Evaluation of freeze-dried phenolic extract from cashew apple by-product: Physical properties, in vitro gastric digestion and chemometric analysis of the powders

Abstract

The aim of this study was to produce powders from the phenolic extract of the cashew by-product using maltodextrin and gum arabic as encapsulating agents to preserve these bioactive compounds and their antioxidative activity. Extraction was assisted by an ultrasound bath to increase the release of the bioactive compounds, resulting in the hydroalcoholic extract from cashew bagasse. The powders were physically and morphologically characterized, and their total phenolics, antioxidant activity and bioaccessibility were evaluated. All parameters were analyzed by chemometrics. In addition, UPLC-HRMS analysis was used to evaluate the phenolic profile of the extracts, revealing that the powders were able to protect some of the original compounds of the extract, such as catechin, the myricetin fraction and quercetin. The powders showed high total phenolic retention capacity, especially maltodextrin (2893.34 ± 20.18 mg GAE/100 g (DW)), which was the encapsulant that preserved the highest content of polyphenols and antioxidant activity after bioaccessibility in comparison to the unencapsulated extract. The powders showed low water activity (<0.2), low moisture (<8%), high solubility (>60 %) and low hygroscopicity (<4%). The SEM analysis showed that lyophilized extract samples resembled broken glass, which is characteristic of the lyophilization process, and in addition to a predominantly amorphous structure as demonstrated by the X-ray diffraction. The extraction and encapsulation of phenolic compounds from the cashew by-product through lyophilization and using maltodextrin and gum arabic as encapsulants enabled their preservation and potential use of these compounds by the nutraceutical or food industry, and can be used as food additive in order to enrich the content of compounds and the antioxidant activity of numerous products.

Keywords: Antioxidant; Bioaccessibility; Chemometrics; Encapsulation; Lyophilized powder; Phenolics; Ultrasound.

Graphical abstract

Fig. 1

UPLC-HRMS chromatograms in negative ionization mode of extract and powders derived from cashew apple phenolic extract. CAB: extract without encapsulants; MD: CAB extract + Maltodextrin; GA: CAB extract + gum arabic; MG: CAB extract + Mixture of Maltodextrin and gum arabic (1:1 w/w).

Fig. 2

Scanning electron microscopy for freeze-dried CAB extracts using different encapsulants with magnification of 300x (A) and 150x (B). MD: CAB extract + maltodextrin; GA: CAB extract + gum arabic; MG: CAB extract + maltodextrin and gum arabic (1:1 w/w).

Fig. 4

Physical properties of the encapsulated powder with different encapsulants. MD: maltodextrin; GA: gum arabic; MG: maltodextrin + gum arabic (1:1 w/w). Results expressed as mean ± standard deviation. The results followed by the same letter in the columns do not differ statistically with (p < 0.05).

Fig. 5

Classification results by PLS-DA modeling from the cashew apple by-product extract after encapsulation using different materials: gum arabic (GA in blue color), maltodextrin (MD in red), and a mixture of both materials using 50 % each (MG in green). The LV1 × LV2 scores coordinate system (a); LV1 × LV2 loadings from the physical and chemical parameters (b); influence plot by Hotelling T² × Q residuals (c); VIP plot with the most important variables for samples separation represented by scores higher than 1. TP: total phenolics; TP*: total phenolics after bioaccessibility; TAA: total antioxidant activity; TAA*: total antioxidant activity bioaccessibility; WA: water activity.

Fig. 6

A scatter plot (PC1 × PC2) and scores plot of CAB extract and their encapsulation. EX: CAB extract; MD: Extract CAB + Maltodextrin; GA: CAB extract + gum arabic; MG: CAB extract + Mixture of Maltodextrin and gum arabic (1: 1 w/w). Loadings in line from scores (b and c) for PC1 and PC2, respectively.

Flowchart 1

Process for obtaining the encapsulated CAB extract. CAB - Cashew Apple Bagasse.