Date of Award

2000

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

School of Nutrition and Food Sciences

First Advisor

Paul W. Wilson

Second Advisor

Douglas L. Park

Abstract

The comparative efficacy and quality characterization of juice by six extraction methods utilizing either frozen or fresh 'Texas Star' mayhaw (Crataegus opaca Hook. and Arn.) fruit obtained from the 1998 and 1999 crop season were conducted according to temperature (cold-press or hot-press extraction) and fruit pulp pretreatment (whole or pulverized fruit with or without pectolytic enzyme). Extraction methods were steam extraction using whole fruit without added pulp juice (SE); steam extraction using whole fruit with added pulp juice (SEP); cold-press extraction using whole fruit (CPE); cold-press extraction using finely macerated fruit pulp (CPEG); hot-press extraction using finely macerated fruit pulp (HPEG), and hotpress extraction in combination with a pectolytic enzyme pretreatment (ENZ). Maceration of fruit, plus the application of heat to the fruit pulp prior to expression, had a significant influence in juice extraction efficacy for both fresh and frozen fruit. Application of a commercial pectolytic enzyme (0.20% w/w) to mayhaw pulp mash (1 hr at 32°C) increased extraction efficacy by of 21%. ENZ-fresh extraction had the highest percent total soluble solids (TSS) at 8.1% and was 7% more efficient in recovery as compared to ENZ-frozen extraction (7.6%). The fructose to glucose (F/G) ratio of juice recovered from all extraction methods utilizing either fresh or frozen fruit was greater than 2.0. In total sugars (fresh or frozen) there were no significant differences found between hot or cold-press extracted juices or the use of whole or macerated fruit. The CPEG extraction method using fresh fruit had a CIE b* color-value (2.55) that was significantly higher than all other methods of juice extraction. There were no significant differences in juice pH, which ranged from 2.9 to 3.1, between either fresh or frozen extracted juices. Juice from one cultivar of muscadine grape (Vitis rotundifolia Michx.) 'Carlos' (bronze-skinned) was mixed with varying levels of juice from 'Texas Star' mayhaw. Panelists' mean scores collectively were favorable of either 60:40 or 40:60 mayhaw:muscadine juice blends and "Taste" contributed the most to overall acceptance.

ISBN

9780599906310

Pages

154

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