Abstract
Seaweed is an important global commodity since it is the source of many important products such as carrageenans, agar, alginates, and bioactive compounds. Seaweed processing is an energy intensive process since it involves heating large volumes of seaweeds in alkali solutions at high temperatures for up to six hours. To increase energy efficiency, an ohmic based processing system has been developed but has not been tested thoroughly. Therefore, the objective of this study was to identify optimum processing conditions for extraction of carrageenan from Eucheuma spinosum using ohmic heating technology. The experiment was conducted using Central Composite Design with four variables, i.e. extraction temperature, extraction duration, KOH concentration, and solution to seaweed ratio. Following the extraction process, carrageenan was recovered through precipitation using 90% isoprophyl alcohol solution. Results of experiments indicate that extraction yields varied from 29.6-62.4% dry basis with viscosity and gel strength varied from 259-290 mPa.s and 42.54-70.41 g/cm2 respectively. Statistical analysis indicated that extraction yield can be adequately modeled using the four variables and optimum extraction yield (61.59%), gel strength (53.48 g/cm2), and viscosity (284.51 mPa.s) were achieved at 95 °C extraction temperature, 240 minutes of extraction time, 0.4M KOH concentration, and 45:1 solution to seaweed ratio.
Highlights
Seaweed is an important global commodity since it is the source of many important commercial products such as carrageenans, agar, and alginates
Carrageenan gel strength and viscosity were significantly affected by extraction temperature, KOH concentration, and solution to seaweed ratio
Gel strength was a linear function of temperature and ratio and a quadratic function of KOH concentration while viscosity was a linear function of the three factors
Summary
Seaweed is an important global commodity since it is the source of many important commercial products such as carrageenans, agar, and alginates. Processing of seaweeds into valuable products is an energy intensive process. Current technologies in seaweed processing generally use double jacketed tanks supplied with steam for heating of processed seaweeds in alkali solutions. In those technologies, processing systems are complicated since they require dedicated steam generators and steam delivery systems. Simpler and more energy efficient processing technologies are needed and a recent publication by Hasizah et al (2018) has reported a novel technology for extraction of carrageenan using ohmic heating
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