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

ehind microwave heating involves oscillatory migration of ions which produces heat in
the food under the influence of an electric field (Brijesh et al., 2011). According to Meda
et al., (2005), microwave heating exploits the dielectric behavior of the substance in such
a manner as to generate heat only up to a certain depth from the surface of the product.
There is an exponential decay of microwave energy as the waves penetrate into the
product from the surface, depending on the dielectric properties of the substance.
Kadlec et al., (2001) found that the sucrose and monosaccharide content of dried
germinated peas was constant, but decreased after MW treatment to 78% and 83% of
original levels, respectively. Stewart and Raghavan, (2003) showed that MW drying
preserved TIA and retained higher quantities of fatty acids, to produce better quality
soybeans [Glycine max (L.) Merr.]. Microwave heating at a power density of 3 W g -1
using a 1:1.5 samples to water ratio retained a maximum amount of vitamin content in
red lentils (Dev et al., 2010). Sharma and Gujaral, (2011) found a decrease in TPC and
antioxidant activity in barley (Hordeum vulgare L.) (after sand roasting and microwave
roasting). The greater loss in TPC may be due to a longer heating time in the microwave
oven.
By applying microwaves processing to pulses such as chickpeas (Cicer arietinum
L.) and common beans (Phaseolus vulgaris L.) (Marconi, et al., 2000) reported changes
in the cooking quality, physiochemical characteristics, along with nutritional
modifications in starch and non-starch polysaccharides. Scanning electron microscopy of
microwave-heated and traditionally processed legumes shows similar effects with respect
to in-vitro starch digestibility. Gonzalez and Perez, (2002) reported that microwave
irradiation and extrusion cooking caused several changes in rheological, functional and
morphological characteristics of lentil starches. Both treatments reduced the retro
gradation tendency of lentil starch for the processing industry, which would be an
interesting for the processing industry, since this is one of the reasons that have limited its
commercial use. The in-vitro protein digestibility of microwave and pressure-cooked
comestible legumes varies significantly, but averages about 75% and 80%, respectively
(Khatoon and Prakash, 2004).
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