Beer astringency assessed by time–intensity and quantitative descriptive analysis: Influence of pH and accelerated aging

Unveiling the applications of membrane proteins from oil bodies: leading the way in artificial oil body technology and other biotechnological advancements

Oil bodies (OBs) function as organelles that store lipids in plant seeds. An oil body (OB) is encased by a membrane composed of proteins (e.g., oleosins, caleosins, and steroleosins) and a phospholipid monolayer. The distinctive protein-phospholipid membrane architecture of OBs imparts exceptional stability even in extreme environments, thereby sparking increasing interest in their structure and properties. However, a comprehensive understanding of the structure-activity relationships determining the stability and properties of oil bodies requires a more profound exploration of the associated membrane proteins, an aspect that remains relatively unexplored. In this review, we aim to summarize and discuss the structural attributes, biological functions, and properties of OB membrane proteins. From a commercial perspective, an in-depth understanding of the structural and functional properties of OBs is important for the expansion of their applications by producing artificial oil bodies (AOB). Besides exploring their structural intricacies, we describe various methods that are used for purifying and isolating OB membrane proteins. These insights may provide a foundational framework for the practical utilization of OB membrane proteins in diverse applications within the realm of AOB technology, including biological and probiotic delivery, protein purification, enzyme immobilization, astringency detection, and antibody production.

FAPD: An Astringency Threshold and Astringency Type Prediction Database for Flavonoid Compounds Based on Machine Learning

Astringency is a puckering or velvety sensation mainly derived from flavonoid compounds in food. The traditional experimental approach for astringent compound discovery was labor-intensive and cost-consuming, while machine learning (ML) can greatly accelerate this procedure. Herein, we propose the Flavonoid Astringency Prediction Database (FAPD) based on ML. First, the Molecular Fingerprint Similarities (MFSs) and thresholds of flavonoid compounds were hierarchically clustering analyzed. For the astringency threshold prediction, four regressions models (i.e., Gaussian Process Regression (GPR), Support Vector Regression (SVR), Random Forest (RF), and Gradient Boosted Decision Tree (GBDT)) were established, and the best model was RF which was interpreted by the SHapley Additive exPlanations (SHAP) approach. For the astringency type prediction, six classification models (i.e., RF, GBDT, Gaussian Naive Bayes (GNB), Support Vector Machine (SVM), k-Nearest Neighbor (kNN), and Stochastic Gradient Descent (SGD)) were established, and the best model was SGD. Furthermore, over 1200 natural flavonoid compounds were discovered and built into the customized FAPD. In FAPD, the astringency thresholds were achieved by RF; the astringency types were distinguished by SGD, and the real and predicted astringency types were verified by t-Distributed Stochastic Neighbor Embedding (t-SNE). Therefore, ML models can be used to predict the astringency threshold and astringency type of flavonoid compounds, which provides a new paradigm to research the molecular structure-flavor property relationship of food components.

Sensory Profile of Kombucha Brewed with New Zealand Ingredients by Focus Group and Word Clouds

Kombucha is a yeast and bacterially fermented tea that is often described as having an acetic, fruity and sour flavour. There is a particular lack of sensory research around the use of Kombucha with additional ingredients such as those from the pepper family, or with hops. The goal of this project was to obtain a sensory profile of Kombucha beverages with a range of different ingredients, particularly of a novel Kombucha made with only Kawakawa (Piper excelsum) leaves. Other samples included hops and black pepper. Instrumental data were collected for all the Kombucha samples, and a sensory focus group of eight semi-trained panellists were set up to create a sensory profile of four products. Commercially available Kombucha, along with reference training samples were used to train the panel. Kawakawa Kombucha was found to be the sourest of the four samples and was described as having the bitterest aftertaste. The instrumental results showed that the Kawakawa Kombucha had the highest titratable acidity (1.55 vs. 1.21–1.42 mL) as well as the highest alcohol percentage (0.40 vs. 0.15–0.30%). The hops sample had the highest pH (3.72 vs. 3.49–3.54), with the lowest titratable acidity (1.21), and, from a basic poll, was the most liked of the samples. Each Kombucha had its own unique set of sensory descriptors with particular emphasis on the Kawakawa product, having unique mouthfeel descriptors as a result of some of the compounds found in Kawakawa. This research has led to a few areas that could be further studied, such as the characteristics of the Piperaceae family under fermentation and the different effects or the foaminess of the Kawakawa Kombucha, which is not fully explained.

Panel and Panelist Performance in the Sensory Evaluation of Black Ripe Olives from Spanish Manzanilla and Hojiblanca Cultivars

There is vast experience in the application of sensory analysis to green Spanish-style olives, but ripe black olives (≈1 × 10⁶ kg for 2016/2017) have received scarce attention and panelists have less experience on the evaluation of this presentation. Therefore, the study of their performance during the assessment of this presentation is critical. Using previously developed lexicon, ripe olives from Manzanilla and Hojiblanca cultivars from different origins were sensory analysed according to the Quantitative Descriptive Analysis (QDA). The panel (eight men and six women) was trained, and the QDA tests were performed following similar recommendations than for green olives. The data were examined while using SensoMineR v.1.07, programmed in R, which provides a diversity of easy to interpret graphical outputs. The repeatability and reproducibility of panel and panelists were good for product characterisation. However, the panel performance investigation was essential in detecting details of panel work (detection of panelists with low discriminant power, those that have interpreted the scale in a different way than the whole panel, the identification of panelists who required training in several/specific descriptors, or those with low discriminant power). Besides, the study identified the descriptors of hard evaluation (skin green, vinegar, bitterness, or natural fruity/floral).

