Altaf Hossain, Head of Applied Food and Nutrition Department for his valuable suggestions and inspiration. It is my honor to thank Mohammad Mozibul Haque, Assistant Professor, Department of Applied Food Science and Nutrition, for their moral support and cooperation during the investigation. I would like to thank all the teachers of the Faculty of Food Science and Technology for their valuable suggestions and support during the research program.
This study assessed the effect of different storage conditions on bioactive compounds (total anthocyanin content, total flavonoid content, total phenolic content) and antioxidant activity of pomelo and orange juice. Total anthocyanin content, total flavonoid content, total phenolic content, and antioxidant activity of pomelo and orange juice for 0 days, 7 days, 15 days, and 30 days were determined by calorimetric, aluminum chloride colorimetric, Folin-Ciocalteu, and DPPH assay methods, respectively, using UV-visible spectrophotometer. The results of total anthocyanin content, total flavonoid content, total phenolic content and antioxidant activity of pomelo juice at room temperature, refrigeration temperature and frozen temperature were varied from 1.34-0.45 mg/100 g mg QE / 100 g mg GAE / 100 g and µmol TE / 100 g for different days of stored pomelo juice respectively. The bioactive compounds and antioxidant activity for different days storage period of pomelo juice at room temperature, cooling and frozen temperature were significantly different (p<0.05).
Storage time and temperature have an impact on the bioactive compounds and antioxidant activity of pomelo and orange juice. Despite the reduction of these valuable components, the frozen temperature condition preserves better amounts of them than the storage temperature of others.
Introduction
2 | P a g e However, there are few papers worldwide, and none in Asia, regarding the preservation effect of these compounds. The effect of fruits on antioxidant activity, total phenols and anthocyanin compounds were evaluated by few researchers. Fruit juice is a popular way to consume fruit worldwide and changes during storage to phenolics and other bioactive compounds have been studied (Dawes & Keene, 1999; de Lima et al., 2014; Mendes Lopes et al., 2016). .
Furthermore, there is a need to increase our understanding of the effect of its storage on nutritional content. For these reasons, the effects of storage on bioactive compounds and antioxidant activity should be investigated.
Review of Literature
The orange is the most cultivated and popular citrus species worldwide (Liu et al., 2012). Citrus fruits are well accepted by consumers around the world due to their attractive colors, pleasant flavors and aroma, as well as their known nutritional and health-promoting values (Ballistreri et al., 2019). Flavonoids are the most abundant phenolic compounds found in citrus fruits (Tripoli et al., 2007). Flavonoids identified in citrus fruits include more than 60 species, according to the five classes mentioned (Horowitz and Gentili, 1977): flavones, flavanones, flavonols, flavans and anthocyanins (the latter only in blood oranges).
Moreover, these pigments are expressed in the young shoots and some flower tissues (new growth) of lemon, lime and citron, as well as in the peel (flavedo) of 'ISA Red Lemon' (Ballistreri et al., 2019). These compounds, and mostly anthocyanins, contribute to protect against certain cancers and cardiovascular diseases, reduce oxidative stress in diabetic patients and protect DNA from oxidative damage (Spormann et al., 2008). Citrus fruits and juices are rich sources of bioactive compounds, such as phenolic content, carotenoids, limonoids, coumarin-related compounds, folates, essential oils, pectins and vitamin C (Marti et al. 2009).
Phenolic compounds (PCs) are ubiquitously distributed phytochemicals found in most plant tissues, including fruits and vegetables (Laura et al., 2019). PCs possess numerous bioactive properties and, although they are not nutrients, dietary intake provides health protective effects, therefore post-harvest treatments have been used to enhance or preserve the content of PCs in fruits and vegetables (Ignat et al., 2011). There have been many attempts to find the antioxidant content, capacity and specific antioxidant compounds in citrus fruits (Al-Sayyed, et al., 2019).
Plant components, especially fruits, contain antioxidant components that can reduce oxidative stress (Agudo et al., 2007). The recommendation is to keep the refrigerator or display at 5°C or lower to ensure that food remains at 5°C or lower (James et al., 2008). Because many fruits are seasonal and have a limited shelf life, they require processing to maintain quality (Scibisz and Mitek, 2007). The nutritional qualities of juice, such as color, acidity, soluble solids, texture, total phenolics, antioxidant activity and anthocyanins can be affected during storage (Wicklund et al., 2005). The antioxidant activity, total phenolic content and fruit content of anthocyanins have been investigated by Wicklund et al. 2009). The total phenolics, antioxidant activity and anthocyanins of these fruits and their products may be affected during storage.
Materials and Methods
Samples of pomelo and orange juice were transferred to appropriate beakers to which absolute ethanol was added and left to shake on a shaker for 72 hours at room temperature. The TAC of pomelo extracts and orange juice was determined calorimetrically according to the method described by Unal et al. The color intensity of the extract was measured at a wavelength of 520 nm with a UV-VIS spectrophotometer (UV-2600, Shimadzu, Japan).
