44C-13 |
Carotene changes in carrots, sweet potatoes and spinach as affected by rotary and still retort processes |
C. R. BROWNMILLER, Food Science, University of Arkansas, 2650 N. Young Avenue, Fayetteville, AR 72704 and L. R. Howard. In conventional still retort processing of carotene-rich vegetables, much provitamin A activity can be lost by conversion of all-trans-carotenes to steroisomers, due to the harsh thermal process required to achieve commercial sterility. Agitating retorts may reduce process time by faster and more uniform heat penetration throughout the product. Thus, agitated processing may result in less thermal stress, allowing for greater retention of provitamin A carotenes in canned vegetables. Our objective was to determine carotene changes in canned sweet potatoes, carrots and spinach receiving heat processes of comparable lethality in still and agitating retorts. Fresh carrots, sweet potatoes and spinach were blanched and thermally processed in still and agitating retorts to obtain comparable lethality (Fo=6) using commercial conditions. Carotenoids were extracted and analyzed by HPLC using a polymeric C30 column. Isomers of all cis standards of a-carotene, b-carotene and lutein were prepared by iodine catalyzed isomerization. Carotenoids were identified and quantified by retention times and absorption spectra as compared to external standards. Isomers were quantified as equivalents of their all-trans forms. Rotary processed sweet potatoes contained higher levels of all trans a and b-carotene, and greater provitamin A activity than still processed samples. No differences in carotene content or provitamin activities were observed between rotary and still processed carrots. Still processed spinach contained greater provitamin A activity than rotary processed samples, but no differences in levels of all-trans b-carotene, all-trans lutein or zeaxanthin were observed.
Rotary processing improved carotenoid retention of sweet potatoes, had no effect on carotenoid retention in carrots, and was detrimental to carotenoid retention in spinach, relative to still processing. Differences in carotenoid retention among rotary and still processed vegetables may be attributed to differences in piece size and product surface to volume ratio.
Session 44C, Fruit & Vegetable Products: Chemistry
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