The effects of ultra‐high pressure (UHP) on 25 starches were characterized via microscopy and DSC. Furthermore, the swelling behaviour, digestibility, paste viscosity and gel formation was determined. With few exceptions B‐starches were shown to be more pressure resistant than A‐ and C‐type starches. The pressure range in which the gelatinization occurs is typical for the corresponding starch. Only some starches (e.g. waxy corn starch) show the extensive swelling and almost complete desintegration of the granules, which usually is observed after a heat gelatinization. Typical for a UHP‐gelatinization is, that most starches show very little swelling and maintain their granular character. These starches develope very little viscosity at normal paste concentrations and form pastes of smooth texture, resp. rigid gels at concentrations above 15%. Due to the limited swelling without any resp. very little solubilization of the amylose obviously the retrogradation occurs within the granules, which probably is a further reason for the quite different paste and gel properties of UHP‐gelatinized starches in comparison to heat gelatinized ones.

High intensity electrical field pulse (0.22 to 1.60 kV/cm) pretreatment was tested to accelerate the osmotic dehydration of carrot. Applied energy in the range of 0.04 to 2.25 kJ/kg, increased cell disintegration index in the range of 0.09 to 0.84 with < 1 °C rise in the product temperature. The effective diffusion coefficients of water and solute, determined using a Fickian diffusion model, increased exponentially with electric field strength according to D = A exp(-B/E). The rise in effective diffusion coefficient may be attributed to an increase in cell wall permeability, facilitating transport of water and solute. Such increase was evidenced by cell disintegration index and softening of product.

loo+--High-pressure pretreated and frozen green beans, carrot dice or potato cubes were fluidized bed dried and compared to untreated, pressuretreated or water-blanched dried samples. Drying rates varied with pretreatments. Freezing resulted in highest drying rates. Pressure-treated and water-blanched samples retained highly acceptable colors. Freezing or hot-water blanching or high-pressure pretreatment, followed by freezing, gave good rehydration. High-pressure treatment resulted in incomplete rehydration but combined with freezing, water uptake was between 2.1 and 4.8 mug. Retention of cell wall structures of frozen samples during drying was presumed responsible for more efficient mass transfer. Texture measurements revealed significant effects of pretreatments. Pressuretreated samples had texture nearest that of the raw material. No major differences in color were observed.

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Summary The impact of different pretreatment methods [high pressure (HP), high‐intensity electric field pulses and freezing], osmotic solutions (sucrose, glucose and salt–sucrose mix) and osmotic conditions (atmospheric pressure, vacuum and ultrasound treatment) on the mass transfer of strawberry halves during osmotic dehydration (OD) and on some physical characteristics (leaching of cell constituents, colour and texture), were investigated. Highest water loss was obtained in samples treated under vacuum, in a salt–sucrose mix or under HP or in a high‐intensity electric field. The increase in solid gain relative to untreated samples was 96–270% for the prefrozen treatment, 40–160% for high pressure and 50–62% for high‐intensity electric field treatments. OD under vacuum and the use of glucose solutions facilitated greater solid gain. Leaching of cell constituents was high in prefrozen samples, leading to greater change in product colour and softer texture compared with other pretreatments. Although OD under ultrasound treatment enhanced mass transfer, its overall influence was not significant (P > 0.05) compared with atmospheric pressure.

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Problem statement: Rice straw has been treated with different chemical (acid, alkali) and physical (subcritical water, ultrasound) methods to convert lignocellulose material to sugar. In addition enzyme treatment of pretreated samples has been applied to improve the conversion of lignocellulose material in sugar. Approach: Sulfuric acid at concentration of 1-9% was applied for acid treatment. For alkali treatment was sodium hydroxide solution at concentration of 1-5% used. Subcritical water treatment carried out at 160°C (5 bar) and 200°C (15 bar) for 10 min. Ultrasound was applied as combination method after acid pretreatment. The condition during ultrasound treatment was 40 W at 50°C and 10 min. Finally the pretreated sample was fermented using Saccharomyces cerevisiae yeast and the amount of produced ethanol was measured. Results: Acid treatment at 121°C, 15 min is an effective pretreatment method for converting lignocellulose to sugar. Up to 21.45% sugar w/w could be measure after acid treatment. Combination of chemical pretreatment and subsequent enzyme treatment increased the sugar yield drastically. Up to 37 and 28% sugar w/w could be achieved for acid and alkali pretreated samples respectively. Subcritical Water (SCW) treatment method is an effective physical method. SCW treatment at 200°C and 10 min followed by enzyme treatment yielded up to 17% sugar w/w. Combination of acid pretreatment with ultrasonic before enzyme treatment increased the conversion of lignocelluloses to sugar. Sugar yield up to 44% w/w after combination of acid and ultrasonic pretreatment and subsequent enzyme treatment could be achieved. Fermentation of pretreated rice straw shown that after 3 days fermentation most of sugar (55-65%) will be converted to bioethanol. The remaining sugar could not be converted in ethanol even after 6 days fermentation. Under these conditions, the maximum ethanol of 1.69% (v/v) was obtained. Conclusion: The combination method of acid pretreatment combined with ultrasound and subsequent enzyme treatment result the highest conversion of lignocelluse in rice straw to sugar and consequently, highest ethanol concentration after 6 days fermentation with S. cerevisae yeast.