HIGH-TECH STARTER CULTURES IN MILK PROCESSING

L. DE VUYST^a)
a) Division of Industrial Microbiol., Ferment.Technol. and Downstream Processing, Department of Biotechnology, Faculty of Science, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium

Review paper
Language: English

ABSTRACT
Lactic acid bacteria are traditionally applied as starter cultures in industrial milk fermentation because of their favorable fermentation properties (lactose digestion, citrate utilization, proteolysis, bacteriophage resistance, slime production), their capacity to produce flavors (diacetyl, acetaldehyde), and their antimicrobial activity (organic acids, hydrogen peroxide, bacteriocins). Optimal physiological and process technological control of these metabolic traits allows the application of improved fermentation processes both in vitro and in situ. The use of molecular techniques and natural gene transfer methods has resulted in the selection and construction of lactic starter cultures with enhanced industrial properties. Moreover, novel lactic acid bacteria have been obtained by genetic, metabolic and protein engineering. This paper reviews the present state of the art and perspectives of engineering lactic acid bacteria for the improved production of milk products, flavors and additives.

BACTERIOCINS OF LACTIC ACID BACTERIA AS POTENTIAL BIOPRESERVATIVES

Bojana BOGOVIČ-MATIJAŠIĆ^a), Irena ROGELJ
^a) Univ. of Ljubljana, Biotechnical Fac., Zootechnical Dept., Groblje 3, SI-1230 Domžale, Slovenia

Review paper
Language: English

ABSTRACT
The production of antagonistic substances by lactic acid bacteria (LAB) is well known and LAB are widely used in food preserving. Among antagonistic substances bacteriocins are very interesting. The interest for use of bacteriocins of LAB as natural antimicrobial compounds has appeared mainly because some of them are able to inhibit certain Gram-positive spoilage bacteria and food borne pathogens like Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus and Clostridium butyricum. Bacteriocins of LAB could not fully substitute traditional preserving factors in food, but offer an additional hurdle. They can be introduced into foods as starter cultures, protective cultures or as additives in semi-purified, purified or pre-fermented form. Application of bacteriocins in foods is limited because of some characteristics: narrow activity spectrum, inactivation by proteolytic enzymes, binding to food components, too low "in situ" production, influence of intrinsic factors (pH, Aw), resistant strains. Some of those obstacles could be overcome by combining more bacteriocins or by genetically modifying bacteriocin producer. Until now only nisin and pediocins are industrially used, but many others are being tested on experimental level. Some promising examples of food preservation using bacteriocins or bacteriocins producing cultures are presented.

DETECTION OF ANTIBACTERIAL ACTIVITY OF COMMERCIAL LACTIC ACID STARTER CULTURES

Irena ROGELJ^a), Bojana BOGOVIČ-MATIJAŠIĆ, Andreja ČANŽEK
^a) Univ. of Ljubljana, Biotechnical Fac., Zootechnical Dept., Groblje 3, SI-1230 Domžale, Slovenia

Original scientific paper
Language: English

ABSTRACT
Twenty-one commercial starter cultures were tested for their antibacterial activity against 24 indicator bacteria. Specter of antimicrobial activity and probable presence of bacteriocin-like substances were detected with direct agar spot method. Thirteen of 21 tested commercial starter cultures have shown antibacterial activity against indicator bacteria, while the production of bacteriocin-like substance was found with starter cultures MSK B2, LA-CH-5, L. acid. 145 and MSK/V10. In cell-free supernatant no bacteriocin-like activity was detected. Strains of starter cultures BB 12, L. casei 01, LA-CH-5, L. casei R, MSK/V10 (L. acidophilus) were resistant at pH 2 - 5 and bile salts concentration 0,1% - 1,5%. The most promising as protective cultures or dietary adjuncts are among starter cultures tested L.casei 01, BB12, LA-CH-5, L.casei R, L.acid 145, MSK B2 and MSK/V10.

DECREASE OF CHOLESTEROL IN SOME CHEESE

I.F. VUJIČIĆ^a), Marija ŠKRINJAR, Mirjana VULIĆ, T. KÖNYVES, I. KURELJUŠIĆ, S. MIRECKI
^a) Poljoprivredni fak., Trg D. Obradovića 8, 21000 Novi Sad, Jugoslavija

Original scientific paper
Language: English

ABSTRACT
The occurrence of cholesterol decrease were examined during the ripening of cheese: Trappist, Kachkaval, goat’s Njeguški, and White. The amount of cholesterol during the ripening was gradually decreasing in all cheeses. The decrease in Trappist cheese after 14, 30 and 60 days was 35%, 40% and 45%, respectively; in Kachkaval cheese after 14 and 30 days was 17% and 27%, respectively; in Njeguški cheese after 14 and 45 days was 18 and 30%, respectively; in White cheese #1 after 7, 14 and 21 days was 25%, 28% and 32%, respectively; in White cheese #2 after 7, 14 and 21 days was 24%, 30% and 31%, respectively.

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