Ahmet Küçükçetin

Peptide profiling of bovine kefir reveals 236 unique peptides released from caseins during its production by starter culture or kefir grains

UNLABELLED Kefir has a long tradition in human nutrition due to its presupposed health promoting effects. To investigate the potential contribution of bioactive peptides to the physiological effects of kefir, comprehensive analysis of the peptide profile was performed by nano-ESI-LTQ-Orbitrap MS coupled to nano-ultrahigh-performance liquid chromatography. Thus, 257 peptides were identified, mainly released from β-casein, followed by αS1-, κ-, and αS2-casein. Most (236) peptides were uniquely detected in kefir, but not in raw milk indicating that the fermentation step does not only increase the proteolytic activity 1.7- to 2.4-fold compared to unfermented milk, but also alters the composition of the peptide fraction. The influence of the microflora was determined by analyzing kefir produced from traditional kefir grains or commercial starter culture. Kefir from starter culture featured 230 peptide sequences and showed a significantly, 1.4-fold higher proteolytic activity than kefir from kefir grains with 127 peptides. A match of 97 peptides in both varieties indicates the presence of a typical kefir peptide profile that is not influenced by the individual composition of the microflora. Sixteen of the newly identified peptides were previously described as bioactive, including angiotensin-converting enzyme (ACE)-inhibitory, antimicrobial, immunomodulating, opioid, mineral binding, antioxidant, and antithrombotic effects. BIOLOGICAL SIGNIFICANCE The present study describes a comprehensive peptide profile of kefir comprising 257 sequences. The peptide list was used to identify 16 bioactive peptides with ACE-inhibitory, antioxidant, antithrombotic, mineral binding, antimicrobial, immunomodulating and opioid activity in kefir. Furthermore, it was shown that a majority of the kefir peptides were not endogenously present in the raw material milk, but were released from milk caseins by proteases of the microbiota and are therefore specific for the product. Consequently, the proteolytic activity and the composition of the peptide profile can be controlled by the applied microflora (grains or starter culture). On the other hand, a considerable portion of the peptide profile was identified to be typical for kefir in general and independent from production parameters. In summary, the generated kefir peptide profile helped to reveal its origin and to identify bioactive peptides in kefir, which may advance the understanding of health benefits of this food product. The results further indicate that subsets of the kefir peptide list can be used as markers to control food authenticity, for example, to distinguish different types of kefir.

Oil production by Mortierella isabellina from whey treated with lactase

Whey, a by-product of cheese manufacturing is rich in nutrients such as lactose, proteins, and mineral salts. The fungus Mortierella isabellina was used for production of oil containing γ-linoleic acid (GLA) during fermentation on deproteinized whey permeate (DP-WP) with and without lactase addition. The maximum oil concentration was 3.65 g/L in DP-whey (16.0% lactose) without enzyme treatment. Treatment of DP-WP with lactase resulted in an increase in oil content to 17.13 g/L. Palmitic (22.50-25.80%) and oleic acids (37.60-48.56%) were the major fatty acids along with GLA (2.18-5.48%), linoleic (16.21-22.43%) and stearic acid (3.20-10.08%). This study suggests that whey can be utilized as a feedstock for production of microbial oil.

Physicochemistry, microbiology, fatty acids composition and volatile profile of traditional Söğle tulum (goat’s skin bag) cheese

Söğle cheese is a type of traditional tulum (goats skin bag) cheese produced from goats milk or a mixture of goats and sheeps milk in Küçük Söğle and Büyük Söğle villages, Antalya, Turkey. This is the first study that aimed to investigate the physicochemistry, microbiology, fatty acids composition and volatile profile of traditional Söğle cheeses ripened in goats skins for three months in wells. The pH and titratable acidity values, total solids, fat, protein and salt contents of the Söğle cheese samples ranged from 4.9 to 5.5, from 1.4 to 2.6%, from 46.5 to 55.0%, from 2.0 to 4.5%, from 34.9 and 42.2% and from 4.1 to 8.2%, respectively. The highest proportion of fatty acids in all cheese samples was palmitic acid (C16:0). The lactobacillus, lactococcus, total aerobic mesophilic bacteria and yeast and mold counts in the cheese samples were found to be between 7.1 and 8.5 log cfu/g, 7.8 and 8.7 log cfu/g, 7.6 and 8.5 log cfu/g and 1.0 and 4.8 log cfu/g, respectively. Fifty-three volatile components were identified in the cheese samples including 13 esters, 7 ketones, 5 acids, 2 aldehydes, 5 alcohols, 12 terpenes, and 9 miscellaneous compounds. Ketones and terpenes were the predominant volatile compounds.

