selcuk j agr food sci Selcuk Journal of Agriculture and Food Sciences 2458-8377 2458-8377 Selçuk Üniversitesi Fermentation Technology Food Technology Fermantasyon Teknolojisi Gıda Teknolojileri Kefir Fermantasyonunun Yağsız Fındık Protein İzolatının Biyoaktif Bileşiklerinde ve Antioksidan Aktivitesinde Meydana Getirdiği Değişimler Kefir Fermentation-Induced Changes in Bioactive Compounds and Antioxidant Activity of Defatted Hazelnut Protein Isolate https://orcid.org/0000-0002-1461-7357 Ermiş Ertan İstanbul Sabahattin Zaim Üniversitesi https://orcid.org/0000-0000-0000-0000 İyibaş Senanur İSTANBUL SABAHATTİN ZAİM ÜNİVERSİTESİ https://orcid.org/0000-0000-0000-0001 Küçük İrem İSTANBUL SABAHATTİN ZAİM ÜNİVERSİTESİ https://orcid.org/0000-0000-0000-0002 Albayraktar Hilal İSTANBUL SABAHATTİN ZAİM ÜNİVERSİTESİ 04 28 2026 40 1 190 201 09 11 2025 03 23 2026 Copyright © 1991, Selcuk Journal of Agriculture and Food Sciences 1991 Selcuk Journal of Agriculture and Food Sciences

Bu çalışma, yağsızlaştırılmış fındık posasından elde edilen proteinlerin fonksiyonel özelliklerinin kefir fermantasyonu yoluyla iyileştirilmesini araştırmıştır. Analizler pH, titre edilebilir asitlik, protein içeriği, indirgeyici şekerler, fenolik ve flavonoid içerikleri, antioksidan aktivite ve antimikrobiyal etkileri içermiştir. Fermantasyon, fındık protein izolatlarının bileşimini ve işlevselliğini önemli ölçüde değiştirmiştir. Fermantasyon, sıvı fazda ölçülen suda çözünür protein içeriğinde %88'lik bir artışa neden olurken, titre edilebilir asitlik dört kattan fazla artmış ve pH'da düşüş gözlenmiştir. Toplam fenolik ve flavonoid içerikleri sırasıyla %53 ve %32 artarak antioksidan aktiviteyi artırmış ve üçüncü günde neredeyse iki katına çıkmıştır. İndirgeyici şeker içeriği de artmış ve ikinci günde zirveye ulaşmıştır. Bu iyileşmelere rağmen, fermente edilmiş örnekler E. coli ve S. aureus'a karşı belirgin bir antimikrobiyal etki göstermemiştir. Genel olarak, fındık protein izolatlarının kefir fermantasyonu, antioksidan ve fonksiyonel özellikleri iyileştirerek fonksiyonel gıdalarda potansiyel uygulamalarını vurgulamıştır. Biyoaktif bileşik üretimini optimize etmek için tanımlanmış mikrobiyal suşlarla ve daha uzun fermantasyon süreleriyle yapılacak ileri çalışmalar önerilmektedir.

This study investigated the enhancement of functional properties of proteins extracted from defatted hazelnut pulp through kefir fermentation. Analyses included pH, titratable acidity, protein content, reducing sugars, phenolic and flavonoid contents, antioxidant activity, and antimicrobial effects. Fermentation significantly altered the composition and functionality of hazelnut protein isolates. Fermentation caused an apparent 88% increase in measured water-soluble protein content in the liquid phase, while titratable acidity rose more than fourfold, accompanied by a pH decline. Total phenolic and flavonoid contents increased by 53% and 32%, respectively, enhancing antioxidant activity, which nearly doubled by the third day. The reducing sugar content also increased, reaching a peak on the second day. Despite these improvements, fermented samples showed no marked antimicrobial effects against E. coli and S. aureus. Overall, kefir fermentation of hazelnut protein isolates improved antioxidant and functional properties, highlighting their potential application in functional foods. Further studies with defined microbial strains and extended fermentation times are recommended to optimize bioactive compound production.

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