**1. Introduction**

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]. South Africa is leading the pomegranate production and export in the Southern Hemisphere, with an estimated production of 540,000 tonnes/1,200,000 cartons [5]. However, 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]. 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

pomegranate arils. However, drying is a preservation method that reduces the moisture contained in food, thereby extending the shelf-life of the product [9].

Dried pomegranate arils are often referred to as 'anardana' and are used in many traditional medicinal formulations to treat neurological and kidney disorders, as well as stomach and cardiac infections [10]. Due to its acidity profile, these dried arils help to improve digestion and mouth-feel [11]. Indian and Pakistani cuisines use 'anardana' as a condiment, but it can also be used as a substitute for tamarind and mango powder, or in culinary preparations of fruit salad, flavoured yoghurt and ice cream [12]. However, different drying methods, packaging and storage conditions are major factors affecting the inherent characteristics of the final product [13].

In addition to the decline in quality of pomegranate fruit during storage, different processing techniques could also have a negative impact on the quality of the finished product. Previous studies suggest that freeze-drying retains more bioactive compounds during the processing of fruit in comparison to other drying methods. For instance, Asami et al. [14] reported higher retention of phenolic concentration in 'Marion' blackberries during freeze-drying than hot-air drying. Shofian et al. [15] reported that the low temperature used to withdraw water from fruit material in freeze-drying helped to preserve the antioxidant capacity of tropical fruits. However, the freeze-drying process could be expensive and energy-consuming [16]. Among several drying methods available, hot-air drying is costand energy-efficient, making it one of the most commonly used methods for drying food materials [17]. However, it has a greater effect on the deformation of final products which is often characterised by dislocation of volatile substances and changes in physical properties [18].

'Wonderful' pomegranate is the most cultivated and consumed globally [19,20]. Currently, there has been a considerable rise in the export of pomegranate fruit grown in South Africa, with an estimated at approximately 70% of total production [21] compared to 56% export in 2013 [22]. 'Wonderful' is desirable because its bioactive compounds are better maintained during a prolonged storage duration compared to other cultivars. According to Arendse [23], the quality attributes of 'Wonderful' were maintained over five months in storage. Furthermore, the highest scavenging capacity exhibited by 'Wonderful' compared to the other eight pomegranate cultivars suggests the commercial potential of the cultivar [24].

The concentration of bioactive compounds in dried fruit products is influenced by numerous factors, including cultivar, harvest maturity, processing method and storage conditions [25]. While there are several studies on the effect of cultivar [26,27], there is a dearth of information on the impact of harvest maturity, extended storage of raw material and processing method [28] on the bioactive compounds of dried fruit, including dried pomegranate aril. In practice, fruit are kept in storage to allow processing at intervals based on demand or processing capacity. Fruit quality attributes degrade over time and will affect the quality of processed products, and hence, important to establish the maximum holding time of raw materials before processing. Therefore, this study aimed to examine the effects of hot-air and freeze-drying on the quality attributes of dried pomegranate arils during prolonged cold storage of whole fruit (raw material).

#### **2. Materials and Methods**

#### *2.1. Fruit Supply and Storage Condition*

Pomegranate fruit (cv. Wonderful) was handpicked at commercial harvest period from Blydeverwacht orchard in Wellington, (latitude 33◦01 00 S, longitude 18◦58 59 E) Western Cape Province, South Africa during the 2018/2019 growing season. Fruit were transported in an air-conditioned vehicle to the Postharvest Technology Research Laboratory at Stellenbosch University. Fruit without visible external discolouration or injuries were sorted to include fruit of uniform colour and size. After sorting, 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). Fruit were sampled at 0, 4, 8 and 12 weeks as described in the experimental flow chart (Figure 1).

**Figure 1.** Shows a description of the experimental flowchart.

Temperature (◦C) and relative humidity (% RH) within the cold rooms were taken every hour throughout storage. This was carried out with the use of a Tiny Tag TV-4500 data loggers (Gemini Data Logger, Sussex, UK) with a functional range of −40 ◦C to +85 ◦C and 0% to 100% RH.

#### *2.2. Characterisation of Fresh Arils*

Fresh pomegranate arils were periodically evaluated before processing for total soluble solids (TSS) by a refractometric method and titratable acidity (TA) by titrating to pH 8.1 with 0.1 N NaOH. Additionally, moisture content was measured using a digital moisture analyser. The Folin-Ciocalteu method was used to quantify the total phenolic content (TPC) and expressed as mean ± SE (milligram) gallic acid equivalent (GAE) per 100 mL of crude juice, while the pH differential method was used to determine the total anthocyanin content (TAC) [1,29], which was expressed as mean ± SE (milligrams) cyanidin-3-glucoside per 100 mL of crude juice. The antioxidant capacity (radical scavenging activity, RSA; ferric ion reducing antioxidant power, FRAP) was also measured in triplicate, according to Fawole and Opara [30] and expressed as Trolox equivalent (mM) per 100 mL of crude juice.
