i THERMAL PROCESSING EFFECTS ON TOTAL ... - McGill University

Sehgal, (1992) reported that roasting may also improve the digestibility, colour, flavor,
shelf life and reduces the anti-nutrient factors of cereals and legumes. Commercial food
processing, by applying heat to seed products, helps to improve their protein quality by
destroying certain anti-nutritional compounds. Thermal treatment such as roasting of
flour by applying dry heat for 6-8 min at 104- 105°C has been shown to reduce its
enzyme activity and lower its trypsin inhibitor and haemagglutinin activities (Aguilera,
Lusas et al., 1982; Smith and Circle, 1972). Therefore, roasting being a simple and cost
effective processing method can be used in developing countries in order to achieve
maximum nutrient utilization from legumes like lentils. Under conventional heating
methods, thermal energy is transferred from the product surface towards its center 10-20
times more slowly than in a microwave-heated product. Roasting has both positive and
negative impacts on legume seeds and flours according to its duration.
2.3.2 Boiling (Hydrothermal processing):
Boiling is one of the commonest methods to cook any form of comestible
legumes. It can be done by two methods: (i) open pan boiling, or (ii) pressure boiling
In the traditional process, comestible legumes are cooked by open pan boiling,
where violent heating may result in loss of water soluble nutrients. Consequently, turning
down the heat once the water starts boiling, in order to slow down the cooking process, is
recommended. Appropriate cooking times for legumes can be affected by genetic factors,
physical structure, chemical composition and processing (Iyer et al., 1989).
Parihar et al., (1999) reported that proportionately more proteins were retained
under both forms of boiling, than fats or carbohydrates. Preliminary studies by Xu and
Chang, (2008) reported that the boiling process significantly reduced total phenolic
contents, free radical scavenging capacity in cool season comestible legumes. Porres,
López-Jurado et al., (2003) found that by pressure cooking lentils at 120°C for 30 min
reduces concentrations of trypsin inhibitor activity, phytate, and tannin content by 76%,
8%, and 12% respectively. In-vitro protein digestibility was improved by 81% after
pressure cooking compared to open pan boiling (Naveeda and Jamuna, 2006). Ur-
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