PHYSICAL, SENSORY AND FLOW PROPERTIES OF WHEAT STARCH–DAIRY BY‐PRODUCT SPRAY‐DRIED PEKMEZ MIXTURES

Abstract

ABSTRACT Pekmez, also known as a concentrated grape juice, was spray dried in a laboratory‐type pilot drying unit to obtain pekmez powder (PP). The flow characteristics of PP, wheat starch (WS) and some dairy by‐products (whey powder, skim milk powder, calcium caseinate and sodium caseinate) systems as binary and ternary mixtures were studied. The empirical power law model fitted the apparent viscosity–rotational speed data. PP–dairy by‐product and WS–dairy by‐product mixed solutions exhibited a shear‐thinning behavior at 21C with flow behavior index (n) values of 0.86 ≤ n ≤ 0.92 and 0.06 ≤ n ≤ 0.27, respectively. WS–dairy by‐product mixed solutions showed high shear‐thinning behavior with the highest consistency index (k = 25,425–180,599 mPa·sn). However, PP–WS and PP–WS–dairy by‐product mixed solutions at the same temperature exhibited the shear‐thickening behavior with flow behavior index (n) values of 1.05 ≤ n ≤ 1.18.PRACTICAL APPLICATIONSPekmez has become popular as a healthy food product; therefore, its rheologic properties were extensively studied by some researchers. However, pekmez powder (PP) is a new product and has not been produced yet in the food industry. Spray drying of foods has been spread recently in almost all food industry branches because it provides some advantages such as extending the shelf life, storage stability, decreasing the storage costs of the food products, etc. For this reason, production technology is first developed; PP is produced and studied in this study. There is no published data informing the rheologic, physical and sensory properties of pekmez or PP as binary and ternary mixtures with other components such as wheat starch (WS) and any dairy by‐product. The purpose of this study was mainly to characterize the rheologic behavior of the PP–WS–dairy by‐product mixed solutions and determine their physical and sensory properties.