TFC of pomelo and orange juice extracts was determined using the colorimetric aluminum chloride method described by Chang et al., (2002). Aliquots of 0.5 mL of diluted extract or standard solution are mixed with 1.5 mL of 95%. TFC was calculated and expressed as milligrams of quercetin equivalents (QE) per grams of extract (mg QE/g).
The TPC of pomelo and orange juice extracts was determined according to the method described by Unal et al., (2014). The mixture was left for 3 minutes before 1.5 mL of sodium carbonate solution (75 g/L) was added and left for 60 minutes. TPC was calculated and expressed in milligrams of gallic acid equivalents (GAE) per gram of extracts (mg GAE/g).
The antioxidant capacity of the extracts was determined using DPPH assay as described by Azlim Almey et al., (2010). 11 | P a g e methanolic DPPH solution (2 ml) was added to 1 ml of each extract solution of different concentrations and the mixture was allowed to stand for 30 minutes and the absorbance was read at wavelength 517 nm. Antioxidant capacity based on the ability of DPPH free radicals to scavenge free radicals was calculated and expressed as milligrams of Trolox equivalents (TE) per grams of extracts (µmol TE/g).
Results
13 | P a g e 4.2 Total flavonoid content (TFC) in pomelo juice at different storage conditions Total flavonoid content (TFC) of pomelo juice at different storage conditions is shown in table 4.2. 14 | P a g e 4.3 Total phenolic content (TPC) in pomelo juice at different storage conditions Total phenolic content (TPC) of pomelo juice at different storage conditions is shown in table 4.3. Significant at P <0.05; Values with different superscript letters in a row indicate a significant difference; comparison performed across storage conditions.
16 | P a g e 4.5 Total anthocyanin content (TAC) of orange juice at different storage conditions Total Anthocyanin content (TAC) of orange juice at different storage conditions is presented in Table 4.5. 17 | P a g e 4.6 Total flavonoid content (TFC) of orange juice at different storage conditions Total flavonoid content (TFC) of orange juice at different storage conditions is presented in Table 4.6. 18 | Page 4.7 Total phenolic content (TPC) of orange juice at different storage conditions Total phenolic content (TPC) of orange juice at different storage conditions is presented in Table 4.7.
Significant at P <0.05; Values with different superscript letters in a row indicate a significant difference; comparison done on storage condition.
Discussions
The antioxidant capacity of different days of the storage period of pomelo juice in the room, at the temperature of refrigeration and freezing was significantly different (p<0.05). Significant losses in antioxidant capacity were observed as a result of storage, after 30 days at room, cold and frozen temperature. This is because the antioxidant capacity is usually sensitive to various factors such as storage time and temperature. 2012) observed the antioxidant capacity of blood orange (Citrus sinensis cv.
The changes in total anthocyanin content (TAC) for different days storage period of orange juice at room temperature, cooling and frozen temperature were significantly different (p<0.05). However, the total anthocyanin content (TAC) gradually decreased as the storage time increased. Significant losses in total anthocyanin content were observed as a result of storage after 30 days at room temperature, refrigeration and frozen temperature. The total flavonoid content in different days storage period of orange juice at room temperature, cooling and frozen temperature was significantly different (p<0.05).
22 | P a g e total flavonoid content was observed as a result of storage, after 30 days at room, refrigeration and frozen temperature. Total phenolic content of different days of storage period of orange juice at room, refrigeration and frozen temperature was significantly different (p<0.05). Significant losses in total flavonoid content were observed as a result of storage, after 30 days at room, refrigeration and frozen temperature.
This is because the total phenolic content is usually sensitive to several factors, such as storage time and temperature. 2016) prepared orange nectars reported a total phenolic content of 45.88 mg GAE/100 ml after 30 days of storage. The antioxidant capacity of orange juice on different days of storage at room, refrigerator and freezer temperatures was significantly different (p<0.05). This is because antioxidant capacity is usually sensitive to several factors, such as storage time and temperature. 2016) prepared orange nectars reported an antioxidant capacity of 4 µM TE/100 ml after 30 days of storage.
Conclusion
Recommendations & future perspectives
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Changes in bioactive compounds, antioxidant activity and nutritional quality of blood orange cultivars at different storage temperatures. Determination of storage duration and temperature effects on fruit quality parameters of blood orange (Citrus sinensis cv. Tarocco). Effects of hot water treatment on the storage stability of satsuma mandarin as postharvest spoilage control.
Effect of jam processing on phenolics and antioxidant capacity in anthocyanin-rich fruits: Cherry, plum and raspberry. Effect of jam processing and storage on total phenolics, antioxidant activity and anthocyanins of different fruits. Effect of hot water immersion on fruit quality, phenolic compounds and antioxidant capacity of Satsuma mandarin during storage.
Anthocyanin/polyphenolic fruit juice reduces oxidative cell damage in an intervention study with hemodialysis patients. Effect of storage time and temperature on the quality of fruit nectar: Determination of nutrient loss indicators. Concentrations of anthocyanins in common foods in the United States and estimation of normal consumption.
