Enhance the neutral taste and quality of chickpea protein by integrating acid extraction with conventional methods

Chickpea is one of the widely used pulse proteins for plant-based product development. However, chickpea protein has a beany flavor due to volatile compounds like alcohols, aldehydes, and ketones, produced by the enzyme lipoxygenase during the oxidation of unsaturated fatty acids. Additionally, conventional extraction causes insoluble aggregates and lipid oxidation which deteriorate overall quality.

The objective of the study was to (i) examine the effects of alkaline/acid extraction methods and their combinations on chickpea proteins, (ii) evaluate functionality and lipoxygenase activity, and (iii) analyze flavor compounds under varying extraction conditions.

Chickpea proteins were extracted using four methods: alkaline extraction (AK) (pH 9.0); acid extraction (AC) (pH 2.0); alkaline-acid extraction (AK+AC); and acid-alkaline extraction (AC+AK). The proteins were precipitated at their isoelectric point (pH 4.0), collected, and freeze-dried. Flavor compounds were identified using a Shimadzu Nexis GC-2030 with a GC-MS TQ8050NX detector. Functional properties were analyzed, such as solubility, emulsifying, and foaming capacity. Lipoxygenase and lipase activities were measured spectrophotometrically. Invitro protein digestibility and anti-nutritional factors were determined.

Lipoxygenase activity was significantly higher in AK (3.28 U/g), with reduced activity in AC (0.75 U/g), AC+AK (0.88 U/g), and AK+AC (1.16 U/g), indicating that acid-induced denaturation of the enzymes. The analysis of VOCs using GC-MS identified key compounds responsible for unpleasant aromas, including hexanal, trans-2-hexenal, heptanal, octanal, and 1-octanol, across all samples. Overall, AC reduced the total concentration of off-flavor compounds (0.026 mg/kg), while AC+AK had a higher concentration (1.322 mg/kg). Protein solubility was significantly higher in AK (p< 0.05) but reduced in AC, AK+AC, and AC+AK might be due to acid-induced structural changes, exposing hydrophobic regions and disrupting β-sheets and α-helices.

This approach offers a sustainable solution to overcome conventional extraction limitations while preserving critical functional and bioactive properties, supporting the development of high-quality pulse protein ingredients for sustainable food products.