Abstract
This study investigated the effect of hot-air and freeze-drying on the physicochemical, phytochemical and antioxidant capacity of dried pomegranate arils during long-term cold storage (7 ± 0.3 °C, with 92 ± 3% relative humidity) of whole fruit over a single experiment. Extracted arils were processed at monthly intervals during 12 weeks of cold storage of whole fruit. After the 12-week storage period, hot-air and freeze-dried arils showed the least (3.02) and highest (23.6) total colour difference (TCD), respectively. Hot-air dried arils also contained 46% more total soluble solids (TSS) than freeze-dried arils. During the storage of pomegranate fruit, total phenolic content (TPC) steadily increased from 20.9 to 23.9 mg GAE/100 mL and total anthocyanin content (TAC) increased from 6.91 to 8.77 mg C3gE /100 mL. Similarly, an increase in TPC and TAC were observed for hot-air (9.3%; 13%) and freeze-dried arils (5%; 5%), respectively. However, the radical scavenging activity (RSA) reduced by 8.5 and 17.4% for hot-air and freeze-dried arils, respectively, after 12 weeks of cold storage. Overall, the parameters such as colour, TPC and TAC as well as the lower degradation in RSA stability during storage showed distinct differences in quality when using the freeze-drying method, which is, therefore, recommended.
Highlights
Pomegranate fruit (Punica granatum L.) is renowned for its bioactive phenolic content, including flavonoids, phenolic acids, tannins, ellagitannins, catechin, rutin and epicatechin [1,2]
11% of the total production is processed locally, and 9% is considered as waste due to disorders such as cracks, sunburn, scalds and bruises, which could affect the internal quality of the fruit [5,6]
Fresh fruit were packed inside standard open top cartons with the following dimensions: width 0.3 m, length 0.4 m, height 0.133 m and a total of 22 perforations and stored at 7 ± 0.3 ◦ C, with 92 ± 3% relative humidity (RH)
Summary
Pomegranate fruit (Punica granatum L.) is renowned for its bioactive phenolic content, including flavonoids, phenolic acids, tannins, ellagitannins, catechin, rutin and epicatechin [1,2]. These antioxidants have been implicated in the protection against heart, cancer, immune system and other chronic diseases [3,4]. Fruit similar to pomegranate usually has a small harvest window, whereas processing is carried out over a long period, and this requires the storage of raw materials for the production of niche products. Fifty per cent of fruit that do not meet export requirements are often converted into products such as jellies and juices, which have a short shelf life [7]. Caleb et al [8] reported a maximum flavour-life of seven days for Agriculture 2020, 10, 493; doi:10.3390/agriculture10110493 www.mdpi.com/journal/agriculture
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