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Fulltext Effect of drying temperature on Malaysia pomelo (Citrus grandis (L.) Osbeck) pomace residue under vacuum condition

Nur Farhana Abd Rahman, Amin Ismail, Nor Nadiah Abdul Karim Shah, Varith, Jaturapatr, Rosnah Shamsudin

Pertanika Journal of Science & Technology, 2019;27(101):57-66.
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Pomelo pomace (PP) from Malaysia Tambun White (PO52) variety, dried at different temperature under vacuum condition were evaluated. PP was obtained after extraction process and contained high moisture content (MC). Dried PP can be used as an alternative to livestock feed, hence, dried concentrated form was preferable. Nevertheless, drying process significantly affects the physico-chemical properties of a dried product. Therefore, the present study was carried out to discover the effects of drying temperature on the physico-chemical properties (MC, pH, vitamin C, browning index (BI) and total color change) of PP. The PP was dried at different drying temperature (50, 60, 70, 80 and 90°C) using a vacuum drying (VD) oven for 24 hr. The freeze drying (FD) process was used as a control. The result showed the MC gradually decreased with increasing drying temperature, of which similar trend was also observed for the water activity and total soluble solids (TSS). In contrast, pH showed increment in value with elevated drying temperature. Interestingly, at 90°C, vitamin C of VD (30.38 mg / 100 g DW) was higher than FD pomelo pomace (21.10 mg / 100 g DW). BI significantly increased as temperature increased. However, no significant changes were observed for total color change after VD. In conclusion, VD at 90°C showed the most recommended temperature because the composition of quality properties at this temperature was not significantly varied with control. These fundamentals information of pomelo pomace could be the guideline for postharvest technologist and food processing manufacturers for various applications.
Processing of coconut sap into sugar syrup using rotary evaporation, microwave, and open-heat evaporation techniques

Asghar MT, Yusof YA, Mokhtar MN, Yaacob ME, Ghazali HM, Varith J, et al.

J Sci Food Agric, 2020 Aug;100(10):4012-4019.
PMID: 32337729 DOI: 10.1002/jsfa.10446

BACKGROUND: Coconut sugar has a caramel color with a taste like brown sugar. It is commonly used as natural sweetener. However, coconut sugar has been produced from coconut sap using a traditional method that involves heating the sap at high temperature (>100 °C) in an open pan for a long period (3-5 h). This conventional method results in an over-cooked sugar, which leads to quality deterioration in terms of both its physical and chemical properties. The current study aimed to investigate the processing of coconut sap into sugar syrup using alternative processing techniques such as rotary vacuum evaporation (RE) and microwave evaporation (ME), comparing them with open-heat evaporation (OHE) technique.
RESULTS: Coconut sugar syrup produced by rotary evaporation at 60 °C and 250 mbar vacuum (RE-60) required the shortest production time (12.2 min) and the lowest processing temperature (54.8 °C) when compared with ME (13 min and 103.2 °C) and OHE (46.8 min and 101.6 °C). It also had a light brownish color with a higher L* value (35.17) than the ME (29.84) and OHE (23.84) methods. It was found to contain higher amounts of monosaccharides (fructose and glucose) and lower amounts of disaccharides (sucrose). Furthermore, the amount of energy required for RE-60 (0.35 kWh) was much less than for OHE (0.83 kWh).
CONCLUSION: This study provided an alternative processing method for the sugar processing industry to produce coconut sugar using the rotary evaporation method at 60 °C under 250 mbar vacuum with better physicochemical qualities, shorter processing time, and minimum input energy. © 2020 Society of Chemical Industry.

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