Elsevier

Journal of Functional Foods

Volume 30, March 2017, Pages 254-259
Journal of Functional Foods

Organosulphide profile and hydrogen sulphide-releasing activity of garlic fermented by Lactobacillus plantarum

https://doi.org/10.1016/j.jff.2017.01.001Get rights and content

Highlights

  • A method of fermenting garlic using Lactobacillus plantarum Lp-115 as starter culture.

  • Fermentation decreases allicin and vinyl dithiins, but increased the concentration of diallyl polysulphides.

  • Blanching significantly decreases organosulphide content and H2S-releasing activity of blanched-fermented garlic.

  • Fermentation without blanching retains the H2S-releasing activity of garlic.

Abstract

Blanched and unblanched garlic were fermented using L. plantarum for investigation of organosulphide profiles, hydrogen sulphide-releasing activity, pH, titratable activity and microbial growth. Both raw and blanched garlic preparations allowed growth of L. plantarum with corresponding lowering of pH below 4.0 and an increase in titratable acidity from an initial value of less 0.05% to 0.3 and 0.5%, respectively. Fermentation, alone, decreased allicin and vinyl dithiins, but increased the concentration of DATS. The H2S-releasing activity, expressed as DATS-E (mmol DATS/g oil), of raw-fermented (2.91) garlic was not significantly different to that of raw (4.74) garlic, but values in blanched (0.41) and blanched-fermented (0.71) samples significantly decreased. Reductions in DATS-E values in blanched and blanched-fermented garlic corresponded well with the negative effect of blanching on the organosulphide concentrations of the products. Fermentation with L. plantarum retains H2S-releasing activity by increasing DATS, despite notable losses in allicin and allicin transformation products.

Introduction

Hydrogen sulphide (H2S) is a gaseous molecule endogenously produced by the action of the enzyme cystathionine-γ-lyase (CSE) on cysteine in smooth muscle tissues (Zhao, Zhang, Lu, & Wang, 2001) and is currently a subject of intense research. This is mainly because this obnoxious gas, long considered as a toxic pollutant, has shown important physiological and pharmacological functions, including regulation of cardiovascular functions (Shen et al., 2015, Snijder et al., 2015, Szabó et al., 2011) and anti-cancer activities (Feng et al., 2015, Gemici et al., 2015, Zhao et al., 2015). The discovery of the important biological roles of H2S has prompted investigations on ‘H2S donors’, which include both synthetic (Rose et al., 2015, Song et al., 2014, Whiteman et al., 2015, Zhao et al., 2015) and natural donors (Liang et al., 2015, Shin et al., 2007, Tsai et al., 2015). Garlic (Allium sativum) is thus far the only well-known natural dietary source of H2S donors. It is proposed that the biological conversion of organopolysulphides to H2S may explain the beneficial effects of high garlic consumption (Benavides et al., 2007, Predmore et al., 2012).

The main step during garlic fermentation is blanching, which was needed for the purpose of destroying alliinase, the enzyme in garlic that converts sulphur-containing precursors to pungent-smelling organosulphur compounds, including thiosulphinates and oil-soluble polysulphides (Rejano, Sanchez, De Castro, & Montano, 1997). In addition, blanching allows abundant growth of the starter culture. Beato, Sánchez, De Castro, and Montaño (2012) found that blanching did not affect the organosulphur compounds in garlic, they observed negative effect of the fermentation. Alliinase is thermally sensitive (Jansen, Muller, & Knobloch, 1989). Hence, one might expect that blanching is detrimental to the generation of important garlic polysulphides such as diallyl trisulfide (DATS) and diallyl disulphide (DADS).

To our knowledge, there is no published report on the effect of fermentation with or without blanching on the organopolysulphide content of fermented garlic and its H2S-releasing activity. The growing interest on the role of organosulphides from dietary sources as potential H2S donors prompted us to investigate the effect of fermentation on the main bioactive organosulphur components of garlic. Here, we report garlic fermentation by a new strain of probiotic lactic acid bacteria, L. plantarum Lp-115. We monitored changes on the organosulphide contents and evaluated the effect of fermentation on garlic’s H2S-releasing activity.

Section snippets

Materials

White garlic was purchased from a local market in Singapore. DADS (80%), dimethyl sulphoxide, and anhydrous sodium sulphate (Na2SO4) were purchased from Sigma-Aldrich (Singapore). DATS was purified by distillation from a mixture of DATS and DADS. Analytical grade hexane, diethyl ether, and dichloromethane were obtained from Merck Pte Ltd (Singapore). Dulbecco’s Modified Eagle Medium (DMEM) was purchased from HyClone Laboratories, Inc. (Logan, UT, USA). Fetal bovine serum (FBS) was purchased

Results and discussion

Garlic contains large amount of organosulphides and some of them may have anti-microbial activity and negatively influence fermentation by LAB. Therefore, we tested the fermentation related parameters to ensure starter culture used can grow well. We found that. for unblanched-fermented garlic, LAB population reached a maximum LAB count at day one (Fig. 2) of fermentation from an initial population. This was followed by a slight decrease at day 3 and remaining at the same level until day 9. The

Acknowledgment

Authors thank the Agency of Science, Technology and Research (A∗Star) of Singapore for financial support (grant number: 112 177 0036) and support of a Grant (grant number: BY2014139) from Jiangsu Province, China.

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      Data differences were determined using one-way analysis of variance (ANOVA), and a p value smaller than 0.05 was regarded as significantly different. We have defined a unit DATS-E, which compares the H2S releasing capacity of a sample to that of DATS, a widely acknowledged organic H2S donor from garlic oil (Liang, Wang, et al., 2015; Tocmo et al., 2017). The usage of DATS-E enables us to compare results among different batches.

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