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

Abstract

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).