Impact of Terahertz Frequency Irradiation on the Physicochemical, Nutritional, Microbial and Sensory Quality of Orange-Fleshed Sweet Potato–Soy Beverage

Abstract

The manuscript explored the effect of terahertz frequency irradiation on the physicochemical, nutritional, microbial load and sensory qualities of OFSP–soy beverages. The orange-fleshed sweet potato was processed into a beverage, and soy milk was added at varied ratios formulated: OFSP: soy milk: 90:10, 80:20 and 70:30 and pasteurised with electromagnetic irradiation at varied times (5, 10 and 15 min). The pH increase was 6.15, 6.21 and 6.24 at 5-min irradiation and 6.07, 6.11 and 6.18 at 15-min irradiation with 10%, 20% and 30% addition of soy milk. The Brix content was 9.30, 10.07, 12.01, 7.43, 8.06 and 9.91 at 5- and 15-min irradiation and 10%, 20% and 30% of soy milk addition. However, the microbial load was not detected when samples were irradiated for 10 and 15 min but was noticed at 5-min irradiation. Likewise, sensory qualities such as colour, taste, aroma, mouthfeel, aftertaste and overall acceptance of the beverage were improved with an increased range colour (5.90 to 6.98), aroma (6.30 to 6.98), taste (5.38 to 7.28), mouthfeel (5.29 to 7.18), aftertaste (5.26 to 7.30) and overall acceptance (5.78– to 7.54). 10-min electromagnetic irradiation pasteurisation with 90%:10% OFSP and soymilk had optimum beta-carotene with zero coliform counts and hence it is recommended. The outcome of this study could help to exploit the benefits of terahertz frequency irradiation machines in reducing microbial growth in the beverage industry.