Rheological Characteristics of Fresh and Freeze-Dried Reconstituted Juices Obtained from Some Non-Traditional Fruits

Abstract

This study aimed to evaluate rheological characteristics of juices and freeze dried for acerola, annona and cactus at 25°were the relationship between the applied shear rates and the corresponding shear stress response are not linear indicating the non-Newtonian behavior of the juices obtained from acerola, annona, and cactus fruits. The magnitude of the obtained shear stress values varied according to the type of fruit and its composition Maximum shear stress response at shear rate of 145.8s-1were122.97 and 59.87 Dynes/cm2for juices obtained from acerola and annona respectively. On other side, the juices of yellow and red cactus fruit recorded lower shear stress values at the same shear rate145, 8s-1, being 27, 68 and 30, 75 Dynes/cm2, respectively. According to power law equation model applied parameters are given the n-value of tested juices was in the range of 0.222 to 0.5203 indicating the pseudoplastic behavior of the tested fruit juices. The highest values of consistency coefficient (K-value) was recorded for acerola juice (14.70 Dynes.S-1 /cm2) the lowest values was recorded for red cactus after enzyme (4.766 Dynes.S-1 /cm2). The highest values of R2 were recorded for yellow cactus after enzyme (0.998) the lowest values were recorded for annona juice (0.868). The rheological parameters of the reconstituted juices, the n-value as in the range of 0.562 to 0.6955, being higher than their corresponding n-values of the fresh juices. The lowest values were recorded for red cactus juice reconstituted. ). The highest values of R2 were recorded for yellow cactus was (0.9907) but the lowest values were recorded for red cactus juice reconstituted. The highest values of consistency coefficient (K-value) was recorded for yellow cactus (2.733 Dynes.S-1 /cm2), the lowest values was recorded for Annona (1.030Dynes.S-1 /cm2).