Application of Edible Starch-Based Coating Including Glycerol Plus Oleum Nigella on Arils From Long-Stored Whole Pomegranate Fruits

Abstract

Two concentrations of cold‐pressed seed oil at a 300 and 600 ppm of Nigella sativa incorporated into starch‐based edible coating were applied onto pomegranate arils. Arils were individually treated with a solution of only starch coating (starch + glycerol, 2:1, v/v), 300 ppm oil + starch coating (starch + glycerol, 2:1, v/v and N. sativa oil, 300 ppm) and 600 ppm oil + starch coating (starch + glycerol, 2:1, v/v, N. sativa oil, 600 ppm). The untreated arils were used as the control group. All treatment groups were then stored at 4C for 12 days. The following parameters were examined on arils: softening, weight loss, total soluble solids (TSS) content, pH, titratable acidity (TA), L* value, chroma value, vitamin C content, anthocyanin content, browning index, microbial growth and organoleptic quality. Treatments with 300 and 600 ppm oil + starch coating greatly reduced softening of pomegranate arils, weight loss and % of browning index, loss of vitamin C, loss of anthocyanin content and delayed microbial decay. Results indicated that 300 ppm oil + starch coating significantly reduced weight loss, browning decay rates, the highest overall arils quality scores at the end of storage. Edible starch‐based coating including N. sativa oil appeared to be a good mixture for maintaining the quality of fruits during storage. PRACTICAL APPLICATION Several techniques have been used for preserving fruits by reducing their quality changes and quantity losses during storage, through a better understanding of the respiration process in fresh fruits. Edible coatings on fresh fruit can provide an alternative for modified atmosphere storage by reducing quality changes and quantity losses through modification and control of the internal atmosphere of the individual fruits. The present study demonstrated that Nigella sativa incorporated into starch‐based edible coating was applied onto pomegranate arils, which could preserve the quality. N. sativa oil can also be used as a preservative in the fresh‐cut processing industry.

Effects of edible coating on minimally processed pomegranate fruits

“…Pomegranate arils coated with chitosan and ascorbic acid showed no signs of deterioration, which rendered them acceptable for consumption. The findings obtained also showed that the a* value, which is related to the color stability and redness was significantly higher in the chitosan coated arils than in the control samples after 28 days of storage (Özdemir and Gökmen, 2017). It has been reported that the coating with chitosan and ascorbic acid significantly reduced bacteria, yeast and mold populations throughout the storage time (Ozdemir and Gökmen, 2017).…”

“…Oz and Ulukanli (2012) reported that there were statistically significant differences between the control and coating treatments throughout the storage. At the end of the storage, a 6% weight loss was measured in the control group, 3% in the starch coating itself, 2% in 300 ppm and 1% in 600 ppm oil + starch coating-treated arils (Oz and Ulukanli, 2011).…”

“…Oz and Ulukanli (2012) and Romeroa et al (2012) found that the highest softening aril ratio (%), which may mainly derive from the hydrolysis of starch to sugar and the degradation of pectin in the fruit cell wall associated with fruit ripening, was in the control arils. The coatings of A. vera gel (at 50 or 100%) alone or in a combination with acids (Romeroa et al, 2012) and the coatings of starch and N. sativa oil (Oz and Ulukanli, 2012) showed a significant delay of softening. Calcium chloride treatments (0.5% and 1%) maintained the highest firmness of arils, indicating significant differences between the treated and untreated arils (Shaarawi et al, 2016).…”

“…'Mollar de Elche', Punica granatum L. cv. 'Malas Saveh' and 'Mollar de Elche' pomegranates were harvested at the commercial harvest stage (Ergun and Ergun, 2009;Ghasemnezhad et al, 2013;Oz and Ulukanli, 2012;Varasteh et al, 2012;Romeroa et al, 2012;Öz et al, 2017). Pomegranates were washed with clear tap water or sterile water, and arils were subsequently removed manually.…”

“…Nabigol and Asghari (2013) dipped pomegranate arils in A. vera solutions, after which they were stored at 5 o C and 95% RH in permanent darkness for 3 weeks. Oz and Ulukanli (2012) prepared a coating solution by adding foodgrade starch powder (2%) and glycerol as a plasticizer (1%) to sterilized distilled water. The solution (a starch: plasticizer ratio of 2:1) was heated and boiled until completely dissolved.…”