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. 2024 Sep 27;13(19):3081.
doi: 10.3390/foods13193081.

Validation of a Passive Solar Drying System Using Pineapple

Katie Kuhn  1 , Charles Strnad  1 , Paige Bowman  1 , Keoni Young  1 , Emma Kroll  1 , Anna DeBruine  1 , Ian Knudson  1 , Michael Navin  2 , Qingsu Cheng  3 , Michael Swedish  4 , Wujie Zhang  1
Affiliations

Validation of a Passive Solar Drying System Using Pineapple

Katie Kuhn et al. Foods. .

Abstract

Wasted produce is a pertinent issue in agriculture, with billions of tons of produce going to waste even before it hits markets. Specifically, in Sub-Saharan Africa (SSA), nearly half of all produce is lost before market. To combat this, the Agricycle® passive solar drier was designed to provide a cost-effective method of drying fruit for preservation. Using a psychrometric chamber to simulate the SSA environment, vitamin C, total phenolic contents, and iron tests were conducted, along with microbial content determination, water content determination, dissolved solids testing, and color and microstructure analyses to validate passive solar drying, comparing the results to freeze-dried samples. Nutritional contents were comparable between fresh, freeze-dried, and solar-dried samples, with a loss in vitamin C (statistically significant), total phenolic contents, and dissolved solids during solar drying. The microbial analysis for solar-dried samples was below standard limits, and the water content in the solar-dried samples was ~10% w.b. (<20% w.b.) compared to ~3% w.b. of the freeze-dried samples. Although having comparable vitamin C, total phenolic contents, and iron values, freeze-dried and solar dried samples showed very different colors and microstructures based on colorimetry and SEM imaging. In conclusion, the Agricycle® passive solar drier is a promising alternative approach for food preservation.

Keywords: drying; freeze-drying; pineapple; preservation; solar drying.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Scheme 1
Scheme 1
Setup of the passive solar drying system and the drying mechanism.
Figure 1
Figure 1
Temperature and humidity profile of the psychrometric chamber for the duration of a typical 16 h run time.
Figure 2
Figure 2
Water content of fresh, freeze-dried, and solar-dried pineapple samples. * indicates significant difference (p < 0.05).
Figure 3
Figure 3
Vitamin C content of fresh, freeze-dried, and solar-dried samples. (A) raw data; (B) normalized for dry mass. * indicates significant difference (p < 0.05).
Figure 4
Figure 4
Iron content of fresh, freeze-dried, and solar-dried pineapple samples. (A) raw data; (B) normalized for dry mass. * indicates significant difference (p < 0.05).
Figure 5
Figure 5
Total phenolic content of fresh, freeze-dried, and solar-dried pineapple samples. (A) raw data; (B) normalized for dry mass. * indicates significant difference (p < 0.05).
Figure 6
Figure 6
Dissolved solids content data for fresh, freeze-dried, and solar-dried pineapple samples. (A) raw data; (B) normalized for dry mass. * indicates significant difference (p < 0.05).
Figure 7
Figure 7
ATR-FTIR spectra of fresh, freeze-dried, and solar-dried pineapple samples.
Figure 8
Figure 8
Microbial content for fresh, freeze-dried, and solar-dried pineapple samples. Dashed lines indicate the threshold for each category as permitted by several health agencies [42,43].
Figure 9
Figure 9
Color analysis data for fresh, freeze-dried, and solar-dried pineapple samples. Inserts are photos of fresh, freeze-dried, and solar-dried samples, respectively (left to right).
Figure 10
Figure 10
SEM images of freeze-dried (top panel) and solar-dried (bottom panel) pineapple samples. The magnification is 100, 500, and 1000 × from left to right, respectively.
See this image and copyright information in PMC

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