Abstract
In order to estimate weight loss percent of fruit and vegetables, we experimented with spinach. The results are as follows.
1. Equilibrium relationships between moisture content of products and relative humidity of the surrounding air can be easily determined within a few days by measuring the equilibrium relative humidity of the air in the small chamber in which products are kept at a constant temperature.
2. The equilibrium moisture content curves for spinach were expressed in the following equations.
Adsorption: 1-rh=exp(-1.14×10-4•T•M1.169) 2-1
Desorption: 1-rh=exp(-8.70×10-5•T•M1.170) 2-2
rh=equilibrium relative humidity, expressed as a decimal
T=absolute temperature of air [°K]
Me=equilibrium moisture content (dry basis)
3. Weight loss percent of spinach after harvest can be obtained from Eq. (2-2) and the following equations.
v=(1-M+100/M1+100)×100
M-Me/M1-Me=exp[-(K•t)n]
K=8.254×108•exp(-7.383×103/T)
n=6.24×10-3•v+0.537
v=water loss percent of product at any time after harvest
M=moisture content (dry basis) at any time
Me=equilibrium moisture content (dry basis)
M1=initial moisture content (dry basis)
K=rate of drying constant [hr-1]
n=constant
t=time in hours
v=centigrade temperature of air [°C]
