Potential Use of Lactic Acid Bacteria (LAB): Protective Cultures in Food Biopreservation
Lactic acid bacteria (LAB) as protective cultures (PC) have emerged as a promising alternative to chemical preservatives due to their natural and food- grade benefits. Application in food products demonstrated the potential to control pathogenic and spoilage microorganisms. There is significant scope in biopreservation of feimented and minimally processed food products. The careful selection of culture and further optimization in food products enables the protection of food from spoilage, when storage temperature-abuse takes place.
The risk of food safety and loss of quality due to post-processing contamination with pathogens and spoilage microorganisms has increased besides the emergence of new food-borne pathogens. The storage of foods at low temperatures has been followed to preserve the foods without spoilage. However, the psychographic bacteria including pathogenic (L. monocytogenes) and spoilage (Pseudomonas) continue to grow at these temperatures. These days, the world food market is driven by consumers, who desire foods that are more convenient to store, ready-to-consume, least processed, and natural like a wide variety, nutritionally sound, and health-promoting . Thus, the chemical preservatives or artificial antimicrobials are frowned on as it is not compatible with natural image, which poses challenges to food processors. Thus, the approach to meet these demands is to use alternatives to chemical preservatives. Bacteriocins in pure or semi-pure forms are incorporated into foods as a natural preservative .
The application of bacteriocins in foods has popularized due to specific antimicrobial activity against pathogens. These are active at a wide pH range, tolerate high temperature, and believed to be degraded by enzymes in the human gastrointestinal tract (GIT). In some cases, incorporation of bacteriocins or other antimicrobial metabolites into foods adsorbs to the food constituents leading to loss of antimicrobial activity. Therefore, an alternative approach is the inoculation of food with food-grade bacteria capable to produce bacteriocins or other antimicrobial metabolites .
The importance and applications of lactic acid bacteria (LAB) in biopreservation of food through in situ production of antimicrobials are described in this chapter.
PROTECTIVE CULTURES (PC)
The benefit of using protective cultures (PC) as additives is chemical-free preservation, whenever the abuse of storage temperature takes place through the production of antimicrobial compounds within the food thus protect from microbial spoilages. The in-situ production of bacteriocins by viable bacteria enables to maintain desired concentration of bacteriocins with foods. It can overcome the problem of degradation of bacteriocins and unavailability due to binding to food constituents, when purified form is used as an additive [9, 28, 47]. Besides PC, being natural can tackle the emerging problem of antibiotic and preservative resistance in food chain. Moreover, the utilization of whole live PC could replace purified form of bacteriocin as the high expenses for isolation and purification restrict the wider use of novel bacteriocins on commercial scale and no specialized equipment are required . Incorporation of PC in minimally processed foods helps to ensure food safety and preserve the nutritional quality.
The PC are “live microorganisms that are deliberately inoculated into a product to control the microbiological status without significantly altering the technological and sensoiy quality.” PC may differ from starters by their lack of, or limited ability to transform the product. They produce antagonistic in situ that increases the competitiveness of producer, thereby contributes to control pathogen and food spoilage microorganisms. The principles for PC application in food products are :
- • Competitive Exclusion: This competes with indigenous microflora for readily fermentable nutrients and or binding sites on substrates, better adaptability to oxygen levels.
- • Production of Antimicrobial Substances: Bacteriocins (bacterioci- nogenic strains) and other fermentation products (organic acids, low molecular weight (MW) bioactive compounds, etc.).
- • Combination of Above Principles: Such bacteria are considered important to provide protection to food from spoilages by microorganisms and control pathogen.
To distinguish between bacterial cultures for usage as PC, the desirable properties are:
- • Cost factors;
- • Predictable metabolic activity under the given conditions;
- • Reliable production of antagonistics with broad spectrum of antimicrobial activity;
- • Serve as indicator for abused situation;
- • Should be able to grow at high levels by withstanding the intrinsic factors of food;
- • Should not affect product sensory;
- • Should not be harmful to humans: Non-pathogenic; Should not produce toxins, biogenic amines or any other metabolites;
- • Should show good growth at varying temperatures;
- • Should tolerate adverse conditions of processing and storage.