Cinética de resfriamento e congelamento dos frutos de cajá (Spondias lutea L.)

Abstract

This present work had the objective to determine some chemical features (pH, soluble solid) and physicals (volume, dimensions, circularity, spfericity, specific mass and specific heat) of the cajá fruit in different temperatures, and to study the kinetics of freezing the caja fruits in the temperature of-30, -60 and -90°C. the curves of cooling were obtained in cooling cameras at 50 m.min"1 speed and the freezing curves in the Kryostat NI80 at the air freezing speed of 35 m.min"1. Based on the results, we can conclude that: a) the average circularity of caja is 69,53%, the average spfericity is 69,99% and the average dimensions of the bigger diameter and the smaller diameter are of 39,94 mm and 28,32 mm, respectively, the spoke that refers to the sphere with the same volume of the object is in average of 15,86 mm; and the average volume is of 16,10 cm"3 and its average consistence is 0,50 kg.cm"2; b) Refering to the chemical features studied from caja, its average pH is of 2,61 and its total soluble solids are of 14,72 °Brix. Talking about its thermophysicals properties and kinetics de cooling we can conclude that; c) The average specific mass for temperatures above the freezing mark (5,10 and 15°C) was of 0,89 g.cm"3 and the average specific heat of 0,8402 cal.g^.X"1; the diffusivity therrnal ranged from 1,39 x IO"7 m2.s"' and the therrnal condutivity from 0,406 to 0,435 W.irfVX"1 both in function of the decreased temperature form 15, 10 to 5°C; d) The necessary time for the caja fruit to be coolled in the temperatures of 15, 10 and 5°C until one rate temperature of 0,1 was de 22,40 and 60 minutes respectively. Talking to the conclusions referring to the thermophysicals and kinetics of freezing of the caja fruit, we can say that: e) The therrnal diffusivity during the freezing from 2,8. IO"7 m2.s_1 to 2,452.10"7 m2.s"!, in the Phase I of the cooling and from 3,1082. IO"7 m2.s"' to 3,2539.10"7 m^s"1 in the Phase III of the freezing (post freezing); f) the therrnal conductivity during the freezing ranged from 0,877 W.m\°C~\ in the Phase I of the freezing (cooling) and from 0,4608 W V . X " 1 to 0,3575 WV.OC"1 in the Phase III of the freezing (post-freezing); g) the caja fruit took 75 minutes to be freezing (Phase II) in a temperature of-30°C, 44 minutes in a temperature of-60°C and 40 minutes in a temperature of-90°C.