Low-frequency ultrasound-assisted preparation of taurine-loaded nanoemulsion and its preservative effect on fresh-cut pitaya.

In this study, a taurine-loaded nanoemulsion was prepared using low-frequency ultrasound at 20 kHz for 20 min, and its preservative effects on fresh-cut pitaya was evaluated. The optimal preparation conditions were 400 W ultrasonic power and 1.0% taurine, which produced a nanoemulsion with a mean particle size of 112.58 nm, a polydispesity index of 0.17, a zeta potential of -35.84 mV, an encapsulation efficiency of 85.27%, and good stability for 28 days at 4 °C. Compared with control, free taurine, and blank nanoemulsion treatments, the taurine-loaded nanoemulsion (T-NE) significantly delayed quality deterioration during 8 days of storage at 4 °C. On day 8, the treated fruit showed a weight loss of 8.24%, a firmness loss of 5.18 N, maintained higher soluble solids (10.62 °Brix), a total phenolic content of 65.43 mg/100 g, and DPPH radical scavenging activity of 75.38%. The treatment also enhanced superoxide dismutase and catalase activity, inhibited polyphenol oxidase activity, lowered malondialdehyde accumulation (4.68 nmol/g), and reduced the total viable count and mold and yeast count to 4.73 log CFU/g and 3.65 log CFU/g, respectively. These findings indicate that the taurine-loaded nanoemulsion can prolong the refrigerated shelf life of fresh-cut pitaya and may have broader applications in fruit and vegetable preservation.