Abstract:
Turmeric spent, the residue remaining after oleoresin extraction from turmeric,
contains a significant proportion of starch. This study aimed to identify the best
protocol for starch isolation from turmeric spent (TS) and to optimize the parameters
to maximize its yield. Initially, starch was isolated using three methods: water
steeping [WS (12 h in 27℃ and centrifuged at 3000 rpm for 30 minutes)], acid
steeping [AS (1% ascorbic acid for 18 h in 27℃ and centrifuged at 5000 rpm for 30
minutes)], and alkaline steeping [KS (1% sodium hydroxide for 18 h in 27℃ and
centrifuged at 5000 rpm for 30 minutes)]. Subsequently, isolated starch was
characterized in terms of yield, purity, and functional properties. Results revealed that
AS yield at the highest significant (p<0.05) starch content [15.12±0.75% (w/w)]
compared to WS [14.33±0.47% (w/w)] and KS [10.07±0.34% (w/w)]. The highest
significant (p<0.05) purity of starch was also reported by AS [58.00±0.36% (w/w)]
compared to WS [56.47±1.12% (w/w)] and KS [55.13±0.40% (w/w)]. The functional
properties of starch obtained from AS: amylose content (52.11±8.58%) and solubility
(9.83±1.4%) were also significantly higher (p<0.05) than WS and KS. Whereas, the
gelatinization temperature, swelling power, viscosity, and water-binding capacity of
isolated starch from AS were reported as 67.7±1.58℃, 5.41±0.17 g g-1, 20.00±0.00
cP, and 51.13±1.40%, respectively. To further optimize starch isolation, AS was
employed under three acid concentrations (1%, 2%, and 3%) at two temperatures
(10℃ and 27℃), at three centrifugation speeds (3000 rpm, 4000 rpm, and 5000 rpm).
The findings indicated the highest (p<0.05) starch yield [17.52±0.37% (w/w)] for the
treatment combination of 2% ascorbic acid at 10℃ and centrifugation at 5000 rpm.
To conclude, the optimized AS method mentioned above is ideal for producing higher
starch yield and purity, demonstrating significant potential for use in the food and
pharmaceutical industries with further refining.
