Analysis of peach fruit slices osmotically dehydrated with sorbitol and hot-air-dried over a 55-day conservation period

Abstract

Peach is a subtropical fruit with a fleshy pulp and a delicate aroma. It’s the third more commercialized fruit around the globe; though, it is perishable having a short shelf life. Different strategies are currently used to preserve its nutraceutical properties. Osmotic dehydration (OD) previous heat drying is an emergent procedure which prevents browning and the bioactive compound loss due to prolonged heating. While different sugars such sucrose can be used during OD, sorbitol is a healthier alternative. Sorbitol is naturally occurring in peach fruit and it has a reduced calorie value and a very low glycemic index, which make it ideal for diabetic persons and for consumers that are looking for a snack reduced in sugars. Previously, we showed that sorbitol can be used as osmolyte in the OD processing of peach fruit slices, rendering a healthy product. In the current work, we studied the stability over a 55-day period of dried peach slices which were osmotically dehydrated with sorbitol previous to heat drying. Flordarking peaches from San Pedro, Buenos Aires, were harvested at commercial maturity, disinfected, cut in slices and immersed in CaCl2 and ascorbic acid solutions. Then, the slices were incubated at 40°C in a 47° Brix sorbitol solution during 3 hours under stirring. Subsequent, they were dried at 58°C during 4 h until 8.3±1.0 % relative water content (RWC ). Slices were stored in a closed glass container with a supersaturated solution of sodium bromide to generate a 50 % relative humidity atmosphere. The vessel was placed in a dark chamber at 25 ˚C during 55 days. Color, fresh, and dry weights, sensory texture, antioxidant activity and total protein, glucose, sucrose, sorbitol, ascorbic acid, total phenolics compounds, carotenoids and flavonoids contents were measured at 0, 15, 33, 41, 49 and 55 days after storage. RWC of the stored slices was 27.6±1.3 %, due to humidity equilibration with that of the chamber. Slight changes in slice color were observed during storage, with 55-days stored slices being reddish and less yellow than samples collected at 0. This data agrees with a 75 % decrease in the carotenoid content in samples analyzed at day 55. Conversely, antioxidant activity, total protein, glucose, sucrose, sorbitol, ascorbic acid, total phenolic compounds, and flavonoids contents, and manual fracture, texture and cohesiveness were constant over time . After 15 days, firmness and crunchy perception was increased and accompanied with a decrease in oral breakdown. Taking together, osmotic dehydration with sorbitol before heat drying is a plausible option to dehydrate peaches slices and to generate a healthy snack for diabetic consumers that maintains its nutritional properties and bioactive compounds over at least 55 days after processing.