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The influence of an alternative chemical pretreatment on dehydration and rehydration of an Italian ecotype pumpkin was investigated. The pretreatment consisted of soaking the slices in a diluted solution of trehalose, sucrose and NaCl. Hot air-drying was performed in a convective dryer at temperatures of 55, 60, 65 and 70°C. Samples treated prior to drying showed a shorter (about 1/4) drying time, less volume shrinkage and colour changes, but showed higher rehydration capacity compared to untreated ones, especially in the range 55-65°C. Moreover, the pretreatment was effective in retention of total phenolic content and antioxidant activity. The Midilli model was the most appropriate for describing drying behaviour, while the Weibull model for rehydration. [ABSTRACT FROM AUTHOR]

The kinetics of carotenoid and color degradation, as well as furosine formation, were investigated in apricot fruits during convective heating at 50, 60 and 70 °C. Degradation of carotenoids and color, expressed as total color difference (TCD), followed a first and zero order kinetic, respectively. The activation energy (Ea) for carotenoids degradation ranged from 73.7 kJ/mol for 13- cis -β-carotene to 120.7 kJ/mol for lutein, being about 91 kJ/mol for all- trans -β-carotene. Violaxanthin and anteraxanthin were the most susceptible to thermal treatment. The furosine evolution was fitted at zero order kinetic model. The Ea for furosine formation was found to be 83.3 kJ/mol and the Q 10 (temperature coefficient) varied from 1.59 to 4.14 at the temperature ranges 50–60 °C and 60–70 °C, respectively. [ABSTRACT FROM AUTHOR]

Grape drying is a slow and energy intensive process because the waxy peel has low permeability to moisture. Therefore, peel chemical and physical pretreatments are considered before drying in order to facilitate water diffusion. However, they cause heterogeneity in the waxes removal and problems during shelf-life. In this paper an alternative abrasive pretreatment of grape peel, for enhancing the drying rate and preserving the samples, was applied to Red Globe grapes. Convective drying experiments were carried out at 40–70 °C and at 2.3 ms −1 air velocity. The effect of wax abrasive pretreatment on the drying kinetics and quality parameters of raisins was investigated. The results were compared with those of samples pretreated by dipping in alkaline ethyl oleate solution and untreated grapes. All the dried samples are darker than fresh one and shrunked. The samples pretreated by peel abrasion and dried at 50 °C showed the lowest color changes, less shrinkage and the best rehydration capacity. The drying kinetics and shrinkage curves were also analyzed using some commonly available empirical models. [ABSTRACT FROM AUTHOR]

Abstract: A microwave based system was developed for drying of apple slices while on-line controlling their temperatures. An infrared thermography assisted control system allowed to realize temperature control by detecting the instantaneous maximum temperature among the samples under test instead of a chosen slice. The effectiveness of the system at hand in realizing temperature control both in space and in time was proven for three temperatures: 55, 65 and 75°C. Temperature fluctuations became larger both with time increasing and with rising temperature levels thus causing a negative impact on dried fruit quality. In fact apples slices dried at 75°C by microwave showed L ∗ (lightness) and white index (WI) values significantly lower (p <0.05), when compared to the fresh samples and to the apples dried by hot air. To overcome such behaviour a mode stirrer was introduced resulting in halving the temperature spatial oscillations of sample slices. [Copyright &y& Elsevier]