Beer consumers are accustomed to a product that offers a pleasant and well-defined taste. However, in alcohol-free and alcohol-reduced beers these characteristics are totally different from those in regular beer. Therefore, it is important to evaluate and determine the different flavor compounds that affect organoleptic characteristics to obtain a product that does not contain off-flavors, or taste of grass or wort. The taste defects in alcohol-free beer are mainly attributed to loss of aromatic esters, insufficient aldehydes, reduction or loss of different alcohols, and an indeterminate change in any of its compounds during the dealcoholization process. The dealcoholization processes that are commonly used to reduce the alcohol content in beer are shown, as well as the negative consequences of these processes to beer flavor. Possible strategies to circumvent such negative consequences are suggested.

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As the beer market is steadily expanding, it is important for the brewing industry to offer consumers a product with the best organoleptic characteristics, flavour being one of the key characteristics of beer. New trends in instrumental methods of beer flavour analysis are described. In addition to successfully applied methods in beer analysis such as chromatography, spectroscopy, nuclear magnetic resonance, mass spectrometry or electronic nose and tongue techniques, among others, sample extraction and preparation such as derivatization or microextraction methods are also reviewed.

AimsTo report new information related to acute retinal toxicity of Bio Octane Plus, a mixture of 90% perfluorooctane (PFO) and 10% perfluorohexyloctane.MethodsThis retrospective, descriptive case series reports the occurrence of acute retinal toxicity after vitreoretinal surgery in which Bio Octane Plus (batch number 1605148) was used as an endotamponade. Cytotoxicity biocompatibility tests and chemical analyses by Fourier-transformed infrared (FTIR) spectroscopy and gas chromatography-mass spectrometry (GC-MS) of the presumed toxic product were performed.ResultsFour patients presented with acute severe visual loss after uneventful ocular surgery assisted by Bio Octane Plus (batch number 1605148) as endotamponade. Patients experienced extensive retinal vascular occlusion leading to retinal and optic nerve atrophy. The viability of ARPE-19 cells directly exposed to the suspect batch for 30 min was 0%. The agarose overlay method used by the manufacturer according to European Union regulations and International Organization for Standardization (ISO) International Standards failed to detect toxicity. FTIR spectroscopy showed small differences between the non-toxic and toxic batches. GC-MS analysis showed the presence of bromotributyl stannane (whose toxicity was demonstrated in the dose–response curve) only in the toxic batch of Bio Octane Plus.ConclusionThis is the third report of retinotoxicity due to PFO in 4 years. The clinical profiles may be missed as they resemble other postsurgical complications; therefore, more cases worldwide could have gone unreported. Protocols to determine cytotoxicity of intraocular medical devices and approved by the ISO International Standards based on indirect methods have failed and should be revised to ensure safety.

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Alcohol-free beers are characterized by less aroma and body than regular ones. Seven flavor compounds were chosen as indicators in dealcoholization experiments at 102 and 200 mbar. Compounds were analyzed by headspace (HS)-solid phase microextracion (SPME)-gas chromatography-mass spectrometry (GC-MS). Also, contents of aroma-related compounds were compared between commercial regular and alcohol-free beers. In dealcoholization experiments by vacuum distillation, most of the compounds were shown to be evaporated in the first vapor fraction. The compounds that mainly remained in alcohol-free beers were amyl alcohols and 2-phenylethanol; this might explain their characteristic sweet and, to a lesser extent, fruity and flowery flavors. Regular beers were mainly characterized by 1-butanol, amyl alcohols, and ethyl acetate. Beers dealcoholized at 102 mbar are characterized by a high concentration of 2-phenylethanol. Beers dealcoholized at 200 mbar and commercial non-alcoholic beers had a similar flavor profile, which is characterized by low concentrations of the compounds used as indicators.

The coupled operation of vacuum distillation process to produce alcohol free beer at laboratory scale and Aspen HYSYS simulation software was studied to define the chemical changes during the dealcoholization process in the aroma profiles of 2 different lager beers. At the lab-scale process, 2 different parameters were chosen to dealcoholize beer samples, 102 mbar at 50°C and 200 mbar at 67°C. Samples taken at different steps of the process were analyzed by HS-SPME-GC-MS focusing on the concentration of 7 flavor compounds, 5 alcohols and 2 esters. For simulation process, the EoS parameters of the Wilson-2 property package were adjusted to the experimental data and one more pressure was tested (60 mbar). Simulation methods represent a viable alternative to predict results of the volatile compound composition of a final dealcoholized beer.