Comparative Effects of Silver Nanoparticles, Sucrose and Sodium Chloride as Osmotic Solutions for Tomato Slices: Antioxidant Activity, Microbial Quality and Modelling with Polynomial Regression Model

Luqmon Azeez,Ayoade L Adejumo,Agbaje Lateef,Abideen A Wahab,Kawthar Raji

doi:10.17159/0379-4350/2019/v72a4

Abstract

This study has reported comparative effects of silver nanoparticles (AgNPs), sucrose and sodium chloride as osmotic solutions on antioxidant activity and microbial quality of 10 mm tomato slices. 40 g of tomato slices were dehydrated osmotically (OD) at different temperatures (60,70 and 80 °C) and time (30,60,90,120150 and 180 min). Water loss, solid impregnation, water and solid diffusivities of tomato slices were found to increase with increase in solution temperatures and concentrations with AgNPs having the greatest influence. Antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl increased with increase in solution concentrations but decreased with increase in temperature. Three-way ANOVA (R2 = 0.998) revealed additive statistically significant effects of osmotic agents, concentrations and temperatures on antioxidant activity; F(854) = 67.854, P = 0.00. Polynomial regression analysis with response surface methodology validated experiments such that for each unit increase in concentration and temperature, antioxidant activity increased with good coefficients of determination; sucrose (R2 = 0.87), NaCl, (R2 = 0.89) and AgNPs (R2 = 0.91). Potato dextrose and nutrient agars were used for isolating and identifying microorganisms in OD tomato slices. Tomato slices dehydrated with AgNPs had the highest microbial inhibition of fungi with growth occurring after 7 days, unlike in treatments with sucrose and NaCl where fungal growth appeared after 2 and 5 days, respectively. Aspergillus niger was the most prevalent fungus. It can be concluded that AgNPs may serve as a viable means to dehydrate and preserve tomatoes without loss of antioxidant activity. Keywords: Osmotic dehydration, polynomial regression, response surface, antioxidant activity, three-way ANOVA, silver nanoparticles.

Highlights

Tomatoes (Lycopersicon esculentum) are essentially beneficial vegetables containing polyphenols, carotenoids, vitamins and minerals that can be either eaten raw or processed.[1,2,3,4,5] Studies have established that consumption of tomatoes with inverse correlation with risk of degenerative diseases
Isolation and Identification of Microorganisms Potato dextrose agar (PDA) and nutrient agar were the growth media prepared for microbial isolation
Solutions of tomato samples osmotically dehydrated with sucrose, sodium chloride and a comparative study with biogenic silver nanoparticles (AgNPs) were prepared by aseptically introducing 1 g of dried tomato samples into 10 mL of distilled water and was serially diluted to 10–3, 10–5 and 10–7

Summary

Introduction

Tomatoes (Lycopersicon esculentum) are essentially beneficial vegetables containing polyphenols, carotenoids, vitamins and minerals that can be either eaten raw or processed.[1,2,3,4,5] Studies have established that consumption of tomatoes with inverse correlation with risk of degenerative diseases This stems from the antioxidant, anti-inflammatory and anti-cancer properties of bioactive compounds contained in tomatoes.[4,6] Quality of tomatoes is affected by microbial degradation because of high moisture content which aids rottenness and allows potent mycotoxin producers such as Aspergillus, Trichoderma, Fusarium, Curvularia and Penicillium species to thrive, making rotten tomatoes hazardous for consumption.[7,8,9,10].

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Results

Conclusion