Natural Lactic Acid Bacteria Research Articles

Indigenous Dadih Lactic Acid Bacteria: Cell‐Surface Properties and Interactions with Pathogens

Cell surface properties of dadih lactic acid bacteria strains were studied for adhesion to hydrocarbons (BATH) and aggregation abilities. Autoaggregation correlates with adhesion, which is a prerequisite for colonization and infection of the gastrointestinal tract by many pathogens, whereas coaggregation has been related to the ability to interact closely with pathogens. The results demonstrated significant differences in cell surface properties among the tested natural lactic acid bacteria food strains. Hydrophobicity increased when the cells were heat inactivated. All strains showed aggregation abilities with the pathogen strains tested, but the coaggregation properties were strain-specific. Our results indicate that the ability to autoaggregate, together with cell surface hydrophobicity and coaggregation abilities with pathogen strains, can be used for preliminary screening in order to identify potentially probiotic bacteria suitable for human or animal use. This study suggest the importance to identify and characterize bacterial cell-wall properties to understand their role in adhesion to hydrocarbons, autoaggregation and relation to coaggregation mechanisms, and also the relevance to future probiotic food development from natural strains.

Selection of starters for a traditional Turkish yayik butter made from yoghurt

Butter is produced from two different materials in Turkey, cream and yoghurt. The butter produced from fresh yoghurt or ‘tulum yoghurt’ (a strained yoghurt produced from cow, goat or sheep milk) is called ‘yayik butter’ and has been traditionally produced in Turkey for centuries. In this research, we attempted to isolate and identify the natural lactic acid bacteria (LAB) of yayik butter and to select the best LAB combination for butter production. Twenty samples of yayik butter were collected from Afyon, Antalya, Isparta and Konya regions in Turkey and determined to have a mean pH of 4·78±0·33, a mean titratable acidity (lactic acid) of 0·23±0·07% and a mean NaCl of 0·55±1·22%. The mean counts of LAB (log 10 cfu g −1) were 2·66±0·84 and 1·72±0·82 on MRS agar at 30 and 42°C, 2·44±0·93 and 1·78±0·24 on M17 agar at 30 and 42°C, and 1·64±1·196 on Sodium Azide Leuconostoc agar at 21°C, respectively. Eighty-five different LAB isolates were obtained from 20 yayik butters and identified as Streptococcus salivarius ssp. thermophilus (21·2%), Streptococcus sp. (4·7%), Lactobacillus delbrueckii ssp. bulgaricus (20%), Lactobacillus casei ssp. casei (15·3%), Lactobacillus paracasei ssp. paracasei (2·3%), Enterococcus faecium (18·8%). Leuconostoc pseudomesenteroides ( Leucono-stoc mesenteroides ssp. dextranicum) (7·1%), Leuconostoc gelidum ( Leuconostoc mesenteroides ssp. mesenteroides ) (4·7%) and Weissella paramesenteroides ( Leuconostoc paramesenteroides) (5·9%). Combinations of S. salivarius ssp. thermophilus S51, Lb. delbrueckii ssp. bulgaricus A42, Lb. casei ssp. casei K64, Lb. paracasei ssp. paracasei A27, and Leu. pseudomesenteroides E83 were used as starter bacteria for experimental butter production from cream. Six different groups of butters were produced using different combinations of these bacteria (B, C, D and E samples), commercial culture (F sample), and without culture (A sample). Sensory evaluations showed that the experimentally produced butter sample of group B was more acceptable than the other butters. In addition, the buttermilk of sample B had lowest fact content. LAB counts of experimental butters produced with combined cultures and commercial culture were similar (6·66±1·87–6·83±0·040 and 6·81±0·13 log 10 cfu g −1 on MRS agar, respectively).

Producing specific milks for speciality cheeses.

Protected denomination of origin (PDO) cheeses have distinctive sensorial characteristics. They can be made only from raw milk possessing specific features, which is processed through the 'art' of the cheesemaker. In general, the distinctive sensorial traits of PDO cheese cannot be achieved under different environmental-production conditions for two main reasons: (1) some milk features are linked to specific animal production systems; (2) cheese ripening is affected by the interaction between milk (specific) and the traditional technology applied to the transformation process (non-specific). Also, the environment for a good ripening stage can be quite specific and not reproducible. With reference to milk, factors of typicality are species and/or breed, pedoclimatic conditions, animal management system and feeding. Other factors that influence cheese quality are milk treatments, milk processing and the ripening procedures. The technology applied to most cheeses currently known as PDO utilizes only raw milk, rennet and natural lactic acid bacteria, so that milk must be, at its origin, suitable for processing. The specific milk characteristics that ensure a high success rate for PDO cheeses are high protein content and good renneting properties, appropriate fat content with appropriate fatty acid composition and the presence of chemical flavours originating from local feeds. Moreover, an appropriate microflora is also of major importance. The factors that contribute to achieving milk suitable for transformation into PDO cheese are genetics, age, lactation stage, season and climate, general management and health conditions, milking and particularly feeding, which affect nutrient availability, endocrine response and health status, and also the presence of microbes and chemical substances which enrich or reduce the milk-cheese quality. Many of these factors are regulated by the Producer Associations. However, the secret of the success of PDO cheeses is the combination of modern technology and tradition, with the objective of adapting the product to market demand, without losing specificity, originality and authenticity.

Complete Heterolactic Acid Fermentation of Green Beans by Lactobacillus cellobiosis

ABSTRACTOnly Lactobacillus cellobiosus, among eight strains of heterofermentative lactic acid bacteria, removed all fermentable sugars from green beans. Proper blanching of the beans was required to prevent growth by natural lactic acid bacteria. An inoculum of 10 CFU/ml Lactobacillus plantarum and 106 CFU/ml L. cellobiosus resulted in the formation of twice as much lactic acid as inoculation with L. cellobiosus alone. A maximum of 3.74% sugar was metabolized by L. cellobiosus in bean juice containing 2.5% NaCI and 0.08% acetic acid. Fructose was nearly quantitatively reduced to mannitol with a concomitant accumulation of acetic acid. Ethanol was not observed until most of the fructose was metabolized. The L. cellobiosus‐fermented beans had a more mild acid flavor than beans fermented with L plantarum.