The effect of various pre-drying treatments on the subsequent quality of sun-dried tomatoes was evaluated by determining moisture, color, rehydration ratio, mold, yeast, sulfur dioxide, and/or salt content. The 4 pre-drying treatments under investigation were (1) steam blanching or (2) boiling brine blanching, followed by gas sulfuring and (3) dipping in either salt (0%, 10%, 15%, 20%) or (4) sodium metabisulfite (0%, 4%, 6%, 8%) for 0, 2.5, 5.0, and 7.5 min. Neither blanching pretreatment improved the quality of the dried product. Salt dipping resulted in significant differences in rehydration ratio, yeast, and salt. The most effective salt pretreatment conditions were a 10% or 15% salt dip for 5 min. Sodium metabisulfite dipping caused significant differences in rehydration ratio, yeast, color, and sulfur dioxide. Dipping tomatoes in 6% or 8% sodium metabisulfite for 5 min before drying established the best color. The 9 pretreatments studied were also evaluated for storage stability at 25 °C and 30% to 34% relative humidity for 3 mo.

Pre-drying treatments have been found to improve the quality of stored sun-dried tomatoes. Based on previous investigation (Part I), 5 specific pretreatments were chosen for effects on nutritional value, sensory quality, and safety before and after 3 mo of storage (25 °C and 30% to 34% relative humidity). These pretreatments included (1) direct gas sulfuring with 2.3 kg (5 lb) SO 2 ; (2) with 3.6 kg (8 lb) SO 2 ; (3) dipping in 10% salt for 5 min; (4) 8% sodium metabisulfite for 5 min; and (5) 8% sodium metabisulfite and 10% salt for 5 min. The use of SO 2 improved color, rehydration ratio, and minimized the loss of ascorbic acid and lycopene. Sodium metabisulfite dipped tomatoes had better rehydration ratio and color than gas sulfured sun-dried tomatoes. Untrained consumers ranked gas sulfured tomatoes higher than sun-dried tomatoes produced by dipping in either sodium metabisulfite alone or sodium metabisulfite plus salt.