Stability of vitamin C in fruit and vegetable homogenates stored at different temperatures

• Vitamin C analyzed in several types of homogenized fruits and vegetables.
• Assayed after refrigerated and frozen storage (−20 °C, <−55 °C) over 1-week period.
• No change in vitamin C at <−55 °C.
• Significant losses after refrigeration or freezing at −20 °C in some foods.
• Up to 15% loss in non-acidic stored 3 days at −20 °C (17 mg/100 g in raw broccoli).
• Detailed quality control implemented and described to ensure validity of data.

Vitamin C loss was compared in homogenized raw broccoli, potatoes, spinach, strawberries, oranges, and tomatoes; baked potatoes; steamed broccoli and spinach; and pasteurized orange juice after storage under residual nitrogen under refrigeration, and frozen at conventional (−10 to −20 °C) and ultra-low (<−55 °C) temperatures for 1, 3, and 7 days. Additional foods (cantaloupe, green sweet peppers, collard greens, clementines) were monitored for 3–4 years at <−55 °C. Total ascorbic acid was quantified using high-performance liquid chromatography and detailed quality control measures. No decrease occurred in any of the foods after 7 days at <−55 °C. Under refrigeration the largest decreases were in raw spinach and broccoli, averaging (mg/100 g) 9.5 (29%) and 33.1 (29%), respectively, after 1 day and 31.0 and 77.0 after 7 days (94% and 68%, respectively). With conventional freezing, vitamin C was stable for 7 days in most of the products studied; minor losses occurred in raw spinach and broccoli after 1 day but were substantial after 3 days, 6.9 mg/100 g (23%) and 17.0 mg/100 g (15%), respectively; and 7 days (13.1 and 32.0 mg/100 g). For homogenates stored long-term at <−55 °C, vitamin C loss occurred in only cantaloupe, collard greens, and one sample of raw potatoes, all before 50 weeks.