Quality Evaluation of Prepared Wolfberry with Sodium Sulfite Impregnation under Hot Air Drying

Objective: In this paper, a wolfberry sample with 0.5% sodium sulfite impregnation was prepared under hot air drying processing. Here, sodium sulfite was applied in above-mentioned process as the known antiseptic and antibacterial food additive in order to prevent from the adhesion, discoloration and deterioration of wolfberry during long-term storage. Methods: Afterwards, the quality and safety of the prepared wolfberry were evaluated by multiply indicators, such as the sensory, pH value, the content of Lycium barbarum polysaccharides (LBPs), sulfur dioxide residue, total flavonoid content, heavy metal residues and in vitro antioxidant activities. At the same time, the inhibition effect of sugar fermentation of the prepared wolfberry at a hot and humid environment was also investigated. Results: Compared with the control, the wolfberry impregnated with sodium sulfite possessed excellent physical appearance and obvious inhibition ability of sugar fermentation. Furthermore, the SO₂ residuals 77 mg/kg and the content of heavy metals (Pb: 0.080 mg/kg; As: 0.076 mg/kg and Cd: 0.024 mg/kg) in processed wolfberry samples were exclusively conformed to the limit of the current Chinese pharmacopoeia and the relevant national standard. And the LBPs of wolfberry only lost a bit up to 2.08%. Moreover, taking V_C as a reference, the IC₅₀ values of ABTS free radical scavenging rates of LBPs and total flavonoids in the control and samples were 285.6, 322.1, 92.17 and 93.74 µg/mL respectively, as well as 1090, 1468, 181.9 and 182.7 µg/mL for IC₅₀ values of DPPH free radical. The in vitro antioxidation experiments showed that the LBPs and total flavonoids of the prepared wolfberry maintained good antioxidant activities. Conclusion: The processed wolfberry adopting sodium sulfite impregnation under hot-air drying showed the outstanding characteristics of excellent quality, long-term storage resistance and safe consumption.