EFFECT OF TOTAL SOLIDS AND FAT CONTENTS ON TITRATABLE ACIDITY AND SENSORY PROPERTIES OF SET-TYPE YOGHURT
RYM SALAH *
Department of Biochemistry and Microbiology, Faculty of Biological and Agronomical Sciences, Mouloud Mammeri University of Tizi-Ouzou, P.O.Box 17, RP 15000 Hasnaoua, Tizi-Ouzou, Algeria.
RACHIDA MAHMOUDI
Department of Biochemistry and Microbiology, Faculty of Biological and Agronomical Sciences, Mouloud Mammeri University of Tizi-Ouzou, P.O.Box 17, RP 15000 Hasnaoua, Tizi-Ouzou, Algeria
WASSILA MANCER
Department of Biochemistry and Microbiology, Faculty of Biological and Agronomical Sciences, Mouloud Mammeri University of Tizi-Ouzou, P.O.Box 17, RP 15000 Hasnaoua, Tizi-Ouzou, Algeria.
DJABER TAZDAÏT
Department of Biochemistry and Microbiology, Faculty of Biological and Agronomical Sciences, Mouloud Mammeri University of Tizi-Ouzou, P.O.Box 17, RP 15000 Hasnaoua, Tizi-Ouzou, Algeria.
*Author to whom correspondence should be addressed.
Abstract
The aim of this paper was to assess the effects of various concentrations nonfat dried milk (NFDM) and fat content (FC) on titratable acidity and organoleptic and physical attributes (taste, texture, syneresis and smell) of set-type yoghurt. The effect of raw milk addition to reconstituted milk on the same organoleptic and physical attributes was also assessed. In this study, dried powdered milk (26% fat), fresh cow milk and freeze-dried mixed yoghurt culture (Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus) were obtained from a local dairy at Tizi-Ouzou, Algeria.
The results showed that increasing of FC lowered titratable acidity and raised organoleptic and physical scores for texture and taste. Titratable acidity increased with increasing NFDM content. NFDM content of 110 g/l gave the highest scores for texture and taste. On the other hand, the scores for taste and syneresis of the fresh made experimental set-type yoghurt contained 25% (v/v) fresh cow milk were higher than those of 100% reconstituted milk and control product (commercial product). Set-type yoghurt produced with 75% reconstituted milk + 25% raw milk was also more appreciated for texture property than the control product (P = .05).
Keywords: Fat content, raw milk, organoleptic and physical properties, yoghurt