Elektropüskürtme Yönteminin Probiyotik Mikroorganizmaların Mikrokapsülasyonunda Kullanımı

Probiyotik bir urunden beklenen faydalarin saglanabilmesi icin urunun raf omru sonuna kadar en az 10 8 -10 9 kob/g duzeyinde canli probiyotik mikroorganizma bulundurmasi gerekmektedir. Probiyotik mikroorganizmalari olumsuz kosullara karsi korumak amaciyla cok sayida yontem gelistirilmistir. Konu ile ilgili yapilan calismalar, probiyotik mikroorganizmalarin canliligini korumada en etkili yontemlerden birinin mikrokapsulasyon oldugunu gostermektedir. Bununla birlikte, mikrokapsulasyon islemi sirasinda probiyotik mikroorganizmalar yuksek sicaklik, dehidrasyon, yuksek osmolarite gibi olumsuz kosullara maruz kalabilmektedir. Elektrohidrodinamik atomizasyon yani elektroegirme ve elektropuskurtme yontemleri kullanilarak soz konusu olumsuz kosullarin ustesinden gelinebilmektedir. Son zamanlarda yapilan calismalarda; yuksek voltaj altinda kapsuller (elektropuskurtme) veya lifler (elektroegirme) uretilmesini saglayan elektrohidrodinamik atomizasyon tekniginin, probiyotik mikroorganizmalarin canliliklarinin korunmasi acisindan diger mikrokapsulasyon yontemlerine alternatif olabilecegi belirtilmistir. Bu derlemede, elektrohidrodinamik atomizasyon tekniginin temelleri ve elektropuskurtme yonteminin probiyotik mikroorganizmalarin mikrokapsulasyonunda kullanim olanaklari ile ilgili bilgi verilmesi amaclanmistir.

Bakteriyofajların Antibakteriyel Ajan Olarak Kullanımı

Dogada en fazla bulunan biyolojik topluluklardan birini temsil eden bakteriyofajlar, kendilerine ozgu hedef bakteriyi oldurebilen bakteri virusleri olarak tanimlanmaktadir. Bakteriyofajlar, 20. yuzyilin baslarinda bakteriyel enfeksiyonlarin tedavisinde kullanilmistir. Ancak, penisilinin kesfi ve antibiyotik endustrisinin gelismesi, bakteriyofajlarin antibakteriyel ajan olarak kullaniminin goz ardi edilmesine neden olmustur. Patojen bakterilerin antibiyotiklere karsi direnc kazanmasi, bakteriyofaj uygulamasini yeniden gundeme getirmistir. Son yillarda patojen bakterilere karsi bakteriyofajlarin kullanildigi ve “faj terapisi” olarak adlandirilan tedavi yonteminin gelistirilmesine yonelik calismalar hizla artmaktadir. Bakteriyofajlar, gidalarda patojen bakterilerin kontrolunde ve bazi ulkelerde hayvan ve insanlarda patojen bakteri enfeksiyonlari ile mucadelede antibakteriyel ajan olarak kullanilmaktadir. Bununla birlikte bakteriyofajlar, gidanin fizikokimyasal ozellikleri, koruyucu bilesenleri, depolama kosullari ve agiz yoluyla alinmalarindan sonra gastrointestinal sistemden gecisleri sirasinda yuksek asitlik, sindirim enzimleri ve safra gibi olumsuz etkilere maruz kalmalarindan dolayi aktivitelerini kaybetmektedir. Yapilan calismalar bakteriyofajlari, bilesenleri, fizikokimyasal ozellikleri ve depolama kosullari ile gidanin ve gastrointestinal sistemin olumsuz etkilerine karsi korumak icin mikrokapsulasyon yonteminin kullanilabilecegini ortaya koymustur. Bu derlemede, bakteriyofajlarin gidalarda antibakteriyel ajan olarak kullanimi ve mikrokapsule bakteriyofajlarin in vitro gastrointestinal sistem kosullarinda salinimlari ile ilgili bilgi verilmesi amaclanmaktadir.

Sütün Homojenizasyonunun Kefirin Fizikokimyasal ve Mikrobiyolojik Özellikleri Üzerine Etkisi

Bu calismada, tek veya cift kademeli dort farkli basincta (15, 15/5, 30 ve 30/5 MPa) homojenize edilen sutlerden uretilen kefirlerin fizikokimyasal ve mikrobiyolojik ozellikleri belirlenmistir. Kefir ornekleri 4°C’de 30 gun sureyle depolanmistir. Kefirlerin kurumadde, kul, yag ve protein icerikleri depolamanin 1. gununde; pH, titrasyon asitligi degerleri ile reolojik ve mikrobiyolojik ozellikleri ise depolamanin 1., 15. ve 30. gunlerinde belirlenmistir. Ayrica, farkli normlarda homojenize edilen sutlerde partikul boyutlari belirlenmistir. Homojenizasyon basinci ile kademe sayisi arttikca D[4,3] (µm) ve D[3,2] (µm) degerleri azalmis, spesifik yuzey alani degerleri ise artmistir. Kefir orneklerinde depolama suresi sonunda pH, viskozite, tiksotropi, kivam katsayisi degerleri ile laktobasil, laktokok, toplam mezofilik aerob bakteri ve maya sayilari azalmistir. Orneklerdeki en yuksek viskozite, tiksotropi, kivam katsayisi degerleri, tek kademede 15 MPa basincta homojenize edilen sutten uretilen kefir orneginde , en yuksek laktobasil, laktokok ve maya sayilari homojenizasyon islemi uygulanmayan sutten uretilen kefir orneklerinde saptanmistir.