Author(s):
1. Milka Stijepić, JU Visoka medicinska škola Prijedor, Republic of Srpska, Bosnia and Herzegovina
2. Nikolina Malinović, JU Visoka medicinska škola Prijedor, Republic of Srpska, Bosnia and Herzegovina

Abstract:
Acidity is one of the most important characteristics of yoghurt quality and this parameter can have a very negative impact on the product quality. The purpose of the study was to examine the effect of the acacia honey addition in different concentrations (2%, 4% and 6%) in combination with 1% inulin and 1% whey protein concentrate and milk thermal treatment (85ºC/20min or 95ºC/10min) on the milk fermentation speed, inoculated with probiotic and yoghurt cultures in a concentration of 0.0025% w/w. Samples without supplements were also produced. Fermentation with mixed probiotic bacteria (Streptococcus thermophilus, Lactobacillus bulgaricus, Lactobacillus acidophilus and Bifidobacterium ssp.) was performed at 37ºC and with yoghurt cultures (Lactobacillus delbrueckii subsp. Bulgaricus and Streptococcus thermophilus) at 41ºC until pH 4.6 was reached. The samples were rapidly cooled to 20°C and placed in a refrigerator at 4°C±1. Measurements of the pH samples value (pH 510/mV Meter, Eutech Instruments Oakton, England) were performed on 1st ,7th, 14th, and 21st storage day. Differences in fermentation duration and speed were determined. The addition of inulin and whey protein concentrate, as well as their combinations with honey, significantly accelerated the fermentation process (p<0.05) compared to control samples, regardless of the applied milk thermal treatment. However, the different applied cultures did not affect the speed of milk fermentation. During storage in all probiotic samples and in traditional yoghurt (95ºC/10min), a significant difference in pH was observed (p <0.05) between samples on the 1st compared to 7th, 14th and 21st day. For traditional yoghurt samples whose milk was treated at 85ºC/20min there was no statistical difference with respect to the storage time. In general, the addition of honey, inulin and KPS significantly accelerated the fermentation speed, while in all samples during storage there was a stabilization of the change in pH value from the 7th storage day.

Key words:
yoghurt,probiotic,honey,inulin,KPS,pH

Thematic field:
Modern approach in sanitary engineering

Date of abstract submission:
04.03.2022.

Conference:
Međunarodna naučna konferencija - Znanjem do zdravlja SANUS 2022.