Comparison of steam and water processing on physical, chemical, and nutritive characteristics of southern peas (Vigna unguiculata (L.) Walp)

The objective of this investigation was to determine the effects of processing with steam (103.5 Pascal) on the physical, chemical, and nutritive values of two maturities of southern peas, as compared to peas processed in water. The moisture content of the steam-processed peas remained constant, while the water-processed peas increased in moisture content. Processing had little or no effect on the other proximate components. Processing had no effect on the amino acid profile. The chemical scores showed the peas to be high in lysine and isoleucine and low in methionine and leucine. The protein efficiency ratio (PER) increased with steam-processing up to 11 minutes, after which the PER decreased. The vitamin C content was reduced due to heating time but was not affected by the heat process method. The niacin and riboflavin contents were reduced due to process method and process time. Thiamin content was not affected by processing. The beta-carotene content was not affected by process method. Beta-catotene content was reduced in first phases of heating, after which the content remained constant. The succulent peas had a higher beta-carotene content than did the dry peas. The contents of calcium, potassium, and sodium were affected by process method. Calcium was lost to a greater extent in the steam-processed peas. The potassium content was only reduced in the water-processed peas and the content was higher in the dry peas than in the succulent peas. The sodium content was not affected by process time, but the content was higher in the water-processed peas. The phytate content was little affected by processing. The trypsin inhibitor activity was affected by the process time, process method, and the maturity of the peas. The steamed peas lost the trypsin inhibitor faster than did the water-processed peas. The process method, process time, and maturity of the peas affected the firmness of the peas. The water-processed peas were softened more than were the steam-processed peas. The succulent peas were softer than the dry peas. The color of the peas was altered by processing. Processing had little affect on the L values. Processing decreased the "b" values and increased the "a" values. The succulent peas had a "-a" value and the dry peas had a "+a" value. With few exceptions, the steam-processed peas retained their nutrients better than the water-processed peas. One exception to this is the calcium content. The color of the steam-processed peas was altered less than the color of the water-processed peas. The PER reached an optimum at a time when the peas were still too firm to be comsumed.