Effect of heat and pectinase maceration on phenolic compounds and physicochemical quality of Strychnos cocculoides juice.

Ruth T Ngadze,Vincenzo Fogliano,Ruud Verkerk,Rosalia Ferracane,Anita R Linnemann,Loveness K Nyanga,Antonio D Troise,Edy De Brito

doi:10.1371/journal.pone.0202415

Abstract

Strychnos cocculoides fruit is an important food source for rural populations in Zimbabwe in times of scarcity. Its thick pulp tightly adheres to its seeds, causing pulp extraction constraints and waste during processing, leading to underutilisation. Therefore, pectinase maceration combined with heat treatments was studied to improve juice yield and juice quality. Metabolite profiling according to the heat map, FancyTile chromatic scale approach and phenolic compound content were used to compare the identified compounds. Prior to treatments, 16 known phenolic compounds, predominantly belonging to the phenolic acids, flavonoids and iridoid glucoside classes, were tentatively characterized for the first time in S. cocculoides using High Resolution Mass Spectrometry and LC/MS/MS. Overall, results showed that enzymatic treatments increased pulp yield (by 26%), physicochemical quality (38% increase in juice clarity), content of phenolic compounds (predominantly kaempferol, quercetin, caffeic acid, protocatechuic acid, iridoids) and antioxidant activity.The improved extraction of S. cocculoides pulp increases juice yield as well as juice quality by supplying larger amounts of phenolic compounds that have potential health benefits and act as dietary sources of antioxidants for the prevention of diseases caused by oxidative stress.

Highlights

Monkey orange species (e.g. Strychnos cocculoides) possess viscous flesh tightly adhering to hard seeds at 1:2 w/w ratio pulp and seed fresh weight (FW), hampering pulp extraction by simple pressing
Caffeic acid (CA), chlorogenic acid, protocatechuic acid (PCA), rutin, quercetin, myricetin, kaempferol, naringenin 7-O-glucoside, naringenin and catechin standards were purchased from SigmaAldrich (Italy), and loganic acid from Extrasynthese (France)
Maximum pulp yield and dry matter were obtained at 0.5% (w/v) pectinase and incubation for 300 min; a further increase in pectinase concentration had no significant effect on pulp yield

Summary

Introduction

Monkey orange species (e.g. Strychnos cocculoides) possess viscous flesh tightly adhering to hard seeds at 1:2 w/w ratio pulp and seed fresh weight (FW), hampering pulp extraction by simple pressing. The fruit is consumed fresh or after pulp extraction [1]. The limited seed– pulp separation reduces pulp yield with a subsequent increase in waste of nutritious food. Three extraction methods are used to increase the yield of pulp and juice viz., hot, cold or enzymatic pre-treatments [2]. Pre-treatment with pectinolytic enzymes has been used successfully for fruit pulp since the 1930s to soften tissues, ease seed/pulp separation and increase juice yield [3]. Enzymes hydrolyse glucoside bonds of the main chains of polygalacturonic acid

Methods

Results

Conclusion