Phenolic contents, antioxidant potential and associated colour in sweet sorghum syrups compared to other commercial syrup sweeteners

Background: Knowledge of the bioactive content of sweet sorghum syrups compared to other common food-grade syrups, will expand their utilisation as a food source. Total phenolic content (TPC), phenolics evaluated by high pressure liquid chromatography (HPLC), antioxidant 2,2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging activities, and oxygen radical absorbance capacity (ORAC) as well as colour of high fructose corn syrup (HFCS), corn, honey, maple, agave, rice and grain sorghum syrups were compared to ten commercial sweet sorghum syrups.

Results: Sweet sorghum syrups contained markedly higher (P ≤ 0.05) TPC (6471 ± 1823 mg/L) compared to the other syrups (596 ± 497 mg/L). HFCS, corn, white grain sorghum and rice syrups had negligible and low DPPH radical scavenging activities and ORAC values, respectively. DPPH activities, ORAC, and colour values of the sweet sorghum syrups were also markedly (P ≤ 0.05) higher than other syrups and highly related. The predominant phenolic components identified in sweet sorghum syrups were phenolic acids. Ellagic acid and protocatechuic acid were found in sorghum syrups ranging in concentration from 335-1177 μg/g and 53-485 μg/g, respectively. Sinapic acid was detected in several sorghum syrups, ranging in concentrations between 21-3654 μg/g.

Conclusion: HFCS, corn, white grain sorghum and rice syrups demonstrated low bioactivity with negligible and low DPPH activities and ORAC values, respectively. The TPC, DPPH, ORAC and colour values of the sweet sorghum syrups were related to each other and markedly (P ≤ 0.05) higher than for other syrups. Phenolic acids were the predominant phenolic compounds identified in sorghum syrups and represent potential for health benefits. This article is protected by copyright. All rights reserved.

Keywords: Sweet sorghum; antioxidant activity; bioactives; colour; commercial syrups; phenolics.