Effect of microwave power, air velocity and temperature on the final drying of osmotically dehydrated bananas

This paper reports on a study of the final stage of microwave-hot air drying of osmotically dehydrated bananas, focusing on the effects of microwave power, air temperature and air velocity on drying kinetics and product quality, evaluated in terms of colour, apparent volume and porosity. The drying process was divided into three periods: phase I (760 W; 2 kg(moisture)/kg(dry matter)); phase II (380 W; 0.67 k9(moisture)/k9(dry matter)), and phase III (0 W, 76 W, 150 W or 230 W up to the final sample moisture of 0.17 kg(water)/kg(d m)). Three conditions for the hot air were tested: 50 degrees C and 3.3 m/s; 70 degrees C and 3.3 m/s; 70 degrees C and 5.7 m/s. The results show that increasing the microwave power in phase III increased the drying rate, thus making the drying time shorter. However, higher microwave power also caused temperature runaway leading to charring on the dried product. Air flow cools the product surface and improves product quality by reducing charring. (c) 2006 Elsevier Ltd. All rights reserved.811798

Microwave convective drying of plant foods at constant and variable microwave power

Microwave convective drying of plant foods is a promising process due to the shorter drying time and better product quality. High microwave power decreases the drying time but causes charring of the product. In this work, microwave drying under constant and variable microwave power were compared. Temperature-sensitive products, such as plant foods, are especially affected by microwave power during the final drying period. Therefore, drying at variable microwave power was found to be a more suitable drying process. Air (temperature and velocity) has an important role during microwave drying, not only as carrier of evaporated moisture but also as it contributes to a more homogeneous and faster drying.25418581149115

Metabolic engineering of lactic acid bacteria for the production of nutraceuticals

Lactic acid bacteria display a relatively simple and well-described metabolism where the sugar source is converted mainly to lactic acid. Here we will shortly describe metabolic engineering strategies on the level of sugar metabolism, that lead to either the efficient re-routing of the lactococcal sugar metabolism to nutritional end-products other than lactic acid such as L-alanine, several low-calorie sugars and oligosaccharides or to enhancement of sugar metabolism for complete removal of (undesirable) sugars from food materials. Moreover, we will review current metabolic engineering approaches that aim at increasing the flux through complex biosynthetic pathways, leading to the production of the B-vitamins folate and riboflavin. An overview of these metabolic engineering activities can be found on the website of the Nutra Cells 5th Framework EU-project (www.nutracells.com). Finally, the impact of the developments in the area of genomics and corresponding high-throughput technologies on nutraceutical production will be discusse