Effect of Freeze-Thaw Cycles on Juice Properties, Volatile Compounds and Hot-Air Drying Kinetics of Blueberry.

Lin Zhu,Yushuang Lu,Sheng Fang,Fubin Lin,Shiyi Tian,Jie Chen,Xianrui Liang

doi:10.3390/foods10102362

Lin Zhu, Yushuang Lu + Show 5 more

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https://doi.org/10.3390/foods10102362

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Abstract

This paper studied the effects of freeze-thaw (FT) cycles on the juice properties and aroma profiles, and the hot-air drying kinetics of frozen blueberry. After FT treatment, the juice yield increased while pH and total soluble solids of the juice keep unchanged. The total anthocyanins contents and DPPH antioxidant activities of the juice decreased by FT treatments. The electronic nose shows that FT treatments significantly change the aroma profiles of the juice. The four main volatile substances in the fresh juice are (E)-2-hexenal, α-terpineol, hexanal and linalyl formate, which account for 48.5 ± 0.1%, 17.6 ± 0.2%, 14.0 ± 1.5% and 7.8 ± 2.7% of relative proportions based on total ion chromatogram (TIC) peak areas. In the FT-treated samples, the amount of (E)-2-hexenal and hexanal decreased significantly while α-terpineol and linalyl formate remained almost unchanged. Repeated FT cycles increased the ethanol content and destroyed the original green leafy flavor. Finally, the drying kinetics of FT-treated blueberries was tested. One FT treatment can shorten the drying time by about 30% to achieve the same water content. The Deff values of the FT-treated sample are similar, which are about twice as large as the value of the fresh sample. The results will be beneficial for the processing of frozen blueberry into juice or dried fruits.

Highlights

Blueberry is widely grown all over the world and its production has largely increased in recent years [1]
Yan et al [9] found that aroma deterioration during subsequent shelf life after cold storage was more fatal to the blueberry flavor
To the best of our knowledge, there are no studies on the effects of multiple FT cycles on the physicochemical properties of frozen blueberry, especially focus on, aromatic compounds and drying kinetics

Summary

Introduction

Blueberry is widely grown all over the world and its production has largely increased in recent years [1]. Due to seasonality and short shelf life, approximately 50% of blueberries are processed into food products such as juice and dry fruits [2]. Most of the blueberries used for juice processing and drying are frozen fruits. During storage and cold chain transportation, frozen blueberries might be subjected to several freeze-thaw (FT) cycles [3]. The ice crystal formed in FT treatments facilitates the rupture of fruit cell walls and changes the texture and flavor during the thawing process. Yan et al [9] found that aroma deterioration during subsequent shelf life after cold storage was more fatal to the blueberry flavor. To the best of our knowledge, there are no studies on the effects of multiple FT cycles on the physicochemical properties of frozen blueberry, especially focus on, aromatic compounds and drying kinetics

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