Sensory and Olfactometry Chemometrics as Valuable Tools for Assessing Hops' Aroma Impact on Dry-Hopped Beers: A Study with Wild Portuguese Genotypes

Abstract

Sensory, olfactometry (using the sums of odour intensities for each class of compounds) and chemometric analyses were used to evaluate Portuguese wild hops' sensory characteristics and the aroma that those hops impart to dry-hopped beer. CATA analysis and agglomerative hierarchical clustering was applied for the sensory characterization of 15 wild hops of Portuguese genotypes, clustering them in two groups: one more sulphurous, floral, and fruity, and another more earthy, resinous, floral, and non-citrus fruits. Two hops representative of each group were selected for the production of four dry-hopped beers using the same base beer style (Munich Helles). Beers were analysed by quantitative descriptive analyses and quantification of hop-derived key volatile compounds. Multivariate statistical treatment of the data was performed. Results indicate significant differences (p < 0.05) in fruity, resinous, earthy, floral, and sulphurous attributes of hops, but the dry-hopped beers only have a significant increase (p < 0.05) in fruity and spicy notes when compared with non-dry-hopped Munich-style Helles beer. Hop olfactometry explained the sensory perception that the 11 hops not used for brewing (employed as supplementary observations) are placed into the space of the odour-active compounds profile of the four hops selected for brewing. These 11 hop samples have more spiciness than fruitiness potential.

Keywords: CATA; aroma compounds; beer; certified assessors; multivariate statistical analysis; olfactometry; quantitative descriptive analysis; wild hops.

Figure 1

Agglomerative Hierarchical Clustering and Correspondence Analysis of Portuguese wild hops sensory attributes.

Figure 2

Quantitative descriptive sensory analysis of beers dry-hopped with Portuguese wild hops. Each beer score is represented by a different colour. PT05 (blue), PT11 (red), PT14 (yellow), PT15 (green), and non-dry-hopped beer in the grey area. Data from sensory analysis performed by trained panellists are presented as means (floral) in normal distribution or medians (other attributes) in non-normal distribution. Two independent samples t-test and Mann-Whitney test were applied to detect which attributes were significant in normal and non-normal distributions. Letters between brackets represent that (a) PT14, (b) PT11, (c) PT05, and (d) all hops presented significant statistical differences (p < 0.05) of the attribute in comparison with non-dry-hopped beer.

Figure 3

Principal Component Analysis (PCA) biplots of sensory attributes (blue circle) and volatile compounds content (black open circles) of dry-hopped beers (blue triangles) used as active variables. Liking scores (green square) were used as a passive (supplementary) variable.

Figure 4

Principal Component Analysis (PCA) biplot using as active variables the olfactometry data (red circles) of the 4 hops (blue triangles), while the sensory attributes (blue circles) and volatile compounds quantified in the dry-hopped beers (open black circles) were used as passive (supplementary) variables and olfactometry data of the other 11 hop samples (open green triangles) were included as supplementary observations.