Process for preparing high-purity xanthohumol-containing powder and use thereof

Abstract

In a process for preparing a xanthohumol-enriched hop extract, a concentrate having contents of up to 90% xanthohumol is obtained from a xanthohumol-containing hop raw material by dissolving the xanthohumol in lye and subsequent precipitation with acid.

Description

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiment 1 (Laboratory Scale)

A markedly dark green powder having a xanthohumol content of 24.3% by weight was used for the test. 50 g of powder were suspended with 80 ml ethanol (the powder is “steeped” and is thus distributed, in the following process step, more easily and more uniformly in the alkaline solution). The suspended powder was stirred into 400 ml 0.1 N NaOH solution. The suspension was filtered out as quickly as possible.

A dark green filter cake and a yellow filtrate were obtained. The yellow filtrate was neutralised with 0.1 N HCl solution and adjusted to pH 6 for improved flocculation of the xanthohumol. The solid had to be filtered out again as quickly as possible. The filter cake obtained was washed out with water to remove the salts produced during neutralisation. The yellow/brown filter cake was then dried at 50° C. The dried filter cake had a xanthohumol content of 83% by weight. Of the xanthohumol in the green powder, 75% (relative) was recovered in the end product.

Embodiment 2 (Small-Scale Production)

The experimental plant consisted of

• • two pumps,
  • a respective container for receiving the suspension of xanthohumol in ethanol or a suspension of diatomite (filtering auxiliary means) in 0.1 N sodium hydroxide solution,
  • a mixing section where the xanthohumol suspension was injected into the lye,
  • a mixer,
  • a precoat filter,
  • a receiving tank filled with 0.1 N hydrochloric acid and
  • a further filter (consisting of a Buchner funnel in the test).

Before the start of the addition, coarse, then fine diatomite was first pumped onto the precoat filter. In the test, 20 l of lye and 1.4 kg diatomite were used per kg of green powder.

1 kg of the markedly dark green powder was suspended in 1.6 l ethyl alcohol. This suspension was injected through a nozzle into a tube through which a further suspension of lye and diatomite was pumped. Xanthohumol was dissolved, other components such as, for example, chlorophyll remained undissolved. Immediately after the mixing zone there was installed a high-speed stirrer causing highly effective distribution. This mixture was pumped onto a precoat filter (lye and diatomite). Compressed air was applied to the filter container to accelerate filtration. The filtering process was repeated several times (pressure reduction, refilling, pressure build-up to filtering) until the suspension prepared had been filtered. The solution was neutralised immediately, whereupon there precipitated yellow xanthohumol. This solution was also filtered. The remaining xanthohumol was washed with water and then dried in a drying oven.

The xanthohumol content of the dried filter cake was between 75 and 85% by weight. Of the xanthohumol in the green powder, 72% (relative) was recovered in the end product. The increase in yield was a further aim, although this was said to be achieved using the conventional methods.

GENERAL CONCLUSIONS

The suspension of the xanthohumol powder causes dissolution of resinous components and facilitates the formation of a uniform suspension. The type of solvent used is not important. The solvent must merely be non-toxic, on account of the risk of non-admitted residues, and must dissolve in water.

The residence time of the xanthohumol powder in the lye should be as short as possible, otherwise isoxanthohumol, which may be undesirable, forms. The residence time of the xanthohumol powder in the acid should also be as short as possible, otherwise derivatives and decomposition products of xanthohumol form.

Claims

1. A process for preparing a high-purity (60-90%) xanthohumol-containing powder from hops including the following process steps: preparing a xanthohumol-enriched hop extract by extracting a xanthohumol-containing hop raw material using highly compressed CO2 as a solvent at pressures above 500 bar and at temperatures above 60° C.,suspending the xanthohumol-enriched hop extract in an alkaline solution for separation between by-products and xanthohumol, the xanthohumol preferentially being dissolved,separating the undissolved by-products,neutralisating and precipitating the dissolved xanthohumol with acid,separating the precipitated xanthohumol concentrate from the acid, anddrying the separated concentrate.

2. A process according to claim 1, wherein before the xanthohumol-enriched hop extract is suspended in the alkaline solution, it is suspended in a solvent.

3. A process according to claim 2, wherein the solvent consists of an alcohol of low molecular weight.

4. A process according to claim 3, wherein the solvent is ethanol.

5. A process according to claim 1, wherein the alkaline solution for suspension is sodium hydroxide solution.

6. A process according to claim 1, wherein the acid is hydrochloric acid.

7. A process according to claim 1, wherein the dissolved xanthohumol is separated from the undissolved by-products in a precoat filter.

8. A process according to claim 7, wherein diatomite is used as a filter auxiliary means.

9. A process according to claim 1, wherein the xanthohumol reprecipitated by the addition of acid is separated from the still dissolved constituents by filtration.

10. A process according to claim 1, wherein the dried xanthohumol concentrate is crushed.

11. Use of a high-purity xanthohumol-containing powder prepared in accordance with any one of the preceding claims, wherein the hop extract is used as an admixture to solid, paste-like or liquid foods.