DEVELOPMENT AND PERFORMANCE EVALUATION OF A MULTI-PURPOSE TUBER PEELING MACHINE

Abstract

Tuber processing has been mechanized in all areas of operation except for the area of peeling due to irregularity of tuber shapes, especially for cassava and yam tubers. This research is focused on the development and evaluation of a multipurpose tuber peeling machine with special consideration of tuber size and shape during peeling operation. The Multipurpose tuber peeling machine consists of wooden slats that form a cylindrical drum with concentrically arranged peeling tools, a hollow shaft, water retaining tank, a pipe, stainless net, waste water collecting trough, frame work and drive system. The machine peels and washes loaded tubers simultaneously. The power required to peel the tubers was 2.984 kW. The machine performance was evaluated using yam and cassava tubers. The tubers were grouped into sized and mixture of non-proportional tuber sizes (unsized). The sized tubers were further grouped based on the length (L), diameter (D), mass (M), into small (30 mm ≤ L ˂ 120 mm; 20 mm ≤ D ˂ 80 mm; 100 g ≤ M ˂ 900 g), medium (120 mm ≤ L ˂ 210 mm; 80 mm ≤ D ˂ 140 mm; 900 g ≤ M ˂ 1700 g) and large (210 mm ≤ L ≤ 300 mm; 140 mm ≤ D ≤ 200 mm; 1700 g ≤ M ≤ 2500 g) for yam tubers. In cassava tubers: small (20 mm ≤ L ˂ 110 mm; 10 mm ≤ D ˂ 70 mm; 50 g ≤ M ˂ 850 g), medium (110 mm ≤ L ˂ 200 mm; 70 mm ≤ D ˂ 130 mm; 850 g ≤ M ˂ 1650 g) and large (200 mm ≤ L ≤ 290 mm; 130 mm ≤ D ≤ 190 mm; 1650 g ≤ M ≤ 2450 g). The machine speeds used for the performance evaluation were 30 rpm, 40 rpm, 50 rpm, 60 rpm for yam tubers and 25 rpm, 40 rpm, 55 rpm 70 rpm for cassava tubers. The highest peeling efficiency recorded in the small category of yam tubers was 98.17 % at a machine speed of 30 rpm and that of medium and large tuber categories were 90.76 % and 93.09 %, respectively at machine speed of 40 rpm. In the small, medium and large categories of cassava tubers, the highest peeling efficiencies were at the machine speed of 40 rpm with the values of 61.69 %, 87.18 % and 91.9 %, respectively. The highest peeling efficiency recorded for unsized yam tubers was 94.19 % and unsized cassava tubers had the highest peeling efficiencies of 92.09 % at a machine speed of 40 rpm. The machine capacity for sized yam tubers was in the range 24 kg/h to 222 kg/h and sized cassava tubers was in the range 25.5 kg/h to 150 kg/h. The machine capacity for unsized yam tubers was in the range 56.57 kg/h to 96 kg/h and that of unsized cassava was in range 36.6 kg/h to 61 kg/h. The maximum flesh losses of 5.36 % and 2.2 % were recorded for sized yam and cassava tubers, respectively, while 13.21 % and 2.83 % were recorded for unsized yam and cassava tubers, respectively. These flesh losses were not recorded at the machine speeds of highest peeling efficiencies. At the machine speeds of 25 and 30 rpm, tuber size was inversely proportional to the peeling efficiency and for machine speeds of 40, 50, 55, 60 and 70 rpm, tuber size was directly proportional to peeling efficiency The machine had its highest peeling efficiency at the machine speed of 40 rpm for sized cassava, unsized cassava and yam tubers. The sized yam tuber diameters < 80 mm and ≥80 mm had highest peeling efficiencies at the machine speeds of 30 rpm and 40 rpm, respectiv