The Development of a Lexicon for Frozen Vegetable Soybeans and Effect of Blanching Time on Sensory and Quality Parameters of Vegetable Soybeans during Frozen Storage
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Date
2005-05-04
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Abstract
American vegetable soybean consumption is limited but potential for increased markets based on increased U.S. production is high. Interest in soy foods has risen, fueled by research proving health benefits correlated with soy consumption. The vegetable soybean (Glycine max. (L.) Merrill) is a specialty soybean harvested when the seeds are immature. Due to the narrow window of time available to harvest this crop, freezing is essential for year-round availability of vegetable soybeans. Investigation into vegetable soybean cultivation and processing in the U.S. is ongoing. A flavor lexicon, a set of terms which identify and define the associated aromatic, tastes and feeling factors of a product, for frozen vegetable soybeans was created. This lexicon will provide a standard flavor language for vegetable soybean producers and researchers. A representative sample of commercial frozen vegetable soybean samples was collected. The frozen vegetable soybean lexicon was developed by a 12 member panel of flavor and soybean specialists. Intensity ratings, based on the Sensory Spectrum® scaling method were given to all lexical terms. Food and chemical references, which exemplified the lexicon descriptors were generated and evaluated by the panel. Frozen vegetable soybean flavor was described by 8 aromatics, 3 feeling factors and the basic tastes. In the subsequent months a highly trained descriptive panel validated the lexical language and intensity scores.
Quality concerns related to vegetable soybeans require harvest to be carried out quickly, dictating that the product be frozen for year round availability. Enzyme inactivation by blanching is needed to maintain nutritional and sensory quality of vegetable soybeans during storage. This research objective was to determine the optimal blanching time prior to frozen storage. Vegetable soybeans (Mojo Green var.) were harvested 119 days after planting. Soybean pods were water blanched (100 °C) for 30, 60, 90, 120 and 180 seconds in duplicate and cooled in ice water. One half of each treatment was shelled and the other half remained in-pod. Samples of both types were packed in plastic bags and stored at -24 ° C. Samples were evaluated after 0, 2, 4, 8, 12, 16, 30, 40 and 52 weeks. Analysis consisted of lipoxygenase activity, descriptive sensory analysis, Hunter L-a-b color, texture, and ascorbic acid. Blanching times of 60 seconds or greater were sufficient to inactivate lipoxygenase. Descriptive sensory analysis showed that off-flavor production was enhanced at blanching times less than 60 seconds and that blanching time was directly related to the development of cooked bean and brothy flavor and umami feeling factor. Texture analysis revealed that blanching time was inversely related to bean firmness. Optimal color retention was achieved in 30 to 90 second blanched shelled soybeans and 30 to 120 second blanched soybeans in-pods. The highest ascorbic acid retention was found in shelled soybeans blanched for 60 to 120 seconds, and in-pod soybeans blanched for 60 to 90 seconds. The results indicated that the shortest acceptable blanching time (60 seconds) with respect to lipoxygenase inactivation also yielded acceptable soybean flavor, crisp texture, green color and highest ascorbic acid retention during frozen storage.
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Keywords
lexicon, storage analysis, freezing, blanching, Vegetable soybeans, process optimization
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Degree
MS
Discipline
Food Science
