Green microalgae derived organic nanodots used as food preservative

Spirulina platensis derived organic nanodots (ND) may be used as an alternative of chemical food preservative that can increase shelf life of food and beverages. Microalgal nanodots were isolated by the supercritical carbon dioxide extraction (SCE) method. Then SCE extract was subjected to thin-layer chromatography (TLC) and fractions were screened by a well diffusion method to identify the active compound with strong antibacterial ability. A characteristic of ND is the emitting of red colour upon the absorbance of ultra-violet (UV) light. The isolated ND is active against both Gram-positive and Gram-negative bacteria that significantly avoid their auto-aggregation. The nanodots were characterized by using TEM, UV-VIS, FTIR and NMR spectroscopy. FTIR and NMR analysis revealed the presence of hydrogen-bonded hydroxyl and amide groups. In addition, ND is applied in litchi juice as a preservative to extend the shelf life. In general, our results revealed that the sensory quality i.e. colour, aroma and overall appearance were significantly affected by duration of storage. It proves that Spirulina platensis derived organic nanodots act as a strong food and beverage preservative.