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Optimization of the solid-liquid extraction conditions for trans-resveratrol, trans--viniferin, ferulic acid, and total phenolics from milled grape canes has been investigated. The temperature and ethanol concentration were found to be major process variables for all responses, whereas the solvent to solid ratio was found not to be significant for any of the responses studied. The yields of trans-resveratrol, trans--viniferin, and total phenolics increased with increasing temperature. Maximum yields of trans-resveratrol (4.25 mg/g dw), trans--viniferin (2.03 mg/g), and total phenolics (9.28 mg/g dw) were predicted from the combination of a moderate ethanol concentration (50-70%) and the highest temperature (83.6 degrees C), whereas an ethanol concentration of 35% at the lowest temperature studied (16.4 degrees C) was optimal for the extraction of ferulic acid (1.05 mg/g dw). Effective diffusivity values of resveratrol in the solid phase, D eff for different extraction conditions, were calculated by fitting the experimental results to a model derived from the Fick's second law. Effective diffusivity of resveratrol in the solid phase varied from 3.1 x 10 (-13) to 26.6 x 10 (-13) m (2) s (-1) with changing extraction conditions. The increase in effective diffusivity of resveratrol was observed with increasing temperature, and the highest predicted level was obtained when using 54% ethanol/water mixture at 83.6 degrees C. The increase in ethanol concentration exhibited the favorable effect up to 50-55%, thereafter effective diffusivity decreased with a further increase in concentration.

Trans-resveratrol and trans-ε-viniferin were extracted from milled grape canes using pressurized lowpolarity water. The effects of temperature were significant for both compounds (p≤0.05): extraction at 160°C resulted in a 40% loss of trans-resveratrol compared to 95°C while reduction of trans-ε-viniferin at both temperatures remained at 30%. Increasing ethanol concentration from 0% to 25% increased the extraction of total phenolics and trans-ε-viniferin by 44% and 489%, respectively. Solvent flow rate also influenced trans-ε-viniferin extraction. Antioxidant activity showed a strong correlation with total phenolic content of the extracts, and the two target phenolic compounds. Except for the modifier concentration, the extraction parameters studied were not statistically significant with respect to the antioxidant activity of extracts (p> 0.05). Effective diffusivities of trans-resveratrol multiplied from 3.3×10 −11 to 10.4×10 −11 m 2 /s by three times with increasing temperature. The modified Gompertz equation satisfactorily explained the extraction of the stilbenes investigated. Nomenclature CSolute concentration at any location in the particle at time t, mg/mL C i Initial solute concentration, mg/mL D eff Effective diffusivity, m 2 /s D o Initial diffusivity, m 2 /s t Extraction time, s r Radial distance coordinate from centre of spherical particle, m R Average particle radius, m M t Total amount of solute removed from grape cane at time t, mg/g dw M ∞ Maximum amount of solute extracted at equilibrium, mg/g dw y Total amount of phenolic compound extracted from grape cane sample at time t, mg/g dw y ∞Maximum amount of phenolic compound extractable at equilibrium, mg/g dw m Maximum extraction rate defined as the tangent in the inflection point, mg/(g·min) eIrrational constant (exp(1)=2.718…) λTime period, min E a Activation energy for diffusion, kJ/mol R Universal gas constant, kJ/(mol·K) T Absolute temperature, K

Solid-liquid extraction of resveratrol and viniferin from grape cane samples was described by using first-order kinetic model, Peleg's model, two-site kinetic model and modified Gompertz equation. Goodness of fits of the models were evaluated by comparing the adjusted determination coefficient and root mean square error and mean percentage error values. Although the two-site kinetic model with four parameters described the data better, Peleg's model, with only two parameters, could explain the data with a slight loss of goodness of fit. The modified Gompertz equation showed the worst performance for describing the solid-liquid extraction of stilbenes. PRACTICAL APPLICATIONSThe present study introduces the comparison of well-known models applied to explain extraction kinetic of stilbene compounds of grape cane and to determine the best model with its justifications. Mathematical models provide information about the system and/or process to which they are applied. In design and/or process application stages, any information about that process and/or system has crucial importance because in the decision stages, this know-how helps the designers and researchers find the best design parameters and the most effective process conditions to optimize purposes. Mathematical models are accepted as the most economical ways for these purposes. bs_bs_banner Journal of Food Process Engineering

Postharvest storage conditions of rowanberry (Sorbus aucuparia) fruits were investigated. The influences of temperature and storage time on total phenolic content were observed. Both variables affected phenolic content of rowanberries, and their total phenolic contents significantly reduced during the 20-day storage at 4 and 22C. The loss of total phenolic was found to be almost 50% of its initial amount (3,619.8 mg/kg fresh weight [fw]) at 22C, which was higher than occurred loss (30%) at 4C. An investigation of rowanberry flavonoids showed the presence of rutin, quercetin-3-glucoside and quercetin-3-D-galactoside (Q3DG). Quantitative analysis of berry flavonoids showed Q3DG as a major compound, being 24.55 mg/kg fw. The highest reduction (86% of its initial amount) was also seen in that compound level compared with other ones. Degradation kinetics of flavonoids was studied at 22C over 16 days of storage. Checking of model adequacies indicated that their reductions followed a first-order kinetic. PRACTICAL APPLICATIONSPostharvest storage has been taken, increasing the interest of scientists because of various reasons, one of which is explained next. The presented results indicated the direct and/or indirect influence of storage conditions on the quality of berries, implying that whoever is planning to store plant and/or plant origin food products in a refrigerator or at room temperature should consider the conditions and their possible effects on the quality parameters from the aspects of economics and nutritional properties of products. In the present study, the stability of an important bioactive group, phenolics, in rowanberries and the influences of environmental conditions were examined, and additionally, degradation kinetics of major phenolic group, flavonoids, was analyzed. The results are valuable and helpful for the evaluation of the postharvest storage and its effect on rowanberries. Introduced model may be helpful for the prediction of storage time required for the degradation of phenolics up to the acceptable limit.

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The results presented indicated that the proposed cooking method is useful to control final oil content of fried carrot slices, so indirectly limiting the daily calorie intake by consumers without spectacular losses in quality attributes. © 2016 Society of Chemical Industry.