Physicochemical and Structural Properties of Spray-Dried Sweet Lemon Juice as Affected by Polymeric Additives and Spray Drying Operating Conditions

Abstract

Citrus limetta commonly known as sweet lemon or Mosambi (in India) is one of the citrus fruits that provide high nutritional value. The d-limonene is a major component present in the Mosambi fruit, which possesses wide-ranging medicinal properties such as anticancer, antidiabetic, digestive aid, gastroesophageal reflux relief, immunity booster, and treating skin conditions. The Mosambi fruit is rich in vitamin C; hence, it has high antioxidant activity, making it a popular house remedy. The sweet lemon fruit is seasonal and easily spoiled due to the fruit's acidic pH range. A dehydrated juice product would be ideal for long-term preservation. Spray drying is the preferred technique for many thermally sensitive materials. The process removes excess moisture quickly and safely, thus improving the shelf life of the final product. The spray dried powder can be then reconstituted with water for consumption. In this study, we employed the spray drying method to conserve sweet lemon juice. We utilized three different additive drying aids, namely maltodextrin, gum Arabic, and whey protein. The inlet temperature and feed flowrate were altered, and different combinations of the spray drying process were performed. The powder properties such as color, water activity, moisture content, total titrable acidity, water solubility index, bulk and true densities, and porosity were analyzed. The biochemical properties such as the antioxidant activity, total phenol content, and vitamin C content were also calculated. The SEM and FTIR results showed the powder structure and the presence of different functional groups, respectively. On the whole, the experimental results support a spray drying process of an inlet temperature of 150°C with polysaccharide-based drying aids (maltodextrin and gum Arabic) producing a powder better than with whey protein. The spray dried sweet lime powder with maltodextrin was uniform under SEM and manifested the following parameters: water activity a_w was less than 0.37, while moisture range X_w was 1.98–3.1, suggesting microbial safety and extended shelf life. It has also retained vitamin C (AAC > 35 mg/100 mL) and showed higher antioxidant activity (DPPH > 70%) along with other quality functional properties; thus, it is considered a beneficial antioxidant-rich powder.