Physicochemical and Rheological Properties of Commercial Kefir Drinks

Year 2020, Volume: 18 Issue: 4, 375 - 381, 31.12.2020

Oğuz Gürsoy , Kübra Kocatürk Hande Özge Güler Dal Hasne Nazlı Yakalı Yusuf Yılmaz

https://doi.org/10.24323/akademik-gida.850881

Cited By: 9

Abstract

Kefir is one of the most preferred fermented beverages, and its production constitutes a significant portion of the dairy industry. In this study, the physicochemical and rheological properties of commercial plain kefir drinks were compared. Kefir drinks of dominant brands in the Turkish kefir market (n=6) were obtained from national markets, and samples with different production dates for each brand were used as replications. The ranges for the dry matter, protein and fat contents (%) of kefir drinks were 9.49-11.97, 2.30-3.44 and 2.50-3.00%, respectively. Moreover, the pH values of samples were in a range between 3.86 and 4.06 while their total titratable acidity (%, lactic acid) values ranged from 0.71 to 0.93%. Significant differences were found among the physicochemical properties of commercial kefir drinks (p<0.05). Rheological analyses were conducted at three different temperatures (4.0, 10.0 and 25.0±0.3°C), and the power law model was used to interpret the rheological characteristics of kefir drinks, which resulted in high coefficient of determination (R2) values. Besides, the apparent viscosity values of samples (at a shear rate of 111.6 s-1) were inversely related to temperature and varied between 0.48 and 1.76 mPa.s (p<0.05). Activation energy values of samples were between 21.51 and 36.18 kJ/mol. Significant differences in physicochemical and rheological properties were found among the commercial kefir samples of different brands, indicating the compositional variations of raw materials and kefir cultures used in their production.

Keywords

Kefir, Fermented milk, Consistency, Rheological behavior, Viscosity

Thanks

The authors thank to Cahit Burak KÜCÜKİGCİ for his technical support on the total nitrogen analyses of the present study.

Ticari Kefirlerin Fizikokimyasal ve Reolojik Özellikleri

Abstract

Kefir, fermente içecekler içerisinde en çok tercih edilenlerden biri olup üretimi süt endüstrisinde önemli bir yer tutmaktadır. Bu çalışmada, ticari sade kefirlerin fizikokimyasal ve reolojik özellikleri karşılaştırılmıştır. Türkiye ticari kefir pazarında etkili olan markalara ait kefirler (n=6) Türkiye'deki ulusal marketlerden temin edilmiş ve her bir marka için farklı son kullanma tarihlerine sahip örnekler tekerrür olarak kullanılmıştır. Ticari kefir örneklerinin kuru madde, protein ve yağ içeriklerine ait aralıklar, sırasıyla %9.49-11.97, %2.30-3.44 ve %2.50-3.00 olarak bulunmuştur. Örneklerin pH değerleri 3.86-4.06 aralığında, toplam titre edilebilir asitlik (%, laktik asit) değerleri %0.71-0.93 arasında saptanmıştır. Farklı markalara ait ticari kefir örneklerinin fizikokimyasal özelliklerinde önemli değişiklikler saptanmıştır (p<0.05). Farklı sıcaklıklarda (4.0, 10.0 ve 25.0±0.3°C) yapılan reolojik analizlerde, kefir içeceklerinin reolojik özelliklerinin yorumlanmasında yüksek R2 değerlerinin elde edildiği Üssel Kural (Power Law) modeli kullanılmıştır. Örneklerin (111.6 s-1 kayma oranındaki) görünür viskozite değerlerinin sıcaklıkla ters orantılı olduğu ve 0.48 ile 1.76 mPa.s arasında değiştiği saptanmıştır (p<0.05). Örneklerin aktivasyon enerjisi değerleri 21.51 ve 36.18 kJ/mol arasında değişmiştir. Farklı markalara ait ticari kefir örneklerinin fizikokimyasal ve reolojik özellikleri arasında önemli farklılıklar belirlenmiş olup, bu farklılığın da üretimde kullanılan farklı hammadde ile kefir kültürlerinden kaynaklanabileceğini göstermiştir.

Keywords

Kefir, Fermente süt, Kıvam, Reolojik özellik, Viskozite

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