Effect of drying methods on the retention of bioactive compounds in African eggplant

Abstract

African eggplants (Solanum aethiopicum L.) are a rich source of bioactive compounds and functional constituents that are beneficial to human health. However, the short shelf life of these vegetables can be a major cause of postharvest losses especially during peak harvesting season. Drying is one of the most convenient technologies for the production of shelf stable food products. However, drying can lead to considerable loss of the available bioactive compounds due to thermal degradation depending on the drying method and temperature conditions. This study investigated the effect of four drying methods (solar, oven, vacuum, and freeze) on the retention of total phenolics, beta‐carotene, antioxidant capacity, and lycopene in five African eggplant (S. aethiopicum) accessions (sangawili, manyire green, S00047A, AB2, and aubergine blanche). Samples were dried up to ~10% moisture content. The fresh and dried samples were analyzed for total phenolic content, antioxidant capacity, beta‐carotene content, and the lycopene content. In the fresh state, beta‐carotene, total phenolic content, and free radical scavenging activity ranged between 14.75 ± 0.50 and 29.50 ± 0.77 mg/100 g db, 751.21 ± 1.73 and 1,363.95 ± 2.56 mg/100 g GAE db, and 99.58 and 325.61 mg/ml db IC 50 value, respectively. The accession S00047 showed highest total phenolic content and lowest IC 50 value in the fresh samples. The results also showed that total phenolic content, antioxidant capacity, and beta‐carotene contents were significantly (p < .05) affected by drying method and drying temperature with freeze‐drying presenting the highest retention. Overall, 36.26%s–95.05% (total phenolics) and 31.44%–99.27% (beta‐carotene) were retained during freeze‐drying. Lycopene was only detected in the dried samples of the accession manyire green but absent in all the fresh samples of all the accessions. This study demonstrates that freeze‐drying was the most effective in retaining the highest bioactive compounds in African eggplants.

Phenolic distribution, antioxidant activity, and enzyme inhibitory properties of eggplant ( Solanum aethiopicum ) cultivated in two different locations within Nigeria

“…In addition, flavonoids are wellknown for their roles in preventing certain metabolic diseases (Wolfe & Liu, 2008). Phenolic contents of fruits are affected by number of factors, such as season, harvest time, drying methods, climatic, and environmental conditions (Banerjee & Bonde, 2011;Cordenunsi et al, 2002;Iqbal & Bhanger, 2006;Marcus & Grollman, 2002;Mbondo et al, 2018).…”

“…In addition, various biological activities of eggplant fruits have been reported, these include; anti-inflammatory and antitumor (Bhutani, Paul, Fayad, & Linder, 2010); hepatoprotective (Gupta et al, 2011); nephroprotective (Hussain et al, 2012); antidiabetic (Kar, Maharana, Pattnaik, & Dash, 2006). However, these biological activities could be related to inherent phytochemicals, such as phenolic compounds, flavonoids, and several steroidal alkaloids (Gürbüz, Uluişik, Frary, Frary, & Doğanlar, 2018;Mbondo, Owino, Ambuko, & Sila, 2018;Scalzo et al, 2010). These compounds have been reported to possess antioxidant properties and are beneficial to human health (Gürbüz et al, 2018;Khatoon, Sharma, & Dubey, 2018).…”

Red bell pepper (Capsicum annuum L.): Optimization of drying conditions and preparation of functional bread

“…To minimize the postharvest losses, the processing of bell peppers is a suitable way to preserve. In addition, various studies reported the retention of phenolics, antioxidants, and other phytochemicals during the processing of vegetables by drying (Kaur, Kaur, & Ahluwalia, 2019; Mbondo, Owino, Ambuko, & Sila, 2018). Sweet bell pepper powder and paste are added in a variety of foods as a flavoring, coloring agent and also used for enhancing the nutritional value of food products.…”

Assessment of the Processing Effects of Fresh Solanum Anguivi Berries on Biochemical Contents and Functional Properties of Powder

“…The total polyphenol content (TPC) was determined using the Folin-Ciocalteu method described by Mbondo et al (2018) with some modifications. The polyphenols were previously extracted by dissolving 2g of the powder in 20 mL of 70% hydromethanolic solution and vortexed for 3h.…”