VEGETABLE AND FRUIT DEHYDRATION 179 



The care and skill exercised by trimmers have an important effect 

 on material losses. Proper training and supervision are especially im- 

 portant for trimming personnel. The plant operator should know at 

 what point a further increase in trimming rates results in excessive 

 raw-material losses. A saving of only 5 percent of the raw product 

 by slower and more careful trimming will pay for the employment of 

 two extra employees if the hourly labor cost per employee is $1, includ- 

 ing overhead, and the plant is handling 1 ton per hour of raw product 

 costing $40 per ton. If the plant processes 5 tons per hour, 10 addi- 

 tional trimmers could be justified by a 5-percent material saving. 



The efficient operation of each item of equipment is most essential. 

 The manner in which a machine is operated may cause variations in 

 processing costs greater than the capital charges on the machine. For 

 example, some cutters produce a considerable amount of chaff unless 

 fed at optimum rate. 



The problem of waste disposal is properly a part of preparation. 

 The quantity and kind of waste are largely the result of the prepara- 

 tion method. For instance, flame or radiant-heat peeling causes a less 

 serious sewage problem than abrasive peeling because the quantity of 

 waste is much smaller. Lye peeling results in a waste product that 

 may require special treatment, deepnding upon the disposition made 

 of it. 



Preparation costs include the following main items: Labor, equip- 

 ment charges, utilities (mainly water, power, and fuel for providing 

 steam), chemicals such as salt, lye, sulfur, etc., waste disposal (cost of 

 disposal or credit for sale of peels, trimmings, etc.) and other expenses, 

 including indirect and overhead costs. 



DRYING COST 



Drying covers the processing operation after delivery from the 

 blancher up to and including delivery from the finishing bins. If no 

 bins are used, drying ends with emptying of the trays or belts. Equip- 

 ment charges are a larger proportion of the drying cost than is the 

 case with preparation. For most vegetables, a few employees operate 

 a piece of drying equipment that may cost as much as all of the prepa- 

 ration equipment put together, or even more. For some fruits, the 

 ratio of drying cost to preparation equipment cost is even greater, 

 especially for those requiring no peeling or cutting. 



A minimum of labor costs can be achieved by the use of a continuous- 

 belt drier, or, with the tray drier, the installation of all practical labor- 

 saving methods and devices. 



The cost of heat and power for many products may not amount to 

 over 1 cent per dry pound. Direct-fired air heating is nearly always 

 more efficient than indirect heat where suitable fuel is available. The 

 installation of properly designed units is an engineering problem, but 

 the capital charges and operating costs of these units can be a subject 

 of cost analysis even before the unit is built or operated. Allowable 

 temperatures, maximum or minimum humidities, and desirable drying 

 times are predetermined technologically. Within the range of these 

 conditions, the plant operator must find the most economical point 

 of operation. 



Figure 76 shows the approximate coat of heat and power for evapo- 

 rating 100 pounds of water with different percentages of recirculation, 



