In vitro fermentation characteristics of fruit and vegetable juicing wastes using human fecal inoculum are determined by cell wall architecture
Widaningrum, Bernadine M. Flanagan, Barbara A. Williams, Francesca Sonni, Deirdre Mikkelsen, Michael J. Gidley
Abstract
Fruit and vegetable juicing wastes are a promising source of hydrocolloids with potential gut fermentation benefits for applications in foods. The aim of this study was to investigate the fermentation characteristics of juicing wastes from apple, beetroot, carrot, celery, orange and pineapple to characterise fermentation rates, gas production and end-products. All juicing wastes had high dietary fibre content (70–90%) and high water-holding capacity (9–12 g H2O per gram dry matter) consistent with food application potential but had diverse fermentation rates and extents over a 48h period. Apple, carrot and orange waste were well-fermented, beetroot and celery waste were less well fermented and pineapple waste was the least fermented as indicated by gas production and short chain fatty acid concentrations. Variations in fermentability were determined by cell wall architecture more than polymer chemistry. Apple, carrot and orange waste were primarily parenchymal fleshy tissue with loosely packed cell walls and readily fermentable. Beetroot and celery waste had more compact cell walls, while pineapple waste had the most densely packed cell walls and the highest cellulose content. The molecular composition of unfermented material also changed during fermentation, with pectin the fastest fermenting, followed by hemicelluloses such as (arabino)xylan, xyloglucan, and mannan while cellulose was the slowest. The results show the potential for unrefined juicing wastes to provide sustained fermentation throughout the large intestine.