Preparation and Evaluation of Nanoliposomes Containing green tea Extract and Investigating its Efficacy in Extending the Shelf Life of Fresh Orange and Pomegranate Juices

Green tea leaves have high contents of phenolic compounds which has strong antioxidant properties but can have bitter taste which makes it less useful in food applications. Encapsulation in nanoliposomes could mask undesirable taste of green teas components and protect them against processing and storage. The objective of this study was to: 1) produce and evaluate physical properties of green tea extract (GTE) nanoliposomes using ethanol injection method; and 2) to incorporate them in different concentrations to fresh orange and pomegranate juices to preserve their quality upon storage. Particle size distribution and average diameter of GTE nanoliposomes were determined using dynamic light scattering method. Zeta potential was determined and encapsulation efficiency was evaluated using determination of total phenolic compounds of GTE in nanoliposomes. By incorporating more concentration of GTE in nanoliposomes their particle size increased from 67.7 nm for lower concentration to 370 nm for higher concentration. The average particle size of larger nanoliposomes (>100 nm) was increased upon storage time. Zeta potential data ranged from -20 to -25 mV indicating that all GTE nanoliposomes possess negative electrostatic charges promoting their stability by preventing them from coalescence and flocculation. Encapsulation efficiency was significantly (p<0.05) reduced by increasing in GTE concentrations in nanoliposomes. The nanoliposome system could preserve GTE compounds from possible oxidation and deterioration during processing and storage when used in formulation of orange and pomegranate juices. It was shown that the nanoliposome encapsulation of GTE improved its beneficial properties including antioxidant activities. Variations in GTE concentration as well as type of capsulation were critical in some of the parameters studied, i.e. pH, acidity, ascorbic acid and anthocyanins content. Higher GTE concentrations maintained the quality of fresh orange and pomegranate juices better than lower concentrations. Different concentrations of GTE in both non-capsulated and capsulated forms did not influence pH and acidity of orange and pomegranate juices. Acid ascorbic contents of both orange and pomegranate juices was significantly and negatively influenced by storage time. However, by incorporating GTE in nanoliposomal form to both orange and pomegranate juice, destruction of acid ascorbic was reduced during storage compared to control samples. In pomegranate juice the same trend was seen for anthocyanin content. By incorporation GTE nanoliposomes at concentrations of 300 ppm more anthocianins was preserved upon a long storage days compared to control. Concluding, the methodology used in this study to produce GTE nanoliposomes and incorporating them into orange and pomegranate juices could meaningfully preserve vit. C and anthocyanin contents of the juices during long storage days, while keeping their other physicochemical properties constant. Overall, this paper showed a possible use of GTE as a natural preservative ingredient to extend the shelf-life of fresh orange and pomegranate juices.