Functional properties of syrup from malted and unmalted rice of different varieties: A comparative study

Abstract

The continued increase in Nigeria's rice production makes product diversification very fitting, even to underutilized indigenous/local varieties. Further, rice converted to malt can bring about useful products like syrup with enhanced characteristics. In this context, a comparative study involving some functional properties of syrup from malted and unmalted rice of different varieties was carried out. Syrup from either filtered or centrifuged starch hydrolysates of enzyme hydrolyzed rice (malted/unmalted) flours gave rise to filtered unmalted (FUHR), filtered malted (FMHR), centrifuged unmalted (CUHR), and centrifuged malted hydrolyzed rice (CMHR) groups. From these, functional properties, that is, pH, total soluble proteins (TSP), total dissolved solids (TDS), total solids (TS), dextrose equivalent (DE), titratable acidity (TA), apparent brix (°B), specific gravity (SG), syrup yield (SY), and some minerals [calcium (Ca), iron (Fe), magnesium (Mg), and zinc (Zn)] were determined. Results showed syrup from malted with significantly higher (P < 0.05) SY, Brix, pH, SG, TS, TDS, and TSP, but significantly lower (P < 0.05) TA, DE, and mineral contents (Ca, Zn, Fe, and Mg) over the unmalted group. Some significant interactions (P < 0.05) were found, between rice variety, treatment and separation method (TS, TDS, DE, Brix, SY, and Ca), rice variety and treatment (TSP, Zn, Mg, and Fe), as well as rice variety and separation method (TSP, pH). In addition, some positive and negative significant (P < 0.05) correlations between the studied functional properties were found. Overall, malting and processing methods can influence the functional properties of rice syrup-an acceptable specialty ingredient for brewing/beverage production. PRACTICAL APPLICATION: Through the application of exogenous enzymes, rice syrup has been successfully produced from locally bred/improved rice varieties commercially available in Nigeria. By comparing some functional properties of syrup from malted and/or unmalted rice, the current research provides useful evidence that locally available rice varieties are potential candidates for product diversification to the food/brewing, pharmaceuticals, and other industries, not only in Nigeria but also in the West Africa subregion.

Keywords: centrifugation; correlation; filtration; functional properties; malting; rice syrup.