Small–scale Mechanical Carrot Washer for Research Sample Preparation

Carrot samples from field research studies of irrigation, fertility, and variety trials must be cleaned prior to weighing and grading. Soil and other foreign materials must be removed, especially for medium– and heavy–textured soils in which a preharvest irrigation is used to loosen the soil prior to hand harvesting. The objective of this project was to develop a low–cost mechanical carrot washer to reduce the labor and time requirements for sample preparation. Design considerations and operating constraints included sample sizes ranging from 3 to 11 kg (6.6 to 24.5 lb), a low operating speed to prevent bruising and breakage, low water pressures and flow rates, retention of small pieces, ease of sample loading and unloading, time and cost savings compared with manual washing systems, and operator safety. Carrot plant tops (stems and leaves) were removed prior to washing in this system. Food–grade washing capabilities were not a requirement of the washer. A nonimmersion, rotary washing system was developed using a horizontal 208–L (55–gal) barrel supported by roller drive wheels and equipped with a low–pressure spray wand. For carrot samples taken from a Heimdahl loam soil in east–central North Dakota, the water requirement per sample was approximately 11 to 15 L (3 to 4 gal), the optimum operating speed was 10 to 12 rpm, and the sample washing time varied from 5 to 7 min per sample. The article provides construction procedures, a bill of materials, cost estimates, photographs, engineering drawings, suggestions for improvements in the design, and safety considerations. Compared with manual washing of carrots, the mechanical washer achieved considerable improvements in sample processing speed and reduced labor requirements with no reduction in carrot quality. The washer should be adaptable for other types of root crops.