Comparison of vegan kefirs enriched with date seed powder with kefirs produced from cow milk in terms of physicochemical properties, free amino acid profile, organic acid profile and phenolic compound profile

In the current study, almond milk kefirs enriched with date seed powder were produced with the aim of incorporating kefir into the daily diet of individuals who cannot consume cow milk and who are vegan. This was done not only to address the nutritional deficiencies of plant-based milks but also to contribute to the recycling of date seeds, which are considered waste due to their unique composition. Very significant differences (P < 0.01) were detected in angiotensin converting enzyme (ACE) inhibitory activity, total nitrogen (TN), nitrogen soluble in 12 % trichloroacetic acid (TCAN), organic acids excluding acetic acid and all amino acids excluding glycine between the control groups and vegan kefirs with date seed powder. The addition of date seed powder to vegan kefir made a positive contribution to the physicochemical and microbiological properties, ACE inhibitory activity, proteolysis, free amino acid profile. Addition of date seed powder to vegan kefirs increased total solids (7.43–8.88 %), fat (3.05–3.68 %), protein (1.84–2.57 %) and ash (0.72–0.78 %) contents and Lactococci spp. (8.24–8.56 log cfu/g), Leuconostoc mesenteroides (6.35–6.86) and yeast (4.06–4.26) counts. The ACE inhibitor activity of kefir samples ranged from 21.86 to 37.04 %, TN values from 0.29 to 0.62, and TCAN values from 0.01 to 0.06. Additionally, the essential amino acid contents of kefir samples ranged from 300.12 to 2478.93 nmol/mL, and the non-essential amino acid contents ranged from 1019.01 to 4475.30 nmol/mL. In terms of phenolic compounds, it was observed that benzoic acid (149954.00 ng/mL) was dominant in kefirs produced from cow milk, and chlorogenic acid (5960.30–7064.49 ng/mL) was dominant in vegan kefirs with date seed powder, however, the addition of date seed powder to vegan kefirs generally increased the concentration of phenolic compounds.