vinegar, and low-salt pickles. The GB 2760-2014 standard specifies a maximum usage of 1.0 g/Kg in seasonings, with typical usage ranging from 0.3 to 0.5 g/Kg.

Calcium propionate is a food antifungal agent that is notably effective in inhibiting molds and is used in soy sauce and vinegar to prevent spoilage. The GB 2760-2014 standard specifies a maximum usage of 2.5 g/Kg in seasonings, with typical usage ranging from 0.1 to 0.3 g/Kg.

Sodium diacetate is a white crystalline powder that is almost odorless. It is stable to light and heat, and its antibacterial capacity varies with pH but is not significantly affected by other factors, acting on both spoilage bacteria and pathogens. It is especially effective against molds and yeasts.

In the seasoning industry, it is widely applied. The GB 2760-2014 standard specifies a maximum usage of 10.0 g/Kg (for compound seasonings), with typical usage ranging from 0.1 to 0.5 g/Kg.

Natamycin is an amphoteric substance with one acidic and one basic group in its molecular structure. It is almost insoluble in water and most organic solvents but can dissolve easily in dilute acid and base solutions. Due to its cyclic molecular structure, the stability of natamycin is influenced by light, temperature, heavy metals, and pH. It should be used within a pH range of 4 to 7, avoiding high temperatures and light.

Natamycin is a specific and highly effective antifungal agent, showing strong inhibitory effects against almost all yeasts and molds. Its mechanism involves binding to ergosterol in the cell membrane, forming a complex that alters membrane structure and permeability, causing leakage of intracellular electrolytes and amino acids, ultimately leading to cell death.

Lactocin is very stable under acidic conditions, especially at pH < 2.0, where it can withstand sterilization at 121°C without losing activity. However, at neutral and alkaline pH, its activity is mostly lost after sterilization. Its solubility is closely related to pH, increasing as pH decreases.

Lactocin shows excellent inhibitory effects against most Gram-positive bacteria, particularly against Staphylococcus aureus and Bacillus species. It can act on bacterial cell membranes to form pore structures, disrupting the balance between the inside and outside of the cell, leading to cell death. It can also inhibit the synthesis of peptidoglycan, hindering cell wall formation and thus inhibiting cell growth.

When selecting preservatives, in addition to considering safety and economic factors, their antimicrobial efficacy and range of activity are also important aspects to focus on. To compare the antimicrobial effects of commonly used preservatives in seasonings, we measured the minimum inhibitory concentrations (MIC) experimentally and compared the inhibitory effects of each preservative.

Under acidic conditions, sodium benzoate and potassium sorbate show ideal inhibitory effects against bacteria, yeasts, and molds, while calcium propionate exhibits general inhibition against bacteria and yeasts but is particularly effective against molds. Sodium diacetate shows less efficacy against bacteria, but its inhibitory effects on yeasts and molds are better than those of sodium benzoate and potassium sorbate. Furthermore, sodium benzoate and potassium sorbate show similar levels of inhibition against bacteria, yeasts, and molds.

Natamycin demonstrates strong inhibitory effects against nearly 500 types of molds, with the majority being inhibited at concentrations of 0.50 to 6.00 mg/kg. Only a few molds are inhibited at concentrations of 10.00 to 25.00 mg/kg, with the minimum inhibitory concentration against Aspergillus species at 0.63 mg/kg, against black Aspergillus at 1.80 mg/kg, and against Penicillium islandicum at 1.10 mg/kg. It exhibits significant inhibitory capacity against fungi, with a minimum inhibitory concentration of approximately 1 mg/L.

Salad dressing, being semi-solid and high in fat content, is prone to mold spoilage during the summer. Experiments have shown that adding 10 ppm (0.001%) of natamycin can effectively inhibit mold growth. Considering losses during production, a suggested addition rate is 0.002%.

Research indicates that when the pH is acidic, lactocin at concentrations above 10 μg/mL shows some inhibitory effects against Listeria monocytogenes.

Thus, it is evident that different preservatives have their own advantages in terms of antimicrobial capability. In practical applications, choices can be made based on production needs, taking into account safety and cost, and it may also be feasible to combine two or more preservatives within the limits set by national standards.