Abstract
Pomegranate seed oil (PSO) is valued for its health-promoting compounds, yet maintaining its stability during storage and handling remains challenging for processors. Sustainable techniques to enhance the shelf-life of PSO are crucial for preserving its beneficial properties and expanding its use in food applications. Microencapsulation has the potential to preserve the quality of seed oils such as PSO, making them more suitable for food systems.
Emerging evidence suggests that microencapsulated seed oils can be used to formulate emulsions that help preserve the quality of minimally processed fruits and vegetables, including pomegranate arils. Applying this technology in pomegranate processing could reduce postharvest losses and support a circular food economy. This study aims to microencapsulate PSO for postharvest preservation of pomegranate arils, addressing the need for effective preservation strategies in the industry.
The first goal of this study was to evaluate different combinations of gum Arabic (GA) and maltodextrin (MD) (ratio: 1:0, 0:1, 1:1, 3:1, and 1:3) and establish the best formulation to develop PSO powders that can effectively preserve the physicochemical, techno-functional, and antioxidant properties of pomegranate seed oil. The scanning electron microscopy (SEM) studies revealed that the powders were porous and had flake-like shapes and textures, which were either smooth or wrinkled. The Fourier transform infrared (FT-IR) spectra showed peaks ranging from 2973.70 to 408.84 cm−1 and suggesting the presence of aliphatic, amine, aromatic, carboxylic acid, and hydroxyl groups. Overall, GA:MD ratios of 1:0 and 1:1 enhanced the colour, techno-functional attributes and preserved essential fatty acids such as stearic, cis-oleic, α-linolenic, arachidic, γ-linolenic, linoleic, and punicic acids. Contrary, GA:MD (3:1) produced powders with better ferric-reducing antioxidant power (FRAP) and 2,2-diphenyl-1picrylhydrazyl (DPPH) radical scavenging activities (RSA). These results indicated that no single formulation could produce a powder with all the desired qualities; however, formulations using GA alone or GA:MD ratios of 1:1 and 3:1 presented a huge potential to preserve the bioactive content and antioxidant capacity of PSO. These
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quality attributes are vitally important for the use of microencapsulated PSO in formulating emulsions for use as edible coatings of minimally processed foods.
The subsequent experiment investigated the effect of applying pomegranate seed oil emulsions prepared using GA:MD (1:1) as wall materials and functionalised with pomegranate peel extracts (PPE; 1, 3, and 5%) on the preservation of pomegranate arils during storage. Firstly, the developed emulsions were evaluated with respect to physical properties, such as stability, viscosity, microstructures, colour, and chemical properties, such as antioxidant and antimicrobial activity, before applied to pomegranate arils. Increasing the concentration of PPE in the emulsions improved their antioxidant activity and inhibition of E. coli (ATCC 35218) and L. monocytogenes (ATCC 23074) due to the increased presence of antioxidant compounds. With respect to the storage of pomegranate arils coated with emulsions, the duration of storage (p<0.05) had a significant impact on the quality attributes of pomegranate arils, such as texture, pH, and objective colour lightness. Meanwhile, storage and treatment (15% PSO and PPE concentration) had a combined influence (p<0.001) on attributes including total soluble solids, respiration rate, total acidity, redness, and total colour difference, making it difficult to conclude the effect of 15% PSOP and PPE concentrations on the studied quality attributes of pomegranate arils.
Overall, this research demonstrated that GA and MD can be used as binary blends to preserve PSO quality attributes and functional properties, especially formulations that use GA alone or in 1:1 and 3:1 proportion with MD. However, this is the first study to explore the impact of incorporating PSO and PPE in emulsions and applying them as an edible coating to preserve pomegranate arils. Finally, this study contributes to a circular food economy within the pomegranate processing industry and aligns with the United Nations Sustainable Development Goals by advancing practices that emphasize environmental sustainability and public health.