No abstract

Stirred-type fruit-flavored yogurt was made by adding cornelian cherry paste and sugar at different ratios. The effects of the paste and sugar addition on the physicochemical and organoleptic properties of yogurt were examined. The titratable acidity, pH, viscosity, whey separation, and organoleptic properties of experimental yogurts were determined at weekly intervals for 21 days. Statistically significant differences were found between the control and fruit-flavored yogurts in terms of viscosity and whey separation. The addition of the fruit paste and sugar to yogurt resulted in an increase in the whey separation, and a decrease in the viscosity. During the storage, the values of the titratable acidity, viscosity and whey separations of experimental yogurts increased, while pH of the yogurts decreased significantly (P < 0.01). Yogurt with 10 kg/100 kg fruit paste and 10 kg/100 kg sugar was more acceptable and high scored with respect to overall acceptability value by panelists; however the result was not significant statistically.

Fruit‐flavoured yoghurt was made by adding 2.5, 5.0, 7.5 and 10.0% mulberry pekmez (MP) into milk. The effects of the MP on the quality and fermentation process of the yoghurt were determined. The titratable acidity, pH, viscosity, whey separation and lactic acid bacteria (LAB) counts were determined at weekly intervals for 28 days. The pH range of the MP yoghurts was 4.65–5.57 and the pH of the plain yoghurt was 4.47 (P < 0.05). The addition of MP led to an increase in the fermentation time and a decrease in the viscosity of the yoghurts. Statistically significant differences were found between the plain and MP yoghurts in terms of pH (4.01 and 4.35), viscosity (5429 and 3175 cP) and number of LAB (7.07 and 6.48 log cfu). During storage, the titratable acidity, viscosity and LAB counts of MP yoghurts were lower and the whey separations higher than those of controls.

Five yogurt batches were prepared with banana puree and sugar combinations and ABT-2 (Streptococcus salivarius ssp. thermophilus, Lactobaccilus acidophilus and Bifidobacterium spp.) as starter culture. The addition of fruit influenced (P < 0.05) the syneresis, titratable acidity and pH, whereas the viscosity value, and S. salivarius ssp. thermophilus, L. acidophilus and Bifidobacterium spp. counts were found to be insignificant. Storage time significantly (P < 0.05) affected the syneresis, titratable acidity, pH value, and S. salivarius ssp. thermophilus counts, while the viscosity value and L. acidophilus and Bifidobacterium spp. counts were not affected. The sensory evaluations showed that the sample B was most preferred by panellists.

Volatile compound profiles of probiotic yogurt samples prepared using 8 different prebiotic combinations were analyzed using gas chromatography/mass spectrometry (GC-MS) with solid phase micro extraction during 28 days of storage. A total of 40 volatile compounds were identified in yogurt samples during storage consisting of 2 aldehydes, 6 ketones, 4 alcohols, 6 acids, 5 esters, 3 terpenes, 3 aromatic hydrocarbons, and 12 aliphatic hydro-carbons. Acetaldehyde, diacetyl, acetoin, 2-heptanone, ethanol, isoamyl alcohol, acetic acid, caproic acid, caprilic acid, and capric acid were the major volatile compounds in all probiotic yogurt samples.