INCORPORATION OF FRUIT POMACE IN DIRECT EXPANDED EXTRUDED FOODS

Siyuan Wang

Fruit and vegetable pomace has been considered as a fiber-rich ingredient that can be used in direct expanded extrudates. High level of pomace inclusion usually leads to undesired textures of extrudates. Therefore, the objective of this research was to investigate the factors causing negative impacts of pomace on expansion and find processing solutions to effectively incorporate it into extrudates at higher levels without losing expansion. Impacts of pomace physicochemical properties, inclusion level, and extrusion conditions on expansion of corn starch-based extrudates were studied. Correlation analysis showed that total dietary fiber, insoluble dietary fiber, and crystallinity of fruit pomace had a negative correlation to expansion ratio (ER) of extrudates (p < 0.01). However, soluble fiber and sugar had positive correlation to ER at 30% pomace level (p < 0.05). Physical modification of cherry pomace, which included reduction of pomace particle size by milling was evaluated to improve ER of extrudates. Effect of pomace particle size, pomace inclusion level, and extrusion conditions on expansion and microstructural characteristics of extrudates were investigated. ER increased at 5% pomace level, compared with control but decreased at 15% inclusion (p < 0.05). Particle size significantly affected ER (p < 0.05), with smaller particle size resulting in increased ER at all pomace levels. Cranberry pomace (CBP) was subjected to mild alkaline hydrogen peroxide modification to evaluate its impacts on improving expansion of extrudates at high inclusion levels. Modified CBP helped to increase expansion of extrudates at 30% inclusion (p < 0.05). Extrudates with modified CBP had structures with more cell numbers, smaller cell size, and more uniform cell distribution compared with non-modified CBP. Results from this research showed the presence of positive active interactions between fruit pomace components and corn starch that could help increase or maintain expansion of extrudates during extrusion. This research helped to design starch extrudates with higher fiber incorporation, using fruit and vegetable pomace and with better expansion. Further research is needed to identify the specific positive interactions between pomace components and starches, which can lead to strategies for effective incorporation of pomace into starch extrudates without losing quality attributes desired by consumers.

INCORPORATION OF FRUIT POMACE IN DIRECT EXPANDED EXTRUDED FOODS

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