Evaluation of quality parameters of sumac berries and sumac concentrate

When sumac (Rhus coriaria) berries were leached in water, the juice obtained had a bright red color with a characteristic sour taste. To prevent microbial and chemical deteriorations, this juice was concentrated using a batch-type rotary, and a rising film evaporator. The quality parameters, such as color, composition, and moisture sorption of both sumac berries and the resulting concentrate were then evaluated with respect to age, storing conditions, leaching temperature, and geographical type of berries. The variation of the rheological characteristics and the density of the concentrate with temperature, and total soluble solids (TSS) were also evaluated. The composition, and thus the color, and sorption properties of both the berries and the concentrate were observed to be highly temperature-dependent. As expected, the rate of extraction of TSS of sumac berries increased while the density and viscosity decreased with temperature. At relatively low TSS (X?60 brix), sumac concentrate showed Newtonian behavior, while samples with higher TSS (X?70 brix) exhibited a slight yield stress (?0=3.05 pa) with shear-thinning behavior (n=0.85) at the lowest temperature (20 oC) studied. Zero and first order kinetics were applied to Hunter-Lab color parameters of the concentrate. The activation energy of the change of L value for 10% TSS was found to be 26.97 kj/mol whereas for 37% TSS it was 36.67 kj/mol. ii Total phenolic content (TPC) of the concentrate were determined as a function of the type, age, and processing of the berries. Samples prepared from one year old and two years old berries were observed to contain 0.28, and 0.25 mg gallic acid ?L respectively. Non-processed new crop sumac extract had the highest quantity of anthocyanin (614 mg/l) as compared with 342 mg/L for the processed (concentrated in a rising film evaporator) sample. The polymeric color of the concentrate was observed to increase with the age of berries. This means that, on standing under ambient conditions, sumac berries undergo some reactions leading to the intensification of the polymeric color. The main organic acids found in sumac concentrate were identified as malic and gallic acids. Although a slight variation with respect to the geographic origin was observed, on average, malic and gallic acids, constitute 42.7 % and 10.2 % of the whole organic acids present in sumac berries respectively. Key words: Sumac berries, sumac concentrate, quality parameters, Rhus coriaria.