SEASONAL-CHANGES IN THE COMPOSITION AND PROPERTIES OF A HIGH DIETARY FIBER POWDER FROM GRAPEFRUIT PEEL

Seasonal changes in composition and properties of a high dietary fibre product from grapefruit peel were studied. Total dietary fibre decrea sed in January as compared to September (586-686 g kg(-1)). Main const ituents from soluble fibre were: uronic acids (172-233 g kg(-1)), arab inose (13-41 g kg(-1)), galactose (4-11 g kg(-1)), glucose (5-10 g kg( -1)) and xylose (2-3 g kg(-1)). Insoluble dietary fibre (385-392 g kg( -1)) did not significantly change during the season. Its main constitu ents were: Klason lignin (29-37 g kg(-1)), uronic acids (33-70 g kg(-1 )) and neutral sugars: glucose (149-196 g kg(-1)), mannose (45-50 g kg (-1)), xylose (25-38 g kg(-1)), galactose (20-22 g kg(-1)) and arabino se (16-45 g kg(-1)). Total neutral sugars from dietary fibre decreased over the harvest period (315-383 g kg(-1)) and an inverse trend was o bserved in total free-sugars from samples (49-85 g kg(-1)). Both, wate r holding capacity (7.0-9.3 g water g(-1) dry sample) and glucose reta rdation index (7.0-25.3%) decreased from early stages in fruit develop ment until late in the harvest season. Seasonal changes in grapefruit peel should be taken into account, in order to standardise the quality of rich fibre products.