Pınar Balkır

Spray Drying of Yogurt: Optimization of Process Conditions for Improving Viability and Other Quality Attributes

Plain yogurt was subjected to spray drying to determine the optimum processing conditions that yield maximum survival ratio of lactic acid bacteria, maximum overall sensory attributes, minimum color change, and acceptable moisture content. The inlet (150–180°C) and outlet air temperatures (60–90°C) and the feed temperature (4–30°C) were the independent factors. A pilot-scale spray dryer was used to conduct a set of drying experiments where the process conditions were selected according to central composite rotatable design (CCRD). The resulting yogurt powder at each condition was also subjected to the measurement of some physical properties (water activity, titratable acidity [lactic acid, %] and pH) to determine the effects of spray-drying conditions. The morphological structure of the powder was inspected by scanning electron microscopy (SEM) analysis. Optimization by the application of the desirability function method resulted in air inlet temperature of 171°C, air outlet temperature of 60.5°C, and feed temperature of 15°C as the optimum processing condition. The mathematical optimum condition was experimentally verified.

STEVIA; FONKSİYONEL ÖZELLİKLERİ VE GIDALARDA KULLANIM OLANAKLARI

Ilk olarak Paraguay’da hasat edilen, Stevia rebaudiana Bertoni bitkisinin yapraklarindan elde edilensteviol glikozitler, sakkarozun yaklasik 300 kati kadar tatliliga sahiptir. Stevia bitkisi icerisinde, bitkiyapraginin kurumaddesinin yaklasik %30’a kadarlik kismini olusturan on bir temel glikozit bulunmaktadir.Bunun yani sira kalori icermemesi ve saglik uzerinde cesitli olumlu etkilere sahip olmasi nedeniyle sonyillarda dunyanin bircok yerinde dogal tatlandirici olarak kullanimi yayginlasmistir. Ustelik steviolglikozitler, gidalarin islenmesi ve depolanmasi sirasinda tatliligini koruma ve cok farkli islem kosullarindastabilitesini kaybetmeme gibi ozellikleri acisindan ureticilere avantaj saglamaktadir. Gunumuzdedunyanin bircok yerinde stevia cay, alkolsuz icecekler, meyve sulari, yogurt, soya sutu, firinlanmisurunler, tahil urunleri, salata soslari, sekerleme urunleri gibi bircok islenmis gida urunlerinde kullanimininyani sira, sofra sekeri olarak da karsimiza cikmaktadir. Stevianin botanik ozellikleri, saglik uzerindekietkileri, yapraklarindan tatlandirici ekstraksiyonu ve gidalarda seker yerine kullanim olanaklarinin elealindigi bu derlemenin, yakin gelecekte ulkemizde yapilacak arastirmalara isik tutacagi dusunulmustur