Effects of selected environmental conditions on growth and carrageenan quality of laboratory-cultured Kappaphycus alvarezii (Rhodophyta) in Fiji, South Pacific

Abstract

The impacts of environmental conditions (temperature, salinity, and nutrients) on growth, semi-refined carrageenan yield, gel strengths, and viscosity were assessed on the red seaweed Kappaphycus alvarezii in laboratory culture. Results showed that K. alvarezii had a higher daily growth rate (0.94% day-1) at higher temperature (30 °C). Its semi-refined carrageenan yield was high (75.79%) at a combination of low salinity (25 ppt) and high temperature (30 °C). Conversely, gel strengths made out of semi-refined carrageenan from K. alvarezii cultured at low temperature (24 °C) demonstrated a higher compression (5.84 N) and high penetration strength (0.29 N). Highest viscosity (289.50 cP) was attained at a combination of high temperature, low salinity, and high nutrient concentration. Gels made from carrageenan of K. alvarezii grown in a higher temperature (30 °C) mixed with pineapple juice showed higher compression strength demonstrating that carrageenan extracted from cultured K. alvarezii is a good thickening agent for fruit jellies or similar food products that do not require refrigeration. This could benefit communities in rural, non-electrified communities/areas of Fiji and other South Pacific Islands that could use K. alvarezii as an alternative gelling agent in the making of food products contributing towards their food and economic security.