Effect of spent hop extract on haze stability, total polyphenols and antioxidant activity of Pale Ale beer

Nymisha Sowgandika Ravindranath

doi:10.17918/q3e7-df63

Chilled haze formation resulting from protein-polyphenol interaction in beer is a serious problem in the brewing industry limiting consumer acceptability and storage life of the product. Commercial polyphenols such as tannic acid are often used as fining agents to clarify and stabilize beer haze. Spent hops, discarded as waste in landfills, contain some significant amounts of polyphenols and spent hop extract has potential as a fining agent. The goal of this study was to recover polyphenol rich extract from spent hops and study the influence of spent hop extract in stabilization of haze, total polyphenols and antioxidant activity of pale ale beer when added post fermentation. Total polyphenol content (TPC) contributing towards the haze formation was analyzed at each brewing stage throughout the commercial brewing of pale ale. Haze stability tests were performed on laboratory brewed pale ale. Polyphenol rich extract was recovered from spent hops using ethanol (80%). TPC and antioxidant activity(AOA) were measured using Folin Ciocelteu method and 1,1Diphenyl 2, picrylhydrazyl (DPPH), respectively. Results from this study demonstrated that TPC and antioxidant activity values in the pale ale brewing process vary with the brewing stage, significantly higher values at the end of boiling and significantly lower in the last wort. The spent hop extract has high DPPH clearance ratio (~53%), showing potential to scavenge free radicals. Addition of spent hop extract (0.3-0.5% v/v) in the beer post fermentation led to reduction in chilled haze in beer brewed with hopback wort, indicated by the decrease in NTU, TPC, and DPPH. In beer brewed from non-hopback wort, addition of spent hop extract (0.3% v/v) showed the potential to reduce NTU, TPC, and DPPH clearance ratio values during initial chilling. Extracts did not have any impact on the permanent haze after accelerated aging. Furthermore, addition of 0.2% of spent hop extract showed high TPC and DPPH clearance ratio of beer with no significant increase in turbidity values. In conclusion, addition of spent hop extracts in pale ale will reduce chilled haze formation and have no negative effect on haze stability during beer's storage life. HPLC analysis revealed the presence of haze active procyanidin B2, epicatechin and sinapic acid that are potential antioxidants found in fruits and vegetables. These polyphenols play an important role in forming protein-polyphenol complexes. Considering drawbacks of current fining agents and residual bitterness of spent hops preventing them from use in animal feed, extracting polyphenols from a plethora of natural hop waste in beer industry is a sustainable, cost effective, and effective approach to reduce waste, produce natural fining agents and increase antioxidant activity of beer product.

Effect of spent hop extract on haze stability, total polyphenols and antioxidant activity of Pale Ale beer

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Effect of spent hop extract on haze stability, total polyphenols and antioxidant activity of Pale Ale beer

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