Aroma Profiles of Dried Citrus: Comparing Oven-Dried and Freeze-Dried Methods

Jim Crocker
27th July, 2024

Aroma Profiles of Dried Citrus: Comparing Oven-Dried and Freeze-Dried Methods

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at Zhongkai University of Agriculture and Engineering studied the aroma profiles of dried gonggans using oven- and freeze-drying methods
  • Freeze-drying preserved citrus and mandarin-like aromas better, retaining high levels of key compounds like limonene and citral
  • Oven-drying at high temperatures enhanced floral, fruity, and sweet aromas by promoting the accumulation of terpenes and generating new VOCs
Dehydration is a widely-used method for preserving the quality and extending the shelf life of fruits, including gonggan (Citrus sinensis Osb. 'Deqing Gonggan'), a Chinese citrus variety known for its unique floral, fruity, and citrus aromas. However, the impact of different drying methods on the aroma profiles of gonggans has not been well-documented. A recent study conducted by Zhongkai University of Agriculture and Engineering aimed to address this gap by analyzing the volatile organic compounds (VOCs) in gonggans subjected to oven- and freeze-drying methods[1]. In this study, researchers identified a total of 911 VOCs in dried gonggan samples. These compounds were predominantly alcohols (7.69%), aldehydes (7.03%), esters (15.38%), ketones (7.58%), and terpenoids (23.19%). Among these, 67 odorants were found to significantly contribute to the overall aroma, characterized by green, citrus, fruity, floral, and sweet notes. The major contributors to these aromas were aldehydes, esters, and terpenoids. The study found that freeze-drying was more effective in preserving the citrus and mandarin-like aromas of gonggans. This method retained high levels of compounds such as limonene, citral, β-myrcene, β-pinene, and γ-terpinene. Notably, (E,E)-2,4-decadienal had the highest relative odor activity value (rOAV) in freeze-dried gonggans, followed by (E)-2-nonenal, furaneol, (E,E)-2,4-nonadienal, and E-2-undecenal. These findings are consistent with previous research on the aroma profiles of citrus fruits, where compounds like limonene and (E,E)-2,4-decadienal were identified as key contributors to characteristic citrus aromas[2]. On the other hand, oven-drying at elevated temperatures promoted the accumulation of terpenes such as octatriene, trans-β-ocimene, cyclohexanone, copaene, and ɑ-irone. These compounds imparted a soft aroma of flowers, fruits, and sweetness to the dried gonggans. The increase in temperature during oven-drying led to the generation of new VOCs and an increase in existing ones through metabolic pathways involving phenylpropanoids, terpenoids, and fatty acids. This aligns with previous findings where drying methods influenced the volatile composition and sensory characteristics of plant materials, such as spearmint[3]. The study's findings offer valuable insights for the fruit-drying industry. By understanding how different drying methods affect the aroma profiles of dried gonggans, producers can optimize their processes to enhance the quality of their products. For instance, freeze-drying may be preferred for preserving the unique citrus and mandarin-like aromas, while oven-drying could be used to achieve a more floral and sweet profile. This research also contributes to the broader understanding of VOC biosynthesis and regulation in plants, as discussed in earlier studies[4]. In summary, the study by Zhongkai University of Agriculture and Engineering provides a comprehensive analysis of the VOCs in dried gonggans and highlights the impact of oven- and freeze-drying methods on their aroma profiles. These findings not only enhance our understanding of fruit dehydration but also offer practical applications for improving the quality of dried fruits in the industry.

FruitsNutritionBiochem

References

Main Study

1) The aroma profiles of dried gonggans: Characterization of volatile compounds in oven-dried and freeze-dried gonggan.

Published 26th July, 2024

https://doi.org/10.1016/j.foodres.2024.114716

Related Studies

2) Differentiation between Flavors of Sweet Orange (Citrus sinensis) and Mandarin (Citrus reticulata).

https://doi.org/10.1021/acs.jafc.7b04968

3) Influence of drying on the flavor quality of spearmint (Mentha spicata L.).

Journal: Journal of agricultural and food chemistry, Issue: Vol 51, Issue 5, Feb 2003

4) Biosynthesis, function and metabolic engineering of plant volatile organic compounds.

https://doi.org/10.1111/nph.12145


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