Abstract
The present study was conducted to evaluate the influence of lactose hydrolysis by using two different strategies (by addition of β-galactosidase (HA-LACTASE™) before fermentation of camel milk to get hydrolyzed camel milk as substrate that included three levels of lactose-hydrolyzed milk (LHM) 25, 50 and 90% or together with the starter cultures during fermentation (co-hydrolysis)) on the microbiological, physicochemical and sensory properties of fermented camel during manufacturing and the storage period of 21 days at 5ºC. In general, the results showed a significant (P<0.05) reduction in fermentation time with an increase in the level of lactose hydrolysis. The co-hydrolysis fermented milk exhibited a significant (P<0.05) decrease in the fermentation time (279 min) in comparison to control treatment (452.5 min). After 6 h of the incubation period, the viable cell counts were more outstanding in the co-hydrolysis and LHM 90% fermented milk, about 1 log cycle higher than other treatments. The mean values of pH were a highly significant (P<0.05) dropped in co-hydrolysis and LHM 90% samples and reached to pH 4.6 in 6 hours, whereas the control, LHM 25 and 50% samples reached to the near of the same degree of pH in 8 hours of the fermentation process. Furthermore, the higher amount of exopolysaccharide (EPS) was found in co-hydrolysis fermented milk 262.3 mg/kg followed by LHM 90% 250.3 mg/kg, while control, LHM 25 and 50% treatments had the lowest amount of 178.3, 185.3 and 197.7 mg/kg, respectively. The higher amount of EPS in co-hydrolysis and LHM 90% treatments caused a concomitant increase of the apparent viscosity and a significant (P<0.05) decreased in susceptibility to syneresis in comparison to other treatments. Moreover, the co-hydrolysis fermented camel milk had significantly (P<0.05) higher ratings for all sensory characteristics and more liked than other treatments. Although the LHM 90% samples had a better rheological characteristic, the panelists rated as unacceptable because of the strong sweet taste. Results showed that the simultaneous addition of enzyme and starter together demonstrated to be a satisfactory strategy in making fermented camel milk with high quality in the texture and overall acceptability beside its beneficial properties as a functional dairy product.
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