Quality and Color Parameters of Dried Chili and Chili Powder Pretreated by Metabisulfi te Soaking with Different Times and Concentrations

Abstract

The soaking process of chili in a sulfi ting solution is important for enhancing the storage stability of dried chili and chili power. After processing, the sulfi te residues play an important role in determining product quality during storage. Chili Jinda variety (Capsicum annuum L.) was selected to investigate the sulfur dioxide (SO2) content after soaking fresh pods in 200, 1,000 and 2,000 mg.kg-1 sodium metabisulfi te (Na2S2O5) for 30, 60 and 120 min. The results revealed that the SO2 content of soaked chili increased with increasing Na2S2O5 concentration and soaking time (P < 0.05). Thermal treatments from blanching and drying reduced the SO2 residues in blanched and dried chili. The moisture content and water activity of dried chili were about 7.3–8.0% and 0.31–0.34, respectively. The residual SO2 contents in dried chili increased (P < 0.05) with both increasing soaking time (up to 60 and 120 min) and Na2S2O5 concentration (1,000 and 2,000 mg.kg-1) with values below 15 mg.kg-1 in all treatments. The total color difference (∆E*) decreased with increasing Na2S2O5. Chili powder treated with a Na2S2O5 concentration of at least 1,000 mg.kg-1 exhibited lower ∆E* values than those untreated samples after storing at 40 ºC for 30 d. A linear relationship with negative slope between ∆E* and the residual SO2 was observed in both dried chili and stored chili powder. The results suggest that at least 1,000 mg.kg-1 Na2S2O5 with a soaking time of at least 30 min could retard the changes in chili powder color changes during processing and storage.