Influence of Ultrasound Parameters on Some Qualities of Frozen African Spinach

Abstract

Consumption of fresh and healthy vegetables in our diets aids protection from chronic diseases in humans. This study determined the effects of ultrasound as a pre-treatment technique on vitamin C, beta-carotene contents, and the weight loss of frozen African spinach (Amaranthus hybridus), and thereafter compared with the control. All the samples except the control were subjected to the ultrasound effects before freezing at frequency, time, and power ranges of 40-120 kHz, 10-30 min, and 50-150 W respectively. Result obtained indicated that the maximum vitamin C (99.5%) was obtained from the sample stored for 5 days under the treatment condition of 40 kHz, 50 W, and 20 min. However, the same sample retained more vitamin C within 5-20 days’ storage, while the pre-treated sample at 80 kHz, 100 W, and 10 min retained the maximum (80.9%) at 25 days of storage. The sample under the treatment condition of 80 kHz, 100 W, and 20 min lost more vitamin C (67.6, 66.6, and 59.2%) between 15-25 storage days. While for the beta-carotene, the sample with the treatment condition of 40 kHz, 50 W, and 20 min before freezing had the highest retention (99.8%) when stored for 5 days, and the same sample retained more at 10, and 15 days than others (97.6, and 92.4%). All pre-treated samples retained more beta-carotene at 25 days of storage when compared to the control with the least retention between 15-25 days. Furthermore, the least obtained content from the pre-treated samples was 64.9%, that is, a sample treated at 80 kHz, 100 W, and 20 min. The result revealed that Amaranthus hybridus was best preserved in pre-treated Amaranthus hybridus leaves. The optimum quality response occurs at 80kHz and 50 W for 30 min. This gives a vitamin C content of 31.1 mg/100g and a Betacarotene content of 10.5 mg/g at 0.694 desirability.