Granny Smith apples were processed into juices and concentrates from fruits which had been stored at 1°C for three months (short-term, ST) and nine months (long-term, LT). Total soluble proteins decreased with storage time of fruits. Juices processed from ST fruits were more resistant to haze formation (heat stability test) than those processed from LT fruits. For juices processed from ST apples, haze formation was related to proteins in the MW range of 21,000 to 31,000 daltons. For juices processed from LT apples, haze formation was not only related to proteins but also to other components in the juices. Fining was recommended to prevent haze and sediment formation.

The effect of modifying the structural properties of a purified cellulose on its subsequent digestion in the rat was determined. The three structurally unique types of cellulose used in the study were a commercial microcrystalline cellulose, a ball-milled cellulose, and an acid-swollen cellulose. The ball-milled cellulose and the acid-swollen cellulose were prepared from the microcrystalline cellulose starting material. Differences in structure between the types of cellulose were determined by X-ray diffraction measurements and by analysis of their in vitro enzymatic saccharification. The extent of fermentation of each type of cellulose within the rat intestinal tract was determined. Each of the three types of cellulose had a unique structure with respect to its measured crystallinity index and its rate of degradation in vitro by cellulase enzymes. The measured in vivo digestion coefficient for microcrystalline, ball-milled, and acid-swollen cellulose was 8.8, 12.2 and 20.3%, respectively. This represents a significant difference (P less than 0.05) in the extent of fermentation of the different structural types of cellulose within the rat intestine. The results demonstrate that modifying the structural properties of dietary cellulose can affect in vivo response.

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d'Anjou, Cornice, and Bartlett pears were processed into clarified juices from hard green and soft ripened fruits. Processing trials with and without SOz were conducted. Effects of variety, maturity and processing on browning, turbidity, proteins, and stability were investigated. Browning increased with heat treatment, and was reduced by processing with SOz. Total soluble protein content increased with fruit maturity and processing with SO*. Protein fractions from a clarifying enzyme preparation (mainly arabinase and amylase) with MW in the range of 64,000-92,000 and containing glycoproteins were not removed by fining/clarification. They contributed to protein instability in the clarified pear juices, but could be removed by heat treatment (pasteurization) prior to final filtration and bottling. Our results indicate some enzymes added for clarification during processing may contribute to post-clarification haze and sediment formation.