How postharvest variables in the pulse value chain affect nutrient digestibility and bioaccessibility

Abstract

Pulses are increasingly being put forward as part of healthy diets because they are rich in protein, (slowly digestible) starch, dietary fiber, minerals, and vitamins. In pulses, nutrients are bioencapsulated by a cell wall, which mostly survives cooking followed by mechanical disintegration (e.g., mastication). In this review, we describe how different steps in the postharvest pulse value chain affect starch and protein digestion and the mineral bioaccessibility of pulses by influencing both their nutritional composition and structural integrity. Processing conditions that influence structural characteristics, and thus potentially the starch and protein digestive properties of (fresh and hard-to-cook [HTC]) pulses, have been reported in literature and are summarized in this review. The effect of thermal treatment on the pulse microstructure seems highly dependent on pulse type-specific cell wall properties and postharvest storage, which requires further investigation. In contrast to starch and protein digestion, the bioaccessibility of minerals is not dependent on the integrity of the pulse (cellular) tissue, but is affected by the presence of mineral antinutrients (chelators). Although pulses have a high overall mineral content, the presence of mineral antinutrients makes them rather poorly accessible for absorption. The negative effect of HTC on mineral bioaccessibility cannot be counteracted by thermal processing. This review also summarizes lessons learned on the use of pulses for the preparation of foods, from the traditional use of raw-milled pulse flours, to purified pulse ingredients (e.g., protein), to more innovative pulse ingredients in which cellular arrangement and bioencapsulation of macronutrients are (partially) preserved.

Utilizing Hydrothermal Processing to Align Structure and In Vitro Digestion Kinetics between Three Different Pulse Types

“…Hydrothermal processing times have been described to affect starch and protein digestion in pulses to different extents [ 4 ]. ICC isolated from BB and CP subjected to three distinct processing times achieving complete softening were used to study the effect of (hydrothermal) processing on starch and protein digestion.…”

“…Interestingly, (s)lower rates and levels of protein digestion of bean varieties (i.e., kidney bean [ 25 ], BB [ 60 ]) compared to other pulses, i.e., CP and PE, have been described in literature. Protein digestion in pulses has predominantly been linked to the effect of processing on protein structures [ 4 , 24 ] and little to be affected by processed-induced differences affecting enzymatic diffusion [ 24 , 31 ]. Processing has been described to render pulse protein either more susceptible or resistant for digestion, depending on the pulse type [ 4 ].…”

“…Protein digestion in pulses has predominantly been linked to the effect of processing on protein structures [ 4 , 24 ] and little to be affected by processed-induced differences affecting enzymatic diffusion [ 24 , 31 ]. Processing has been described to render pulse protein either more susceptible or resistant for digestion, depending on the pulse type [ 4 ]. Intrinsic differences at the level of molecular amino acid sequence [ 61 ].…”

“…Current literature suggests that protein and starch digestion kinetics both depend on pulse type and processing method and/or intensity [ 4 ]. Next to the ambiguity of current findings, systematic and comparative studies investigating the effect of processing intensity simultaneously on starch and protein digestion of different pulses are missing.…”

“…The degree to which macronutrients in pulses can be digested is highly dependent on both composition and structural features [ 2 , 3 ]. Various forms of processing affect the release of starch and protein from pulses and their subsequent digestion kinetics [ 4 ]. (Hydro)thermal treatment (cooking) renders pulses palatable and cotyledon cells can remain intact attenuating subsequently starch and protein digestion [ 5 , 6 ].…”