7.2.2
Alternative uses of hops
For alternative applications, not only the cones but also the rest of the hop plant can be used. The inner, wooden parts of the hop bine, for instance, are known as shives or shoves. They have excellent insulation properties and mechanical strength, which makes them well suited as a material for insulation. They can also be turned into molded parts for such applications as automotive door panels. To date, however, no such applications exist on a large scale. As for cones, the antimicrobial properties of their bitter acids are of special interest for alternative uses. Even in catalytic quantities (0.001 to 0.1% by weight), they reveal their antimicrobial and preservative effectiveness, in ascending strength from iso-alpha acids, to alpha acids, to beta acids polar (Figure 7.6).
Figure 7.6: Sequence of antimicrobial activity of iso-alpha acids, alpha acids, and beta acids, as well as their effectiveness The more non-polar a molecule is, the greater is its antimicrobial effectiveness. The bitter substances destroy the pH gradient on the cell membranes of gram-positive bacteria, which prevents the bacteria from absorbing nutrients and causes them to die. Iso-alpha acids inhibit inflammatory processes and have positive effects on fat and sugar metabolisms. In beer, they even protect against Helicobacter pylori, a type of bacterium that can trigger stomach cancer. Beta acids are effective against the growth of gram-positive bacteria such as listeria and clostridia; and they can inhibit the tuberculosis-causing pathogen Mycobacterium tuberculosis. Because of these properties, hop bitter substances can be used as natural biocides wherever bacteria must be kept in check. In the sugar and ethanol industries, beta acids have already become a successful substitute for formalin. Other possible uses of the antimicrobial properties of hops are as preservatives in the food industry (fish, meat, and dairy products) or as antibiotics in animal nutrition, as well as for sanitizing biohazardous waste (sewage sludge, compost) and for the elimination of mold infestations. They can also be used as odor and hygiene improvements in litter and for the control of allergens. It is certainly conceivable that the use of hops in these applications will increase in the future. Therefore, developing hops with an increase in beta acids is also a breeding objective in Hüll. The current record in beta-acid is at about 20%. There is even a breeding line that produces only beta and no alpha acids. This variety is used for tea.
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