Isabel Caballero

Free iron in pale, dark and alcohol-free commercial lager beers

BACKGROUND A highly sensitive, selective, rapid, reliable and inexpensive method has been developed for the direct analysis of free iron in 40 samples of bottled lager beer. RESULTS A differential pulse adsorptive stripping voltammetry technique at a hanging mercury drop electrode without any sample digestion was performed. The iron content in the analysed samples was in the range of 41 to 165 ppb. CONCLUSIONS The results point out that dark beers keep the highest free iron concentrations, which may be related to the highest amounts of minor ingredients in dark beers. Meanwhile, alcohol-free beers present the lowest free iron concentrations. Some discussion is presented regarding the basis of the free and complexed iron in beer and its participation as an essential element in the human diet.

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.

Innovations in the brewing industry: light beer

Abstract The demand for light beers has led brewers to innovate by developing light beer. However, these products are not widely accepted in Europe compared to North America and Australasia because of their lack of fullness in the taste and low bitterness compared with conventional beer. The lower levels of some important compounds, present in light beer, can explain these features since they are responsible for the characteristics of the beer. These include alcohol soluble proteins, oligosaccharides, glycerol, polyphenols, iso-α-acids, fusel alcohols and trihydroxy fatty acids. Light beer is produced by several methods, the most commonly used is the addition of glucoamylase to the wort before or during fermentation. This enzyme metabolizes residual carbohydrates (mainly dextrins) transforming them into fermentable sugars and reducing the caloric and alcohol content in this type of beer. Recently pilot studies have been carried out with genetically engineered yeast strains in which amylolytic genes are introduced into the yeast genome in order to metabolize carbohydrate residues. When introducing amylolytic genes, a better fermentability occurs although the fullness of flavor still becomes reduced.

Nuclear Magnetic Resonance Methodology for the Analysis of Regular and Non-Alcoholic Lager Beers

The presence of seven main agents responsible for beer aroma and taste (n-propanol, isobutanol, 3-methylbutanol, tyrosol/tyrosine, ethyl acetate, isoamyl acetate, and acetaldehyde) is determined by different nuclear magnetic resonance (NMR) techniques (1H PRESAT, total correlation spectroscopy, heteronuclear single quantum correlation, and heteronuclear multiple bond correlation) in five regular and five low-alcoholic or alcohol-free beers. The new methodology includes the identification of the 1H and 13C NMR chemical shifts of the analytes by a standard addition method and the consequent identification of the compounds studied in regular and non-alcoholic beers. The chemical composition is different depending on whether the beer is regular or non-alcoholic, therefore affecting the organoleptic characteristics of each type of beer.

Thermal Deterioration of the Trans-/Cis-Ratio of Bittering Agents of Commercial Beers

The use of reduced isomerised hop extracts to achieve both bitterness and light stability became very popular during the last decade. Changes during storage in four hop extracts and seven commercial lager beers are studied using HPLC and spectrophotometric techniques. The degradation of the iso-α-acids and tetrahydro iso-α-acids as a function of time is represented by the ratio, in percentage, of the sum of trans-isomer concentration to the sum of the cis-isomer concentration (T/C). The results provided conclusive evidence that the gradual decreased of bitterness intensity in beer was due to the degradation of iso-α-acids, notably to the instability of the trans-iso-α-acids. When the beers were stored for 14 days at 45°C the decrease of the T/C average varied from 8.6 to 14.0%, except in lemon beer, in which case, T/C decreased 36.9%. The results allowed us to infer that in open storage and/or warm conditions the deterioration of beer was critical above 35°C. On the other hand, the results showed that tetrahydro iso-α-acids remained unaltered.

Technoscience, Hermeneutic and Society Oriented to the Person

This article becomes the first step towards technoscience as an opened and inter-penetrated enabler. For this the authors develop a theoretical and hermeneutical analysis of the techno-scientific system. A brief history of the modern occidental science is presented. Later, this article offers the first approach to a trans-subjective or trans-personal theory within the Latin American context. The authors show different reactions to the so-called ‘monologated scientific system’ in relationship to the hermeneutic of the person. Later the authors show a more dialogistic system in which other epistemic views are considered. These are connected with the philosophy of wisdom, the theory of personal care, etc. In this sense, and finally, it is considered that the techno-scientific system could be inter-penetrated for the psychic and social scope. In fact, this affirmation is defended to reach a scientific personal progress in a permanent dialogue with other wisdom knowledge.