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Title: Improving the sun drying of apricots (Prunus armeniaca) with photo-selective dryer cabinet materials

item Milczarek, Rebecca
item AVENA-MASCARENO, ROBERTO - California State University
item ALONZO, JEROME - National Institute Of Agronomy, Food Science And Environment (AGROSUP)
item FICHOT, MELISSA - School Of Engineers Of Purpan

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2016
Publication Date: 9/21/2016
Citation: Milczarek, R.R., Avena-Mascareno, R., Alonzo, J., Fichot, M.E. 2016. Improving the sun drying of apricots (Prunus armeniaca) with photo-selective dryer cabinet materials. Journal of Food Science. 81(10):E2466-E2475.

Interpretive Summary: Certain fruits, such as apricots, are commonly sun-dried into healthful products by both large and small processors. Some processors perform shade-drying, in which the fruit is not directly exposed to sunlight. This practice is thought to preserve some of the nutrients in the fruit, but it prolongs the drying process. This study looked at how drying cabinet lid materials that transmitted and blocked different wavelengths from sunlight affected the drying rate and quality of the dried apricots. The 5 tested lid materials ranged from totally transparent (transmitting all light from the sun) to totally opaque (all sunlight was blocked). The choice of lid material had a strong effect on drying rate; the more wavelengths the material transmitted, the higher the air temperature inside the cabinet, and the faster the drying rate. In fact, the length of time to produce completely dried apricots could be reduced from 3-4 days (shade drying) to 1-2 days (drying with clear or ultraviolet-light-blocking materials). The cabinet material did not have an effect on brightness of the fruit or Vitamin C content. The infrared-blocking material caused the greatest loss of red color, though the reason for this and the impact on the dried fruits’ desirability are unknown. The clear material resulted in dried apricots with slightly lower antioxidant activity than those dried under opaque black or infrared-blocking materials. So, ultraviolet-blocking material is the best choice for fast-drying apricots while retaining antioxidant activity.

Technical Abstract: Photo-selective materials have been studied for their effects on the pre-harvest quality of horticultural crops, but little work has been done on potential post-harvest effects. The aim of this work was to characterize the effects of 5 different photo-selective acrylic materials (used as the lid to a single-layer sun drying cabinet) on the drying rate and quality of apricots (Prunus armeniaca). Photo-selective cabinet materials that transmit light in the visible portion of the solar spectrum accelerate the apricots’ drying rate in both the early period of drying and the course of drying as a whole. These materials do not significantly affect the measured quality metrics during the first day of sun drying. However, when drying is taken to completion, some minor but significant quality differences are observed. Infrared-blocking material produces dried apricot with lower red color, compared to clear, opaque black, and ultraviolet-blocking materials. Clear material produced dried apricot with significantly lower antioxidant activity, compared to black and infrared-blocking materials. Using appropriate photo-selective drying cabinet materials can reduce the required sun drying time for apricots by 1-2 days, compared with fully shaded drying. Ultraviolet-blocking material is recommended to maximize drying rate and minimize quality degradation.