Andrija Pozderović

Influence of processing parameters on permeate flow and retention of aroma and phenolic compounds in chokeberry juice concentrated by reverse osmosis

ABSTRACT Reverse osmosis (RO) concentration of chokeberry juice, a rich source of polyphenols, at three different pressures (45, 50 and 55 bar) and two temperature regimes (with cooling and without cooling of the retentate) was studied. Concentration was carried out on a laboratory membrane unit with plates and frames on composite Alfa Laval membranes RO98pHt. Juice was concentrated till 24.9% of total soluble solids content (TSSC) . The permeate flow highly depended on processing parameters and varied from 15.19 ± 3.22 L/m2h at the beginning to 8.00 ± 2.21 L/m2h at the end of processes. Total phenolic compounds (4 anthocyanins, 2 flavonols and 2 phenolic acids) were determined by high performance liquid chromatography (HPLC). Twenty four volatile compounds were identified by gas chromatography with mass spectrometry (GC-MS) in chokeberry juice and concentrates. Processes at 50 and 55 bar with cooling proved to be the best in terms of chokeberry aroma, antioxidant activity and total phenolic compounds retention.

Influence of Sugars, Modified Starches and Hydrocolloids Addition on Colour and Thermal Properties of Raspberry Cream Fillings

Abstract This paper deals with the influence of the addition of sugars (sucrose, fructose and trehalose), modified starches (tapioca or waxy maize starch) and hydrocolloids (karaya or guar gum) on colour and thermal properties of raspberry cream fillings. In addition, the influence of the above-mentioned additives on the colour and thermal properties of raspberry cream fillings stored at room temperature over a period of 8 and 16 months was investigated. Results showed that the highest anthocyanin content and total phenolic content were detected in raspberry cream filling prepared with sucrose and trehalose in combination with guar gum. During storage, after 8 and 16 months at room temperature, anthocyanin content and total phenolic content decreased. Results also showed that the kind of sugar and added modified starches or hydrocolloids influenced the thermal properties of cream fillings. During storage, a decrease was observed in both freezing temperature as well as enthalpy of cream fillings.