Effect of Processing Conditions on the Organosulfides of Shallot (Allium cepa L. Aggregatum Group)

Abstract

There is a growing account of the health benefits of H2S as an endogenous cell-signaling molecule. H2S from organic polysulfides, in particular, is increasingly gaining attention for their beneficial effects to cardiovascular health. Here, we studied shallot as a potential dietary source of organic polysulfides and examined the effects of processing conditions on its polysulfide profiles. Boiling, autoclaving, and freeze-drying were tested on whole and crushed shallot bulbs, analyzing their effect on the yield of organosulfides. Seventeen organosulfides, including disulfides, trisulfides, and cyclic polysulfides, were identified. Significant differences in the quantitative and qualitative profiles of organosulfides in the hydrodistilled and solvent extracted oils were observed. Freeze-drying retained the majority of the organosulfides, but the whole-autoclaved and whole-boiled shallots lost more than 95% of their organic polysulfides. Crushed-boiled and crushed-autoclaved shallot lost 76-80% of their organosulfides, likely due to the thermal sensitivity of these compounds. The organosulfide profiles are sensitive to the pH values of the processing media. In general, disulfides increased at basic pH (pH 9.0) while trisulfides and cyclic organosulfides are much higher at the acidic to neutral pH values (pH 3.0-5.0). Our results provide important information on the effects of processing conditions that are relevant for optimizing extraction of organosulfides from shallot for further studies evaluating their H2S-releasing activity.

Organosulphide profile and hydrogen sulphide-releasing capacity of garlic (Allium sativum L.) scape oil: Effects of pH and cooking

“…Our results were also in agreement with a literature report on distilled garlic oil showing favoured formation of disulphides at pH 9.0 while trisulphides were much higher at weakly acidic pH range (Yu, Wu, & Chen, 1989). Recently, we demonstrated similar trends on the pH sensitivity of polysulphides in shallot oil (Tocmo, Lin, & Huang, 2014). It has been suggested that optimal formations of trisulphides at acidic pH could be due to their stability and the stability of alliinase in this pH range under heat treatment (Yu et al, 1989).…”

Stability and extraction of bioactive sulfur compounds from Allium genus processed by traditional and innovative technologies

“…al. (2014), showed that thermal processing by both boiling and autoclaving resulted in significant losses in cyclic and acyclic organosulfides in shallot (Allium cepa L. Aggregatum Group), whilst freeze-drying retained the majority of the organosulfides, although some were found to be sensitive towards freeze-drying as well (Tocmo et al, 2014). These drying methods (air-, oven-and freeze-drying) were also shown to significantly affect the yield and composition of the essential oils obtained by hydrodistillation of the dried garlic bulbs, with freeze-drying resulting in a much higher yield of diallyl tetrasulfide and diallyl trisulfide (Dziri et al, 2014).…”

Home-cooked garlic remains a healthy food

“…There are few reports regarding the analysis of these compounds in cooked garlic samples (Cavagnaro, Camargo, Galmarini, & Simon, 2007;Kim, Wu, Kobayashi, et al, 1995;Kim, Wu, Kubota, & Kobayashil, 1995;Yu & Wu, 1994;Yu et al, 1993). Works reported have been based on the analysis of OSCs by GC-MS (Artacho Martin-Lagos, Olea Serrano, & Ruiz Lopez, 1995;Tocmo, Lin, & Huang, 2014;Yan, Wang, & Barlow, 1992, using Lickens-Nickerson distillation and solvent extraction techniques (Kim, Wu, Kobayashi, et al, 1995;Yu et al, 1993Yu & Wu, 1994;Yu, Wu, & Chen, 1989;Yu, Wu, & Liou, 1989). It is worth emphasizing that those sample preparation techniques, as well as the subsequent analysis by GC, are inadvisable (Block, Putman, & Zhao, 1992).…”