Document Type

Technical Report

Publication Date



Water quality, food processing, vegetables, canning


The research was designed to test and/or develop new systems of washing, peeling and blanching, develop methods of utilization of solid wastes, and find ways to reduce wastestrength of effluent without affecting quality of vegetables for processing. The highest wastestrength of effluent from vegetable processing in the region was found in plants that were canning Irish potatoes, dry beans and hominy. The high volumes of water used for washing spinach and leafy greens and the physical damage to the washed product is one of the major problems. Repetitive washing of spinach in the same water did not affect quality as long as there was sufficient rinsing after the second wash. The levels of COD, TSS, TS, SS, PO4 and NO3 did not build up to prohibitive levels by the reuse of water as long as adequate make-up water was added. Steam blanching, which leaches out much less soluble constituents, can be substituted for water blanching by using appropriate times and temperature for different vegetables. The greater retention of nutrients in steam blanched vegetables was demonstrated in different vegetables grown and processed under different conditions. Data from research on the canning of dry beans indicated that the high wastestrength can be reduced by shortening the soaking time, controlling the temperature of soaking and processing without blanching without changing the quality appreciably. It appears that the present method of hominy preparation and processing can be altered to reduce pollution. By dipping corn in 10% lye solution, followed by heating and scrubbing, corn can be peeled and bleached efficiently. Most of the heavy solid waste can be isolated before the final rinse of the peeled corn. The prototype leafy greens washing system decreased the use of water by 70% on spinach, turnip greens and mustard. Water quality data showed that wastestrength of the effluent from washing was reduced over 50%, as compared to industrial washers, primarily due to less physical breakage. Less nutrients were leached out in greens washed by the experimental washer than the industrial washer. High alkalinity solid wastes from peeling Irish and sweet potatoes can be fermented and stored as long as 9 months without any great change in carbohydrates and total dry matter. There was an increase in sugar content and a decrease in starch content during fermentation. The quality of the sweet potato waste appeared to be excellent after storage when mold inhibitor was sprayed on vats. Irish potato waste storage created more odor problems unless the fermentation temperature was controlled at 25 to 30°C.

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