Effects of maltodextrin on physicochemical properties of freeze-dried avocado powder

T Chuacharoen,J Moolwong,T Chyrsirichote

doi:10.26656/fr.2017.5(6).739

Abstract

The effect of maltodextrin on the moisture sorption isotherm, glass transition temperature (Tg), and degree of caking of freeze-dried avocado samples at room temperature (25°C) was investigated. The incorporation of maltodextrin reduced the water sorption capacity of the powder due to its less hygroscopic nature. Parameters derived from the Guggenheim, Anderson, and de Boer (GAB) model describing the properties of absorbed water are discussed. The water absorption isotherm possessed the characteristic sigmoid-shaped type II isotherm curves and the model gave the best fit over the whole range of aw tested. The differential scanning calorimetric method was used to measure the Tg of freeze-dried avocado samples. Increasing the water content decreased the Tg, and Tg was increased with increasing maltodextrin content. Increased maltodextrin content to solid material in the freeze-dried sample was associated with less sensitivity to caking as evidenced by Tg values. In addition, increased maltodextrin content in the powders caused brighter, less yellowish, and more greenish coloration and protected color change including browning index. The antioxidant capacity was significantly decreased with increasing maltodextrin content. Thus, the effect of maltodextrin concentration on physicochemical properties was a promising way to preserve the physical property and chemical compounds in freezedried avocado powder.

Highlights

The consumption of fruits and vegetables containing high amounts of fiber and phytochemical agents plays an essential role in the maintenance of healthy eating
The total phenolic content and antioxidant activity were tested to evaluate the antioxidant capacity of phytochemical compounds remaining in the freeze-dried avocado powder
The Folin-Ciocalteu method works on the mechanism of oxidation-reduction reaction, whereas DPPH assay uses an electron transfer mechanism to stabilize radicals

Summary

Introduction

The consumption of fruits and vegetables containing high amounts of fiber and phytochemical agents plays an essential role in the maintenance of healthy eating. It contains high amounts of fats that are saturated and unsaturated fatty acids, carbohydrates, proteins, dietary fibers, vitamins, minerals, and phenol derivatives such as carotenoids (Alkhalaf et al, 2019). Considering its high nutritional value from the richness in phytochemical composition, the avocado possesses numerous health benefiting properties, such as antioxidant, anti-inflammatory, anticancer, and antimicrobial activities (Krumreich et al, 2018). The fresh avocado pulp has high levels of fat and moisture content, which caused the avocado to be a highly perishable fruit. To prolong the shelf life of avocado powder, the freeze-drying method is a suitable preservation method that prevents the loss of phytochemical compounds by a non-thermal process. Freeze-dried powders are typically produced in an amorphous state, and these solids theoretically undergo changes to crystallize in rheology at the glass transition temperature (Tg), which is defined as the temperature at which glass transitions change to the rubber state (Chiou and Langrish, 2007)

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