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Discoveries in Agriculture and Food Sciences - Vol. 12, No. 4

Publication Date: August 25, 2024

DOI:10.14738/dafs.124.16803.

Ulrich, S. F. B., Ngeh, A. N., & Ejoh, R. A. (2024). Effects of Foam Mat Drying on the Nutritional, Functional, Antioxidant, and Sensory

Properties of Soursop-Based Crisps. Discoveries in Agriculture and Food Sciences, 12(4). 58-77.

Services for Science and Education – United Kingdom

Effects of Foam Mat Drying on the Nutritional, Functional,

Antioxidant, and Sensory Properties of Soursop-Based Crisps

Saha Foudjo Brice Ulrich

Department of Biochemistry, Faculty of Sciences,

University of Bamenda, Bambili, Cameroon

Antoinette Nain Ngeh

Department of Food and Bioresource Technology,

College of Technology, University of Bamenda, Bambili, Cameroon

Richard Aba Ejoh

Department of Food and Bioresource Technology,

College of Technology, University of Bamenda, Bambili, Cameroon

ABSTRACT

This study investigates how foaming agents affect the nutritional, antioxidant,

physicochemical, and sensory qualities of soursop-based crisps, which are crucial

for meeting year-round market demand due to fruit cultivation limitations. Soursop

pulp was whipped with varying concentrations of soy proteins (SP6% and SP8%),

egg proteins (EP6% and EP8%), and whey proteins (WP6% and WP8%) to create

seven treatments, including a control without foaming agents. The samples were

then dried at 70°C, and their proximate and phytochemical composition, functional

properties, antioxidant activity, and sensory attributes were assessed. Compared to

the control, soursop-based crisps made with foaming agents contained higher fat

content (1.87–4.15%), with EP10% and WP8% showing high ash content (5.82–

6.60%), and WP10% and EP8% having elevated carbohydrate (85.92–87.66%) and

protein (2.75–3.88%) levels. EP10% had the highest swelling index (3.03%) and oil

absorption capacity (25.33%), while SP8% and SP10% exhibited greater water

absorption (61.33–63.67%). Traces of oxalates, phytates, and tannins were found

in all samples (<0.6 mg/ml). WP8% and WP10% had the highest flavonoid content

(10.16–10.71 mgQE/ml), while SP10%, EP10%, WP8%, and WP10% showed the

highest ferric-reducing activity (IC50:0.02–0.03 mg/ml). Most panelists (74% to

100%) favored soursop-based crisps from foam mat drying.In conclusion, foam mat

drying affected the nutritional, physicochemical, and sensory properties of

soursop-based crisps differently based on the type and concentration of foaming

agents used, suggesting the method's potential for long-term fruit preservation.

Keywords: Conventional drying, foam mat drying technology, soursop fruits, nutritional

potential, functional properties, and hedonic test.

INTRODUCTION

Fruits have been an integral part of the human diet for many years and are also considered food

supplements, internationally recommended as essential for healthy nutrition and well-being

due to their high quantity and quality of water, sugars, vitamins, minerals, and phytochemicals

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Ulrich, S. F. B., Ngeh, A. N., & Ejoh, R. A. (2024). Effects of Foam Mat Drying on the Nutritional, Functional, Antioxidant, and Sensory Properties of

Soursop-Based Crisps. Discoveries in Agriculture and Food Sciences, 12(4). 58-77.

URL: http://dx.doi.org/10.14738/dafs.124.16803

[1,2]. But a lack of knowledge regarding available fruits, their usage, and nutritional and health

implications poses challenges, particularly in addressing micronutrient deficiencies [3].

Nevertheless, a food-based approach, particularly dietary diversification, has the potential to

enhance the consumption of micronutrient-rich locally available foods such as fruits, which is

crucial in addressing hidden hunger [4]. However, the cultivation of fruits is often restricted to

specific seasons and regions, leading to the need for preservation techniques to meet year- round market demand [5].

Soursop (Annona muricate) is a highly sought-after exotic fruit due to its exceptionally pleasant

aromatic and juicy flesh. The milky soursop pulp, commonly consumed fresh, can also be

utilized in the production of candies, ice creams, beverages, and flavorings. Typically, the

quality assessment of soursop is based on visual aspects of the fruit, texture, flavor, and health

compounds present [6]. Additionally, parts of the soursop are consumed as a vegetable due to

their medicinal properties, which have been demonstrated to have antibacterial, antioxidant,

antidiabetic, antitumor, antifungal, antihypertensive, gastroprotective, and anesthetic

properties [7]. However, soursop is a highly perishable fruit with a short shelf life, and as a

result, there is a need for preservation methods. Processing of soursop into various products

not only reduces post-harvest losses but also helps retain the nutritional and phytochemical

quality of the processed products [8].