Multiple-sip temporal dominance of sensations associated with acceptance test: a study on special beers

In this study, we proposed the use of a multiple-sip temporal dominance of sensations (TDS) test alongside with an acceptance test over repeated consumption for the analysis of special beers, with the aim of contributing to a deeper understanding of consumer behavior regarding temporal descriptions and sensory acceptance. Consumers of special beers sequentially evaluated six sips of a particular type of beer by TDS analysis and an acceptance test was performed for each sip. Four different kinds of specialty beers were evaluated [Bohemian Pilsner (BP), Witbier (WB), Belgian Strong Ale Dubbel (BD), and Russian Imperial Stout (RS)]. In general, the descriptive profile of beers varied temporally, i.e., there was an increased dominance of bitterness and a decreased dominance of fruity, floral, toffee, and coffee attributes. Concurrently, a reduction in sensory acceptance with an increased number of sips, especially the last sip, was observed in two kinds of beers that possessed a strong flavor, BD and RS. BP and WB presented smooth attributes and low notable characteristics, which could have contributed to the maintenance of the acceptance grades as the number of sips increased. The combination of TDS and acceptance over repeated sips can be useful for obtaining detailed descriptions of products that are closer to real time consumption by consumers, and thus aids in ensuring good product performance once released. The information obtained can also help product development scientists to fine-tune product formulations and ensure acceptability.

Exploring the flavor life cycle of beers with varying alcohol content

Decreasing alcohol in beer and increasing the pleasure of lower alcohol beers is a potential way to limit total alcohol consumption. Consumers’ willingness to drink alcohol‐reduced beers is mainly limited by unfavorable flavor characteristics that arise during consumption. To investigate the temporal flavor dominance during consumption, we analyzed the five most dominant beer flavors from nine different beers among three types of beer with varying alcohol content to assess the Flavor Life Cycle. Results show that beers with different alcohol content displayed similar flavor dominance (e.g., bitterness) and displayed differences in worty‐off flavor, malty flavor, and astringency. In alcohol‐free beers, worty‐off flavor was most pronounced in dominating between 5 and 30 s and malty flavor increased after swallowing. For bitterness and astringency, higher alcohol content resulted in higher flavor dominance, especially prior to swallowing (≤40 sec). Based on these findings, we provide some brief advice to minimize unfavorable flavor experience during consumption of beer with lower alcohol. For now, consumers who want to enjoy beers with lower alcohol should consider flavor changes and focus on the favored and defocus on the less favored flavors.

Prediction of the ageing of commercial lager beer during storage based on the degradation of iso-α-acids

BACKGROUND

Iso-α-acids and their chemically modified variants are responsible for the bitterness of beer and play a disproportionately large role in the final quality of beer. The current study was undertaken to predict the degradation of commercial lager beers related to changes in the concentration of trans-iso-α-acids during storage by using high-pressure liquid chromatography.

RESULTS

In the analysed beers the concentration of isohumulone (average concentration 28 mg L(-1)) was greater than that of isocohumulone (20 mg L(-1)) and isoadhumulone (10 mg L(-1)). The kinetic parameters, activation energy and rate constant, of the trans-iso-α-acids were calculated. In the case of dark beers, the activation energy for the degradation of trans-isocohumulones was found to be higher than for trans-isohumulones and trans-isoadhumulones, whereas in pale and alcohol-free beers activation energies for the degradation of the three trans isomers were similar.

CONCLUSION

The loss of iso-α-acids can be calculated using the activation energy of the degradation of trans-iso-α-acids and the temperature profile of the accelerated ageing. The results obtained in the investigation can be used in the beer industry to predict the alteration of the bitterness of beer during storage.

Probing beer aging chemistry by nuclear magnetic resonance and multivariate analysis

This paper describes the use of nuclear magnetic resonance (NMR) spectroscopy, in tandem with multivariate analysis (MVA), for monitoring the chemical changes occurring in a lager beer exposed to forced aging (at 45°C for up to 18 days). To evaluate the resulting compositional variations, both principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) were applied to the NMR spectra of beer recorded as a function of aging and a clear aging trend was observed. Inspection of PLS-DA loadings and peak integration enabled the changing compounds to be identified, revealing the importance of well known markers such as 5-hydroxymethylfurfural (5-HMF) as well as a range of other relevant compounds: amino acids, higher alcohols, organic acids, dextrins and some still unassigned spin systems. In addition, the multivariate analysis method of 2D correlation analysis was applied to the NMR data enabling the relevant compound variations to be confirmed and inter-compound correlations to be assessed, some reflecting common metabolic/chemical pathways and, therefore, offering improved insight into the chemical aspects of beer aging.