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Rheological properties of sour cherry juice were determined by a Controlled Stress Rheometer. Sour cherry juice with different solid contents (40, 45, 50, 55, 60, 65, 68.5 and 70 Brix) was prepared using a rotary evaporator after squeezing and filtration of sour cherries. The rheological behavior of these concentrates was studied in the temperature range of 5, 10, 20, 30, 40, and 50°C. Sour cherry juice was found to exhibit Newtonian behavior. The effect of temperature on viscosity can be described by means of an Arrhenius equation. Activation energies appeared in the range of 22.44-73.49 kJ/mol with increasing concentration. To study effect of concentration on the viscosity, power-law and exponential equations were used. Finally, two equation describing the combined effect of temperature and soluble solids content on the viscosity of concentrated sour cherry juice were obtained.

Mint leaves were dried by three different types of dryers, namely; tray, freeze and distributed (indirect)-type solar dryer. Sorption isotherms of fresh, solar, tray and freeze dried mint were determined at temperatures of 15 °C, 25 °C and 35 °C over a range of relative humidities (10-90%). The effect of drying method on the water sorption isotherms of dried mint samples was evaluated. Experimental data were used to determine the best models for predicting the moisture sorption content of mint. Among nine sorption models tested, Peleg, GAB, Lewicki and modified Mizrahi equations gave the best fit to experimental data. The sorption data were analyzed for determination of monolayer moisture content, density of sorbed water, number of adsorbed monolayers, percent bound water, and surface area of adsorbance. The experimental data were also used to determine some thermodynamic properties of mint.

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BACKGROUND: Spices are used in different types of foods to improve flavours and are well known for their antioxidant properties. The objective of this study was to determine the effects of rosemary and Hibiscus sabdariffa on the quality attributes of kavurma, a cooked meat product. RESULTS: pH values of samples remained constant (P > 0.05) at about 6.35 during the cooking period, and addition of H. sabdariffa, rosemary or butylated hydroxytoluene (BHT) did not significantly affect pH values (P > 0.05). However, addition of antioxidants decreased (P < 0.05) thiobarbituric acid-reactive substance (TBARS) values, the highest values being observed in control samples. Lightness (Hunter L) values of control samples increased (P < 0.05) from 28.79 to 37.91 during the first 20 min of cooking. Hunter a and b values were significantly affected (P < 0.05) by process time and addition of antioxidants. Addition of BHT, rosemary or H. sabdariffa did not affect the overall sensory attributes of kavurma during the cooking process. CONCLUSION: Colour values changed during the cooking process, mainly as a result of browning reactions. Addition of rosemary or H. sabdariffa enhanced the colour attributes of kavurma during cooking. Rosemary and H. sabdariffa could be used to modify the quality characteristics and obtain kavurma with a low TBARS value and probably a longer shelf-life.

This study showed that nanoencapsulation by electrospinning is an effective way to stabilize carotenoids, which is promising for their use in food processing. © 2018 Society of Chemical Industry.

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