Thawing and tempering 169 Temperature of thawing medium 40℃c30°c20℃10° bE365885 6 kg leg.-30°to0°c of-10C under the fastest and slowest thawing conditions) Thawing time(h) A= Vacuum steam heat b= Water, 0.023ms C= Water 0. 006ms Fig 8.2 Prediction of thawing times of frozen pork legs from-30-0C(source Bailey and James, 1974a) Table 8.3 Mean percentage weight losses(fresh to thawed states)for pork legs thawed in air. water or vacuum Thawing Velocity of Thawing temperature (C) medium(ms) 10 20 25 0.9(18) +1.0(27)+11(20 0.9(18) 1.0(14) 1.0(15) +1.0(8) +1.1(10) +12(8) 0023 +12(8) +11(13) +0.7(6) VHT +13(14) 0.2(14) 0.6(13) O Number of samples. Source: Bailey and James, 1974a. increasing the water velocity had very little additional effect. VHT was not appreciably faster than water thawing at any temperature, demonstrating that for materials of this thickness conductivity is the rate controlling factor The pork legs increased in weight by 1 +0. 3% under any of the condi- tions of thawing in air or water, with the exception of high velocity air where losses of 1% were recorded (Table 8.3). A similar increase was recorded in VHT at 10C but there were small losses of weight at 20 and 30C.increasing the water velocity had very little additional effect. VHT was not appreciably faster than water thawing at any temperature, demonstrating that for materials of this thickness conductivity is the rate controlling factor. The pork legs increased in weight by 1 ±0. 3% under any of the condi￾tions of thawing in air or water, with the exception of high velocity air where losses of l% were recorded (Table 8.3). A similar increase was recorded in VHT at 10 °C but there were small losses of weight at 20 and 30 °C. Thawing and tempering 169 5000 4000 3000 2000 1000 500 400 300 200 100 40 30 20 10 50 A B C D E 0 10 20 30 40 50 Thawing time (h) A = Vacuum steam heat B = Water, 0.023ms –1 C = Water, 0.006ms –1 D = Air, 5ms –1 E = Air, 0.25ms–1 3 kg leg. –30 ° to 0 °C 6 kg leg. –30 ° to 0 °C Thawing from –10 ° to 0 °C (Shaded area shows reduction in thawing time for initial temperature of –10 °C under the fastest and slowest thawing conditions) 40 °C 30 °C 20 °C10 °C 5 °C Temperature of thawing medium Surface film heat transfer coefficient (W m–2 °C–1) Fig. 8.2 Prediction of thawing times of frozen pork legs from -30–0 °C (source: Bailey and James, 1974a). Table 8.3 Mean percentage weight losses (fresh to thawed states) for pork legs thawed in air, water or vacuum Thawing Velocity of Thawing temperature (°C) medium medium (m s-1 ) 10 20 30 Air 0.25 +0.9 (18) +1.0 (27) +1.1 (20) 5.5 +0.9 (18) -1.0 (14) -1.0 (15) Water 0.006 +1.0 (8) +1.1 (10) +1.2 (8) 0.023 +1.2 (8) +1.1 (13) +0.7 (6) VHT +1.3 (14) -0.2 (14) -0.6 (13) () Number of samples. Source: Bailey and James, 1974a