УДК 664.1.031

Nechipor T.N., Teterina S.N.

National University of Food Technologies (Kiev, Ukraine)

Possibility of using the hop β-acids in the sugar industry

Hops have been used in the brewing of beer for decades, and the bacteriocidal β-acids are derived from the hop plant Humulus lupulus which is a perennial climbing plant of the hemp family Cannabinaceae. The lupulin glands of hops flowers contain three important groups of natural products, the α-acids, the β-acids, and essential oils. These compounds are extracted from the hop flowers using liquid carbon dioxide to give a hop extract containing about 50% α-acids, 20% β-acids, and 5% oil. These three components in the hop extract are separated and the β-acids are used to make the anti-bacterial agent [4].

A number of early investigators from 1948-1968 noted that the hop resins act mainly on gram-positive bacteria e.g. Bacilli, Corynebacteri, Diplococci, Mycobacteria, Streptococci, Lactobacilli, and Streptomycetes. While gram-negative bacteria and other microorganisms (such as yeasts and molds) were either resistant or only affected by high concentrations of the hop resins [5]. This is due to the difference in the nature of the cell wall of gram-positive and gram-negative bacteria. Gram-positive bacteria are characterized by a peptidoglycan cell wall which accounts for 40 to 90% of the weight of the wall. However, in gram-negative bacteria the peptidoglycan content of the wall is relatively low (1-10% of the total weight of the wall) and is confined to the innennost rigid layer of the wall. The so-called outer membrane layer of the gram-negative cell wall contains proteins, lipopolysaccharides, and lipoproteins [2]. The bacteriocidal nature of β-acids seems to be dependent on the hydrophobic properties of the cell wall [5], and the resistance of the gram-negative bacteria is probably due to the presence of the phospholipid outer membrane [2].

Today an alkaline solution of hop β-acids is used in sugar industry under the trademark «BetaStab», because most of the known bacterial species, growing in hot juices of beet sugar factories, are gram-positive or at least sensitive against hop β-acids. The detrimental effects of bacteria in the extraction process have been well documented throughout the industry. The negative aspects of a microbial infection are not limited to sugar loss alone. The by-products of microbial activity adversely affect purification, evaporation, and crystallization of the sugar syrups [1].

Beta Stab 10A is a 10% aqueous alkaline solution of hop β-acids. The whole process of making a commercial product Beta Stab 10A uses simple inorganic food grade chemicals and water giving a 100% natural product [2]. This bacteriocide acts on the cell wall of bacteria and prevents the transport of sugar into the cell. In recent decades, scientific papers explained the effect of hop acids on bacteria as a damaging effect on the function of the bacterial membrane [5] and as lowering of the intracellular pH value [3]. No health hazards for β-acids are known and therefore they have GRAS (generally regarded as safe) status [4]. Hop β-acids have turned out to be very effective against formation of NO₂ and anaerobic infections in tower extractors, which are often operated intentionally with lactic acid fermentation. Hop β-acids have additionally proved effective in the field of thick juice storage [3]. Natural antibacterials derived from hops represent a valuable alternative, when conventional disinfectants are abandoned.

Hop β-acids have been used as a biocide in the sugar industry in Europe and United States successfully for several years [2]. There is a need for laboratory studies and factory trials, followed by the prospect of using hop β-acids for local businesses as a cost-effective alternative to known biocides, including formalin, in domestic enterprises.

References

1. Fowers M. The Bactericidal Effect of Hop Derived β-acids // ASSBT-Proceedings from the 31st Biennial Meeting at Vancouver, BC (28 Feb. –3 March 2001). – 2001. – p. 79–84.

2. Hein W. 10 years' experience with natural antibacterials within Agrana / W. Hein, G. Pollach, F. Emerstorfer // Zuckerindustrie 131. – 2006. – №7. – p. 477-491.

3. Pollach G. Application of hop β-acids and rosin acids in the sugar industry/ G. Pollach, W. Hein, D. Beddie // Zuckerindustrie 127. – 2002. – №.12. – p. 921–930.

4. Samaraweera I. S. Bench studies and factory trials with the use of the beta hop acid Beta Stab 10A / I. S. Samaraweera, L. Buschette, D. L. Rheault, D. Noble // Zuckerindustrie 128. – 2003. – №32. – p. 103-124.

5. Teuber M. Membrane Leakage in Bacillus subtilis 168 Induced by the Hop Contituents Lupulone, Humulone, Isohumulone and Humulinic acid / M. Teuber, A.F. Schmalreck // Arch. Mikrobiol. – 1973. – №94. – p. 159-171.