The Use of a Thermal Process to Produce Black Garlic: Differences in the Physicochemical and Sensory Characteristics Using Seven Varieties of Fresh Garlic.

Jan Bedrníček,Eva Samková,Ivana Laknerová,Priscila Probio De Moraes,Pavel Smetana,Naděžda Vrchotová,Markéta Jarošová,Jan Tříska,František Lorenc,Jaromír Kadlec

doi:10.3390/foods10112703

Abstract

Black garlic (BG) is a product originating from fresh garlic (FG) and substantially differs in many aspects from FG due to the process called ageing. During this thermal process, the health-promoting properties of FG are enhanced, and the sensory traits are altered. However, very little is known about how the physicochemical properties of different FG varieties affect these properties of BG. Thus, the aim of this study was to investigate the influence of seven FG varieties subjected to the thermal process on the physicochemical parameters of BG. To prepare the BG samples, a fifteen-day ageing process involving a temperature gradient ranging from 30 to 82 °C was used. It was found that the antioxidant activity, the total polyphenol content, and the total soluble solids increased during ageing, while the pH level, moisture content, and lightness decreased in all the garlic varieties. The varieties of garlic differed in the studied traits significantly, both before (FG) and after ageing (BG). In the sensory analysis, significant differences between the BG varieties were observed only in the pleasantness of texture, while the remaining sensory descriptors (pleasantness of color, odor, taste and intensity of the garlic aroma, and overall acceptability) were not affected by variety. The correlations suggest that most of the FG’s studied parameters in this study do not correlate with the properties of BG and cannot be used for the prediction of the quality of BG. Additionally, HPLC-MS/MS analysis revealed substantial changes in the composition of low molecular compounds.

Highlights

Antimicrobial activity was investigated by Botas et al [2] who found that Black garlic (BG) had stronger antimicrobial activity than fresh garlic (FG)
It is evident that the studied parameters were positively affected by the ageing process in all varieties, mainly the antioxidant activity, and the samples of BG obtained favorable attributes
There is a significant influence of variety on the physicochemical parameters of BG, namely on moisture, total soluble solids and total polyphenol content, pH, antioxidant activity, texture, and color

Summary

Introduction

BG is botanically Allium sativa L., it differs from fresh garlic (FG) in many aspects It is processed using higher temperatures, ranging between 60–90 ◦ C, with approximately 80% relative air humidity for a long period of time (10–90 days) without using any other ingredients or additives. This thermal process is called ageing and during this process the fresh white garlic gains many new properties, such as enhanced biological activity, especially antioxidant activity, and altered sensory properties because the FG’s color turns from white to black, the texture changes to very soft or jelly-like, and the taste is very mild with sweet and sour tones [1]. Antimicrobial activity was investigated by Botas et al [2] who found that BG had stronger antimicrobial activity than FG

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