Problems posed by essential food preservatives

Review : Bacteriocinogenic lactic acid bacteria associated with meat products / Revisión: Bacterias lácticas productoras de bacteriocinas asociadas a productos cárnicos

Meat consumption is of great economical importance. Several lactic acid bacteria associated with meat products are important natural bacteriocin producers. Bacteriocins are proteinaceous antag onistic substances considered to be important in the control of spoilage and pathogenic microor ganisms. This review aims to present the current state of the art in terms of bacteriocinogenic lactic acid bacteria associated with fresh and fermented meat products, describe the biochemical and genetic characteristics of their bacteriocins and the potential use of bacteriocins production of meat products.

Effect of microGARD on keeping quality of direct acidified Cottage cheese

Direct acidified Cottage cheese could be kept well for only 10 to 12 days under refrigeration on account of its high moisture (~74 %) content and relatively high pH (~5.0). The study was, therefore, undertaken to improve the keeping quality of direct acidified Cottage cheese using MicroGARD. The effects of three different levels of MicroGARD 400 viz. 0.20, 0.35 and 0.50 % on the physico-chemical, microbiological and organoleptic properties were studied at four-day interval during storage under refrigeration (4-5 °C). Promising results were found using 0.50 % MicroGARD 400 for inhibiting psychrotrophs, yeasts and molds as well as retard the acidity development and proteolysis in Cottage cheese, thus extending its keeping quality. It was observed that addition of MicroGARD 400 at the level of 0.50 % considerably improved the flavour as well as the aesthetic quality of the product during storage and extended the shelf life of Cottage cheese from 12 to 26 days.

Antimicrobial activity of lactic acid bacteria isolated from Tenerife cheese: initial characterization of plantaricin TF711, a bacteriocin-like substance produced byLactobacillus plantarumTF711

AIMS

The screening and initial characterization of bacteriocins produced by lactic acid bacteria (LAB) from raw Tenerife goats' cheese with possible application as biopreservatives or ripening accelerators for Tenerife cheese.

METHODS AND RESULTS

One hundred and eighty LAB of the genera Lactobacillus (95), Leuconostoc (64) and Lactococcus (21) isolated from raw Tenerife goats' cheese were screened for the production of antimicrobial substances. Lactobacillus plantarum TF711, which had the broadest spectrum of antimicrobial activity, was selected for further characterization. The antimicrobial compound was determined as a proteinaceous substance, as it was sensitive to proteases. The bacteriocin-like substance, which we called plantaricin TF711, was active against the Gram-positive bacteria Bacillus cereus, Clostridium sporogenes and Staphylococcus aureus; and against the Enterobacteriaceae Shigella sonnei and Klebsiella pneumoniae. It was stable to heat and to treatment with surfactants and organic solvents. Highest antimicrobial activity was found between pH 1 and 9. Plantaricin TF711 exhibited primary metabolite kinetics, a bacteriostatic mode of action and a molecular mass of c. 2.5 kDa as determined by tricine SDS-PAGE.

CONCLUSIONS

Lact. plantarum TF711 produces a low molecular mass bacteriocin-like compound with a wide spectrum of activity and interesting technological properties (thermostability, good pH stability and stability against surfactants and organic solvents).

SIGNIFICANCE AND IMPACT OF THE STUDY

Plantaricin TF711 was found to have potential for use as a biopreservative in the food industry.

Antimicrobial peptides of lactic acid bacteria: mode of action, genetics and biosynthesis

A survey is given of the main classes of bacteriocins, produced by lactic acid bacteria: I. lantibiotics II. small heat-stable non-lanthionine containing membrane-active peptides and III. large heat-labile proteins. First, their mode of action is detailed, with emphasis on pore formation in the cytoplasmatic membrane. Subsequently, the molecular genetics of several classes of bacteriocins are described in detail, with special attention to nisin as the most prominent example of the lantibiotic-class. Of the small non-lanthionine bacteriocin class, the Lactococcus lactococcins, and the Lactobacillus sakacin A and plantaricin A-bacteriocins are discussed. The principles and mechanisms of immunity and resistance towards bacteriocins are also briefly reported. The biosynthesis of bacteriocins is treated in depth with emphasis on response regulation, post-translational modification, secretion and proteolytic activation of bacteriocin precursors. To conclude, the role of the leader peptides is outlined and a conceptual model for bacteriocin maturation is proposed.

Effect of some syrup constituents on the solubility of sorbic acid

The effects of sucrose, glucose, sorbitol, and saccharin on the aqueous solubility of sorbic acid at 20 and 37 degrees C were determined. Sucrose, glucose, and sorbitol decreased the solubility of sorbic acid with increasing concentrations at both temperatures. Increasing the concentrations of these sweetening agents resulted in decreases in the dielectric constants. Calculation of the free energy and enthalpy changes indicated that the dissolution process for sorbic acid became progressively unfavorable with increasing sugar concentration.