Effect of blanching conditions on nutritional and bioactive properties of Kappaphycus Alvarezii

The conventional sun drying of Kappaphycus alvarezii often results in quality deterioration, restricting its food applications beyond carrageenan production. Since seaweed farming is a low-cost livelihood for coastal communities, there is a need for simple and affordable pre-treatments that farmers can easily adopt to preserve and improve product quality. To address this, hot water blanching was investigated as a pre-treatment strategy. Blanching seaweed at 70 °C for 60 s was found as the optimal condition for improving nutritional quality, whereas 60 °C for 30 s was the most effective condition for enhancing antioxidant properties. Blanching (70 °C for 60 s) produced a 3 h reduction in drying time with lesser moisture content, increased fat (1.89%), carbohydrate (46.09%), and crude fiber (6.76%) content without compromising protein levels. Lightness improved by 39.44%, mitigating negative sensory impacts and enhancing suitability for food formulations. Although some mineral leaching occurred, essential minerals such as potassium, magnesium, and manganese remained within the Indian Council of Medical Research recommended daily allowance limits. Sodium decreased to a safer dietary level, while phosphorus, calcium, copper, iron, and zinc levels increased, enriching the overall mineral profile. The blanched seaweed (60 °C for 30 s) showed a 64.22% increase in 2, 2-diphenyl-1-picrylhydrazyl radical scavenging activity, 120.83% in ferric-reducing antioxidant power, and 143.73% in total antioxidant activity. These improvements were linked to greater retention of betulin, a potent antioxidant terpenoid, confirmed through high-resolution liquid chromatography–mass spectrometry. These findings indicate that blanching induces temperature and time-dependent enhancement in the quality of K. alvarezii, supporting its application in functional foods.