CHEMICAL, NUTRITIVE AND SENSORY CHARACTERISTICS OF TOMATOES BEFORE AND AFTER CONVENTIONAL AND MICROWAVE BLANCHING AND DURING FROZEN STORAGE

Effects of radiofrequency blanching on lipoxygenase inactivation, physicochemical properties of sweet corn (Zea mays L.), and its correlation with cell morphology

This study investigated the effects of radiofrequency (RF) and boiling-water (BW) blanching on lipoxygenase (LOX) activity, physicochemical properties, and changes in the cellular morphology of sweet corn kernels. First, a speed-adjustable device was introduced to rotate the sample for improving heating uniformity. Then, the maximum RF heating rate and uniform temperature distribution of samples were obtained under 160 mm electrode gap, 120 g sample weight, and 14 r/min rotating speed. With increased RF heating temperature ranging from 50 °C to 80 °C, the residual activity of LOX significantly decreased to 4.68%. Samples blanched by RF treatment maintained better color, texture, and nutrient content than those by BW when similar levels of enzyme inactivation were achieved. Micrographs also showed the cells were increasingly damaged with increased RF heating temperature, whereas the cells were damaged much more severely when treated with BW. Besides, microscopic destruction of cells also explains the changes in physicochemical properties.

Advanced preservation methods and nutrient retention in fruits and vegetables

Despite the recommendations of international health organizations and scientific research carried out around the world, consumers do not take in sufficient quantities of healthy fruit and vegetable products. The use of new, 'advanced' preservation methods creates a unique opportunity for food manufacturers to retain nutrient content similar to that found in fresh fruits and vegetables. This review presents a summary of the published literature regarding the potential of high-pressure and microwave preservation, the most studied of the 'advanced' processes, to retain the natural vitamin A, B, C, phenolic, mineral and fiber content in fruits and vegetables at the time of harvest. Comparisons are made with more traditional preservation methods that utilize thermal processing. Case studies on specific commodities which have received the most attention are highlighted; these include apples, carrots, oranges, tomatoes and spinach. In addition to summarizing the literature, the review includes a discussion of postharvest losses in general and factors affecting nutrient losses in fruits and vegetables. Recommendations are made for future research required to evaluate these advanced process methods.