Effects of drying on total polyphenols content and antioxidant properties of Carica papaya leaves.

BACKGROUND: Papaya is widely grown in Malaysia and normally only the fruits are consumed. Other parts of the plant such as leaves, roots, bark, peel, seeds and pulp are also known to have medicinal properties and have been used to treat various diseases. Papaya leaves also contain flavonoids, alkaloids phenolic compounds and cynogenetic compounds, and are also reported to be able to treat dengue fever. RESULTS: Studies were carried out on drying of papaya leaves using hot air (60, 70 and 80 °C), shade and freeze drying. Effective diffusivities were estimated ranging from 2.09 × 10-12 to 2.18 × 10-12 m2 s-1 from hot air drying, which are within the order of magnitudes reported for most agricultural and food products. The activation energy to initiate drying showed a relatively low value (2.11 kJ mol-1 ) as a result of the thin leave layer that eased moisture diffusion. In terms of total polyphenols content and antioxidant activities, freeze-dried sample showed a significantly higher (P < 0.05) total polyphenols content [2158 mg gallic acid equivalent 100 g dry weight-1 ] and antioxidant activities [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) = 571 mg TE 100 g DW-1 and 2,2'-diphenyl-1-picrylhydrazyl (DPPH) = 215 µg mg-1 ] compared to hot air and shade dried samples. CONCLUSION: Freeze dried sample retained the most total polyphenols content and showed the highest antioxidant activities in both ABTS and DPPH antioxidant assays. Hot air and shade drying are not conducive with repect to preserving the antioxidants as a result of possible thermal degradation at elevated temperatures and oxidations under prolonged drying condition. © 2020 Society of Chemical Industry.

Improving Malaysian cocoa quality through the use of dehumidified air under mild drying conditions.

BACKGROUND: Various studies have been conducted in the past to improve the quality of Malaysian cocoa beans. However, the processing methods still remain crude and lack technological advancement. In terms of drying, no previous study has attempted to apply advanced drying technology to improve bean quality. This paper presents the first attempt to improve the quality of cocoa beans through heat pump drying using constant air (28.6 and 40.4 °C) and stepwise (step-up 30.7-43.6-56.9 °C and step-down 54.9-43.9 °C) drying profiles. Comparison was made against hot air drying at 55.9 °C. RESULTS: Product quality assessment showed significant improvement in the quality of Malaysian cocoa beans. Quality was found to be better in terms of lower acidity (higher pH) and higher degree of browning (cut test) for cocoa beans dried using the step-up profile. All heat pump-dried samples showed flavour quality comparable to that of Ghanaian and better than that of Malaysian and Indonesian commercial samples. Step-up-dried samples showed the best flavour profile with high level of cocoa flavour, low in sourness and not excessive in bitterness and astringency. CONCLUSION: Dried cocoa samples from the step-up drying profile showed the best overall quality as compared with commercial samples from Malaysia, Indonesia and Ghana. The improvement of Malaysian cocoa bean quality is thus achievable through heat pump drying.