EFFECT OF AGGLOMERATION PROCESS ON THE MOISTURE SORPTION ISOTHERMS AND THERMODYNAMICS PROPERTIES OF YOGHURT POWDER

Öz

In this study, the effect of different binders on the sorption behavior of agglomerated yoghurt powders was presented. Moisture sorption isotherms of non-agglomerated yoghurt powder and agglomerated yoghurt powders with lactose and distilled water were determined at 4, 20 and 40 °C temperature levels. Equilibrium moisture contents of powders were fitted to mathematical models such as Oswin, BET and GAB equations. Moisture sorption properties of agglomerated powders were found as different from control yoghurt powder. It was determined that powders are less hygroscopic at higher temperatures. Using lactose binders caused to increase in water sorption values of powders at higher water activity values. Thermodynamic properties such as isosteric heat of sorption, differential entropy, and enthalpy values were assessed to provide knowledge about the properties of water and energy requirement associated with sorption behavior. Isosteric heat values decreased with increasing of moisture content of yoghurt powders.

Anahtar Kelimeler

• Fluid bed agglomeration,yoghurt powder,binder effect,moisture sorption isotherm

AGLOMERASYON İŞLEMİNİN YOĞURT TOZUNUN NEM SORPSİYON İZOTERMİ VE TERMODİNAMİK ÖZELLİKLERİ ÜZERİNE ETKİSİ

Öz

Bu çalışmada farklı bağlayıcılar kullanarak aglomere edilen yoğurt tozların nem sorpsiyon özellikleri araştırılmıştır. Bu amaçla aglomere olmamış yoğurt tozu ile laktoz ve distile su bağlayıcıları kullanılarak aglomere edilmiş yoğurt tozlarının 4, 20 ve 40 °C sıcaklıklarda nem sorpsiyon izotermleri tespit edilmiştir. Denge bağıl nem değerleri Oswin, BET ve GAB modellerine uyarlanmıştır. Aglomere tozların nem çekme özellikleri aglomere olmamış (kontrol) yoğurt tozuna göre farklılıklar göstermiştir. Yoğurt tozlarının yüksek sıcaklıklarda daha az higroskopik olduğu belirlenmiştir. Bağlayıcı olarak higroskopik karakterdeki laktozun kullanılması saf suya kıyasla yüksek su aktivite değerlerinde nem sorpsiyon oranını arttırmıştır. İzosterik ısı, diferansiyel entalpi ve entropi değerleri gibi termodinamik kavramlar kullanılarak sorpsiyon davranışı, nem ve enerji gereksinimleri tespit edilmiştir. Yoğurt tozlarının nem içeriği arttıkça tüm tozlarda izosterik ısı sorpsiyonu değerlerinde azalma gözlemlenmiştir.

Anahtar Kelimeler

• Akışkan yatak aglomerasyon,yoğurt tozu,bağlayıcı etkisi,nem sorbsiyon izotermi

Kaynakça

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