Micronisation and hot air roasting of cowpeas as pretreatments to control the development of hard-to-cook phenomenon.
BACKGROUND
Cowpeas stored under conditions of high temperature and high relative humidity (HTHH) develop the hard-to-cook (HTC) defect. Cowpeas with HTC defect require long cooking times, limiting their utilisation. Heat pretreatments are aimed at inactivating the enzymes responsible for HTC defect development. In this study, two heat pretreatments, micronisation and hot air roasting, were evaluated to assess their effectiveness in controlling the HTC defect development in cowpeas after storage under HTHH conditions.


RESULTS
Micronisation and hot air roasting as pretreatments reduced the cooking time of cowpeas after storage under HTHH conditions compared with the control. The differences in the effectiveness of HTC defect control between micronisation and roasting were dependent on the degree of phytase inactivation on day 0. Phytase activity was reduced by 45 and 70% by roasting and micronisation pretreatments respectively. Reduced phytase activity was associated with higher phytate and soluble pectin contents in micronised cowpeas than in roasted cowpeas after HTHH storage. This observation is in agreement with the phytase-phytate-pectin theory.


CONCLUSIONS
Micronisation was more effective than hot air roasting in controlling the development of HTC defect. This was due to a higher degree of phytase inactivation in micronisation when compared with roasting.
Department of Food Science, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.
Kimondo E
KE
Ndungu
Mohammad N
MN
Emmambux
Amanda
A
Minnaar
D010832:6-Phytase / Q000378:metabolism; D003296:Cooking; D004032:Diet; D004044:Dietary Proteins / Q000378:metabolism; D007887:Fabaceae / Q000201:enzymology; D005511:Food Handling / Q000379:methods*; D005519:Food Preservation / Q000379:methods*; D006358:Hot Temperature; D006801:Humans; D006813:Humidity; D010316:Particle Size; D010368:Pectins / Q000378:metabolism; D010833:Phytic Acid / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D012639:Seeds / Q000378:metabolism
D004044:Dietary Proteins; D010940:Plant Proteins; D010833:Phytic Acid; D010368:Pectins; D010832:6-Phytase