Bioactive Nutrient Retention during Thermal-Assisted Hydration of Lupins

Abstract

Lupin, an arid pulse, is gaining popularity as a super food due to its superior nutritional properties. However, it has not been considered for large scale thermal processing, e.g., canning. The present work evaluated the best time/temperature combination to hydrate lupins for canning with minimum losses of bioactive nutrients, pre-biotic fibre, and total solids during hydration. The two lupin species showed a sigmoidal hydration behaviour, which was adequately modelled by the Weibull distribution. The effective diffusivity, Deff, increased from 7.41 × 10−11 to 2.08 × 10−10 m2/s for L. albus and 1.75 × 10−10 to 1.02 × 10−9 m2/s for L. angustifolius with increasing temperature, namely, from 25 °C to 85 °C. The lag phase decreased from 145 min to 56 min in L. albus and 61 min to 28 min in L. angustifolius. However, based on the effective hydration rate, reaching the equilibrium moisture, minimum loss of the solids, and prebiotic fibre and phytochemicals, 200 min hydration at 65 °C can be regarded as the optimum temperature of hydration. The findings are thus relevant for designing the hydration protocol to achieve the maximum equilibrium moisture content and yield with the minimum loss of solids (phytochemicals and prebiotic fibres) for L. albus and L. angustifolius.

Leaching of Phytochemicals from Beans during Hydration, Kinetics, and Modeling

“…Perera and co-workers reported that hydration significantly increases the RFOs content in hydration water of two lupin varieties in the range of 20-80 times [11]. The study highlighted the dominant role of temperature in causing RFO to leach out during hydration.…”

“…During imbibition, the water travels into the internal structures of the grain, leading to swelling and softening of the cell walls and tissues [9,13]. Grains are porous media consisting of a complex network of microscopic cracks and crevices, which can take the form of intercellular spaces or dents on the starch, proteins, or cell wall polysaccharide networks [11,14]. These pores are the major water uptake pathways during the imbibition process.…”

“…The primary aim is to facilitate the softening of the beans and eliminate anti-nutritional factors such as saponins, lectins, and phytates [7][8][9]. However, with these antinutritional factors, several nutritious compounds like polyphenolics, proteins, and fibers also leach out into the hydration water, which eventually ends up into the waste streams [9][10][11]. While several pressing reasons necessitate studying phytochemical leaching during hydration, we can class them into two categories: scientific reasoning and industrial reasoning.…”