Kefir production and optimization from apricot kernel milk

The aim of this study is to produce kefir from apricot kernel milk as an alternative functional product for vegan individuals, lactose intolerant, cardiovascular disease and diabetes patients, to be able to use apricot kernel milk as a functional raw material by substituting it with other vegetable milks and to be a preliminary study for future studies. Within the scope of the study, kefir samples formulated with different proportions of apricot kernel milk were produced and the microbial, chemical, sensory, physicochemical, textural, aroma and bioactive properties of these kefir samples were investigated. In this context, kefir was produced by using pure cow's milk and apricot kernel milk and the mixture of these two milk at different rates (25%, 50% and 75%) and stored at 4 °C for 21 days. As a result of these analyzes; as the ratio of apricot kernel milk increased in kefir samples, lower viscosity, consistency, firmness and other textural values were observed. It was determined that the numbers of lactobacilli, lactococci and yeasts in the samples with the addition of apricot kernel milk were at the desired level for probiotic products. It was determined that there were qualitative and quantitative differences in the volatile composition of the samples with the addition of apricot kernel milk, and an acceptable sensory result was obtained for all samples. As a result of antioxidant (by ABTS and DPPH methods) and ACE-inhibition activities performed on kefir samples, antioxidant and ACE inhibition activities increased as the ratio of apricot kernel milk increased. The levels of free amino acids and gamma-amino butyric acid (GABA) in kefir samples changed with the addition of apricot kernel milk. As the ratio of apricot kernel milk increased, the amount of many amino acids decreased, while the amount of Gln, Gly and Arg increased dramatically. As the ratio of apricot kernel milk increased, the amount of GABA decreased. It was determined that there was an increase in the amount of GABA in all samples with the increase levels of cow's milk and of storage time. Larger pores were observed in the microstructure (SEM) of the samples as the ratio of apricot kernel milk increased. For the color analysis; lightness (L*), redness (a*), whiteness index (WI) values were found to be lower in samples with a higher level of apricot kernel milk ratio, while yellowness (b*), color intensity (C), and hue (hue) values were found to be lower values were found to be higher in samples with high apricot kernel milk concentration. As a result of the studies, it has been concluded that apricot kernel milk can be used successfully in the production of plant-based fermented kefir, and it can be a good alternative and functional fermented product for individuals on a vegan diet or with lactose intolerance people.