REPLACEMENT OF NITRITES IN VACCUM-PACKED PASTEURIZED SAUSAGES WITH PROTECTIVE MICROBIAL CULTURES OF LACTOBACILLUS CURVATUS, LACTOCOCCUS LACTIS, BACTERIOSINS AND NATURAL COLOURANTS

摘要

The production of pasteurized sausages without use of nitrites, by adding bacteriocins or bacteriocin-producing cultures and natural colourants in order to achieve the desirable shelf-life, safety and curing colouring of sausages in the absence of nitrites. Pork sausages(PS) of lOOg were prepared as follows: PS-O: only with spices, without nitrites (blank) PS-1: without nitrites, with added ascorbate (0,1%), sodium lactate (1%) PS-2: with nitrites (0,5% curing salts) PS-3: without nitrites, with added nisin (0,1%) PS-4: without nitrites, with added 1% dispersion of nisin-producing Lactococcus lactis (106 cfu/gr) PS-5: without nitrites, with added 1% dispersion of curvacin-producing Lactobacillus curvatus(106 cfu/gr) PS-6:same as blank,but with added natural colourant "Natural RedE)"(blood protein powder 1%) Blank(PS-O) did not contain any colourant. Samples 1, 3, 4, 5 contained natural colourant "NATUREX VegStable~?"(vegetable extract). The samples were vaccum-packed, pasteurized at 72°C×11'(core temperature 72°C×3'), and preserved at 4°C×118 days (118d). Prior to pasteurization sausages had undergone a short maturation at 16°C×2d (for developing the protective culture).AIso,a temperature abuse scenario was implemented (preservation at 4°C×17d,10°C×4d,and 25°C×3h). Indicator-microorganisms were enumerated during preservation period (Psychrotrophs, Yeasts, Enterococci, Staphylococci-Micrococci, Enterobacteriacae, Pseudomonas, Sulphite-reducing Clostridia, Lactic acid bacteria, Brochothrix thermosphacta), as well as pathogens (S. aureus, C. perfringens, L. monocytogenes, S. typhimurium). Also, the pH and colour (L, a, b values) were measured. Samples were satisfactorily preserved up to ~68d. After 68d samples 1, 2 and 6, wich didn't contain nitrites or bacteriocins, developed spoilage (off-odour, yeasty or sour flavor). All were unacceptable (to varying degrees) by 118d. Adding L. curvotus dispersion was in most cases more effective than adding L. lactis, or pure nisin, indicating a broader antimicrobial activity by L curvatus. B. thermosphacta, as well as Enterococci, were good quality indicators after 68d(before that, their population was too low) and related, along with lactic acid bacteria, with the gradual decrease acidification of sausages. Conversely, Pseudomonads increased after significantly after 68d,increasing the pH, with simultaneous decline of lactic acid bacteria. Yeasts and psychrotrophs were good quality indicators throughout the storage period. Overall, similarly low numbers of the above indicators were observed in samples PS-2 (with nitrites) and PS-5 (with L. curvatus). Moreover, during temperature abuse, the populations of yeats, psychrotrophs, B. thermosphacta were significantly lower in PS-5 than PS-2. The pure solution of nisin (PS-3) or L. lactis dispersion (PS-4) were less effective. All samples were free of L. monocytogenes and Salmonella. However, samples 0,1, 6 contained 5. aureus above the allowed safety limits at 13d, and during temperature abuse, sample PS-0 contained C. perfringens above the allowed limits. As for the colour, a values (indicative of "redness") were similar (if not higher) in samples containing "NATUREX VegStable~?" compared with samples containing nitrites. The absence of colourants (blank) or addition of blood protein powder (PS-6) resulted in undesirable brown colour. Conclusively, the use of protective cultures of L curvatus (and to a lesser extend L lactis) led to satisfactory preservation of sausages until 68d, and in combination with colourant "NATUREX VegStable~?" could successfully replace nitrites in pasteurized sausages.