Postharvest shelf-life extension of fresh-cut guavas (Psidium guajava) using flaxseed protein-based composite coatings

Abstract

Flaxseed protein isolate from flaxseed meal was extracted by the alkali extraction method and its various functional, thermal and structural properties were investigated. Flaxseed protein isolate was standardised based on pH, solubility and purity. Protein solubility was found to be maximum at pH 11. Protein isolate shows maximum purity of 94.34% at pH 11. Oil holding capacity, water holding capacity and foaming capacity were estimated to be 3.86 ± 0.05 g/g, 2.85 g/g and 69%, respectively. Two crystalline peaks of 2Ɵ value were examined at 14 ° and 20 °. Thermogravimetric analysis (TGA) scan shows maximum weight loss of 16.12– 62% in the thermal range of 210–390 °C. Differential Scanning Calorimetry (DSC) curves revealed the denaturation temperature of protein isolate at 82.52 °C. Fourier Transformed Infrared Spectroscopy (FTIR) detected five different peaks at 1350.95 cm−1, 1383.35 cm−1, 1594 cm−1, 2816 cm−1, and 3423.77 cm−1. X-ray Diffraction (XRD) confirms the crystalline nature of flaxseed protein isolate. Flaxseed protein isolate based coatings were used to enhance the shelf life of cut guava fruit. The impact of flaxseed based composite coatings on colour, total soluble solids, titrable acidity, total phenolic content, total sugars, reducing sugars, ascorbic acid content, total plate count, firmness, drip loss, sensory scores and decay percentage of fresh-cut guavas at 4 °C temperature and 85% RH were determined. The results showed that coated samples were effective in maintaining the quality attributes of as compared to non-coated samples.