D. Fahloul et al., THE FRACTURE-TOUGHNESS OF PEA TESTA IN RELATION TO TEMPERATURE ABUSE DURING FROZEN STORAGE, Food research international, 29(8), 1996, pp. 791-797
Obtaining information on the textural quality of food materials in SI
units is desirable for objective quality control. Adapting standard ma
terials testing methods to biological specimens has the potential of p
roviding such objective measurements. Based on the approach of linear
elastic fracture mechanics, a tear test was used to measure the fractu
re toughness of the testa of frozen peas. The mean fracture toughness
obtained for an extension rate of 0.13 mm s(-1) was 212 J m(-2). The e
ffect of extension rate was investigated and showed that fracture toug
hness increased with increasing extension rate. Measurement of fractur
e toughness was applied to identify the effect of ''temperature abuse'
' in the pea testa. Following three thaw-freeze cycles, the specimen b
ecame more fragile and fracture toughness of pea testa decreased by ab
out 18%. Brightfield microscopy and low temperature scanning electron
microscopy were used to observe tissue changes resulting from temperat
ure abuse. Cell rupture in the osteosclereids and parenchyma layers wa
s associated with temperature-abused tissue. Slow freezing during the
thaw-freeze cycles caused formation of large ice crystals which disrup
ted the pea testa tissue. (C) 1997 Published by Elsevier Science Ltd o
n behalf of the Canadian Institute of Food Science and Technology.