Effects of acidity and molecular size on bacteriostatic properties of beer hop derivates

Blanco, Carlos A.; Rojas, Antonio; Nimubona, Dieudonné

doi:10.1016/j.tifs.2006.09.005

Cited by 29 publications

(19 citation statements)

References 37 publications

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“…4 This bacteriostatic activity of hop bitter acids has been assigned to hydrophobic interactions of prenyl groups, present in α-and β-acid structures, with the bacterial cell walls. 6,8 Lupulones have been shown to be more active than humulones and isohumulones because β-acids have three prenyl side chains rather than two in the α-and iso-α-acids. 5,11,12 Several technological applications have recently been developed to explore the bacteriostatic activity of lupulones, for example, the use of β-acids in the control of bacterial activity during extraction of sugar beet and in industrial ethanol production, replacing conventional antibiotics such as penicillin.…”

Section: ■ Introductionmentioning

confidence: 99%

On the Reaction of Lupulones, Hops β-Acids, with 1-Hydroxyethyl Radical

Almeida

Nascimento

Cardoso

2012

J. Agric. Food Chem.

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Lupulones, hops β-acids, are one of the main constituents of the hops resin and have an important contribution to the overall bacteriostatic activity of hops during beer brewing. The use of lupulones as natural alternatives to antibiotics is increasing in the food industry and also in bioethanol production. However, lupulones are easy oxidizable and have been shown to be very reactive toward 1-hydroxyethyl radical with apparent bimolecular rate constants close to diffusion control k = 2.9 × 10(8) and 2.6 × 10(8) L mol(-1) s(-1) at 25.0 ± 0.2 °C in ethanol-water solution (10% of ethanol (v/v)) as probed by EPR and ESI-IT-MS/MS spin-trapping competitive kinetics, respectively. The free energy change for an electron-transfer mechanism is ΔG° = 106 kJ/mol as calculated from the oxidation peak potential experimentally determined for lupulones (1.1 V vs NHE) by cyclic voltammetry and the reported reduction potential for 1-hydroxyethyl radical. The major reaction products identified by LC-ESI-IT-MS/MS and ultrahigh-resolution accurate mass spectrometry (orbitrap FT-MS) are hydroxylated lupulone derivatives and 1-hydroxyethyl radical adducts. The lack of pH dependence for the reaction rate constant, the calculated free energy change for electron transfer, and the main reaction products strongly suggest the prenyl side chains at the hops β-acids as the reaction centers rather than the β,β'-triketone moiety.

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Section: ■ Introductionmentioning

confidence: 99%

On the Reaction of Lupulones, Hops β-Acids, with 1-Hydroxyethyl Radical

Almeida

Nascimento

Cardoso

2012

J. Agric. Food Chem.

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“…1997). Hop acids are believed to affect bacteria by disrupting the proper functioning of the membrane (Teuber and Schmalrek 1973) and by reducing the intracellular pH (Simpson and Hammond 1991; Blanco et al. 2006).…”

Section: Introductionmentioning

confidence: 99%

Protective effect of hop ?-acids on microbial degradation of thick juice during storage

Justé

Krause

Lievens³

et al. 2007

J Appl Microbiol

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Aims: This study assessed the value of a commercial alkaline solution of hop β‐acids (HBA) for prevention of microbial degradation of thick juice, a concentrated intermediate product in the production of beet sugar. Methods and Results: The antimicrobial effect of different concentrations of HBA against microbial degradation of thick juice was tested in a pilot‐scale storage experiment. Chemical, biochemical and microbial parameters were monitored during thick juice storage. Thick juice degradation, indicated as a decrease in pH, was generally accompanied by an increase in the count of fastidious bacteria (FB) on Columbia Agar with Sheep Blood (CAwSB), which were mainly identified as Tetragenococcus halophilus. Addition of HBA delayed juice acidification and the development of FB in a concentration‐dependent manner. The susceptibility of FB to HBA was determined by plating degraded thick juice (FB > 105 CFU ml−1) on CAwSB plates with different concentrations of HBA (0–160 ppm). None of the HBA concentrations tested reduced the number of FB colonies formed, but increasing HBA concentrations extended the lag time of colony formation. Conclusions: HBA produce no measurable bactericidal effect, but retard the development of FB in thick juice. Moreover, HBA do not prevent the thick juice from deteriorating, but significantly delay its degradation. Significance and Impact of the Study: These results indicate that adding a commercially available HBA formulation can prolong the storage life of thick juice in the sugar industry, although degradation cannot be eliminated. Future research will focus on the detailed characterization of FB consistently isolated from degraded thick juice and on determining their role in thick juice degradation.

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“…[35] Iso-humulones from hops have indicated certain levels of antibacterial activity on most gram-positive bacteria. [113][114][115][116] However, their positive role in the human body is still questionable. Lactic acid bacteria (gram-positive) are the most abundant microbial contaminants in beer.…”

Section: Downloaded By [Rutgers University] At 10:01 10 April 2015mentioning

confidence: 99%

Health-Related Aspects of Beer: A Review

Sohrabvandi

Mortazavian

Rezaei

2012

International Journal of Food Properties

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Beer is consumed worldwide and is a universally popular beverage. This is due to its sensory, nutritional, and medicinal properties. Surveys have shown that light to moderate consumption of alcoholic beverages (including beer) with relatively low alcohol contents can provide various favorable impacts on humans' health, including nutritional benefits, anti-mutagenic and anti-carcinogenic effects, reduction of cardiovascular disease (cardioprotective effect), hypolipidemic effect, immune system stimulation, anti-osteoporosis effect, and reducing risk of dementia. On the contrary, consumption of these beverages in excessive amounts results in some heath disorders, such as allergy induction, increase in the plasma concentration of uric acid, mutation and cancer induction, increase in the risk of dementia, obesity, and some social misbehaviors. Health-related aspects of beer (both positive and negative impacts) have been comprehensively reviewed in this article.

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Effects of acidity and molecular size on bacteriostatic properties of beer hop derivates

Cited by 29 publications

References 37 publications

On the Reaction of Lupulones, Hops β-Acids, with 1-Hydroxyethyl Radical

On the Reaction of Lupulones, Hops β-Acids, with 1-Hydroxyethyl Radical

Protective effect of hop ?-acids on microbial degradation of thick juice during storage

Health-Related Aspects of Beer: A Review

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