One of the techniques that can be utilized for preserving soursop (fruit) is drying to minimize

undesirable reactions while maintaining and enhancing the inherent quality of the starting fruit

[9], as drying is a preservation method that involves the removal of water vapor from the

surface of food material to its surrounding space, resulting in a dried material with an extended

shelf life [10]. However, throughout the drying process, alterations in the composition and

texture of food items may occur, such as nonenzymatic browning, reduction in bioactive

compounds, or diminished rehydration capacity of the dried food product [11]. Hence, it is

crucial to prioritize drying techniques that minimize nutrient loss, preserve texture, and

enhance the sensory attributes of the end product while keeping economic costs to a minimum.

Foam-mat drying is a method used for semi-liquid and liquid foods, especially those that are

heat-sensitive, viscous, and sticky, and cannot be dried using other techniques such as spray

drying [12, 13]. In this process, liquid food material is transformed into foam using surfactant

additives, such as foaming agents or foam stabilizers [14]. The foam is then spread out on a

sheet or mat and dried using hot air (40-90°C) at atmospheric pressure. Common additives

used in foam-mat drying include methyl cellulose, egg white, maltodextrin, and gum Arabic

[12]. The concentration of foaming agents and the drying conditions can affect the properties

of the foam-mat dried food products.

For example, a study on plum powder found that the concentration of the foaming agent and

the whipping duration had a substantial effect on the foam-forming characteristics, and the

foam mat drying process retained the antioxidant properties of the plum powder considerably

without causing any significant loss [15]. Another study on tomato powder found that the

antioxidant activity of the foam-mat dried powder increased with an increase in the foaming

agent concentration, while it decreased with an increase in the whipping time [16]. Little

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Discoveries in Agriculture and Food Sciences (DAFS) Vol 12, Issue 4, August- 2024

Services for Science and Education – United Kingdom

research has been conducted on the effect of various foaming agents (arabic gum, fish gelatin,

Portogel®, and albumin) on soursop drying and all these studies have focused on the

production of soursop powder [10,17,18]. Further research is needed to investigate the specific

effects of other foam mat drying on the processing of other soursop products. The objective of

this study was to investigate the effects of foam mat drying on the nutritional, functional,

antioxidant, and sensory properties of soursop-based crisps.

MATERIALS AND METHODS

Raw Materials and Chemical Acquisition

Ripe green soursop fruits (Annona muricate), weighing approximately 50 kg, were procured

from the local market (Main market, Bamenda, Cameroon) and transported to the laboratory

of the College of Technology, University of Bamenda. Subsequently, the soursop fruits were

manually sorted, washed with clean tap water, and stored at 4°C. All chemicals used in the study

are of analytical grade and were obtained from Sigma-Aldrich (United Kingdom).

Foaming Agents and Stabilizer

The method for preparing foaming agents, such as soy protein (SP), egg protein (EP), and whey

protein (WP), at different concentrations was implemented following the procedure outlined

by Salahi et al. [19]. The foaming agents were procured from Olam Group Limited (Lagos,

Nigeria) and prepared at the concentrations of 8% and 10% (w/v), while carboxymethyl

cellulose (CMC) was prepared at the concentrations of 3% and 4% (w/v). The preparation

process involved diluting each foaming agent in 100 ml of distilled water and allowing it to

stand for 30 minutes. Subsequently, the foaming agent was whipped using an electric hand

mixer at maximum speed for 5 min to form the foam, after which the stabilizer (CMC) was added

to stabilize the foam.

Experimental Design for Production of Soursop-Based Crisps

Completely Randomized Design (CRD) was employed as described in Table 1. The soursop

fruits, obtained from the local market (Main Market, Bamenda, Cameroon), were peeled and

unseeded. The unseeded fruit pulps were blended in a food processor (Braun Multi Quick 1

Hand Blender, 450 Watt, MQ 120, Poland) and packed in sterilized stainless-steel containers,

as described by Kandasamy et al. [20]. The soursop pulp was progressively added to the foam

and whipped for 10 minutes. After the whipping process, the samples were layered on a tray

approximately 1 cm thick and placed in an oven dryer at 70°C until the weight was constant.

Table 1: Mixture Design for the formulation of soursop-based crisps

Sample Soursop pulp Foaming agent Foam stabilizer

Soy protein (SP) Carboxymethyl cellulose

SP8% 200g 16g (8%) 6g

SP10% 200g 20g (10%) 8g

Egg protein (EP)

EP8% 200g 16g (8%) 6g

EP10% 200g 20g (10%) 8g

Whey protein (WP)

WP8% 200g 16g (8%) 6g