Vitamins in brewing: the impact of wort production on the thiamine and riboflavin vitamer content of boiled sweet wort

Wort production contains a number of processing steps that are aimed at the optimal extraction of nutrients from malt, including vitamins. This research revealed that the different wort production processing steps imposed different influences on the thiamine and riboflavin vitamer content of the final sweet wort. These vitamins play vital roles within yeast metabolism, where they act as enzyme cofactors. As such thiamine vitamers play a crucial role in many decarboxylating enzymes, while riboflavin vitamers play an integral role in energy production and redox maintenance. While mashing releases valuable starch into the liquor, both thiamine and riboflavin are also extracted. The extraction of these vitamins is the greatest at 65°C and is indirectly linked to the amylase activity. When the starches are broken down during mashing, the thiamine and riboflavin vitamers are gradually released into the mash liquor. The boiling and trub removal (whirlpool) processes impose losses in both vitamins owing to the high temperatures exhibited during these stages. While hop pellets were shown to contribute a small proportion of the vitamers studied, the use of kettle finings caused a significant reduction in both thiamine and riboflavin vitamers. Copyright © 2014 The Institute of Brewing & Distilling     

Determination of the Boltzmann constant using a quasi-spherical acoustic resonator

The paper reports a new experiment to determine the value of the Boltzmann constant, k(B)=1.3806477(17)×10(-23) J K(-1), with a relative standard uncertainty of 1.2 parts in 10(6). k(B) was deduced from measurements of the velocity of sound in argon, inside a closed quasi-spherical cavity at a temperature of the triple point of water. The shape of the cavity was achieved using an extremely accurate diamond turning process. The traceability of temperature measurements was ensured at the highest level of accuracy. The volume of the resonator was calculated from measurements of the resonance frequencies of microwave modes. The molar mass of the gas was determined by chemical and isotopic composition measurements with a mass spectrometer. Within combined uncertainties, our new value of k(B) is consistent with the 2006 Committee on Data for Science and Technology (CODATA) value: (k(B)(new)/k(B_CODATA)-1)=-1.96×10(-6), where the relative uncertainties are u(r)(k(B)(new))=1.2×10(-6) and u(r)(k(B_CODATA))=1.7×10(-6). The new relative uncertainty approaches the target value of 1×10(-6) set by the Consultative Committee on Thermometry as a precondition for redefining the unit of the thermodynamic temperature, the kelvin.     

Shelf-life Assessment of Food Undergoing Oxidation–A Review

Oxidation is the most common event leading to the end of shelf life of microbiologically stable foods. Thus, a reliable shelf-life assessment is crucial to verify how long the product will last before it becomes oxidized to an unacceptable level to the consumers.

Shelf-life assessment strategies of foods and beverages suffering oxidation are critically discussed focusing on definition of the acceptability limit, as well as the choice of the proper oxidative indicators, and methodologies for shelf-life testing. Testing methodologies for shelf-life determination under actual and accelerated storage conditions are considered, highlighting possible uncertainties, pitfalls, and future research needs.     

What kind of intervention has the best results to reduce the weight in overweighted or obese adults?

Evidence has shown that interventions which involve changes in a person's lifestyle, such as diet and physical activity, lead to weight loss and thus reduce the risk factors of cardiovascular disease. However, the effectiveness and necessary duration of specific interventions are unclear. The purpose of this research was to evaluate and compare the effect on weight of interventions based on diet, exercise and a combination of both. The research subjects were overweight and obese adults, at six and twelve months after the beginning of the intervention. First a systematic review was carried out, followed by a meta-analysis. Initially, 24 studies were selected which met the established criteria for inclusion; twelve of these demonstrated the required level of quality. The diet-based interventions resulted in reductions of-6.66 kilograms (95% confidence interval (CI): -9.04 to -4.28) and -3.80 kilograms (CI: -5.50 to -2.10) at six and twelve months, respectively. Those who engaged in exercise showed a loss of -2.21 kilograms (CI: -4.62 to -0.21) and -2.00 kilograms (CI: -5.70 to -1.70) at six and twelve months, respectively, while those who changed their diets and engaged in exercise showed a loss of -10.86 kilograms (CI: -13.22 to -8.49) and -6.50 kilograms (CI: -8.09 to -4.90) at six and twelve months. The combination of diet and exercise showed the best effect in reducing weight among overweight and obese people, followed by diet alone while exercise alone didn't reach significant results. The effect of these interventions was greater during the first six months of intervention.     

Reducing the Gas Pressure Drop in Suction Mufflers of Hermetic Reciprocating Compressors

The suction muffler of hermetic reciprocating compressors is installed in order to attenuate the noise generated by the gas pulsation of the flow through the suction valve. However, the installation of the suction muffler affects the operation of the compressor owing to gas pressure drop, which causes volumetric and energetic efficiency loss due to the gas specific volume augmentation. Therefore, there is a compromise between sound attenuation and pressure drop increase, which has to be taken into account by compressor designers. In this work, it presents a numerical solution to the flow through a suction muffler in order to analyze the pressure field and point out the main contributions to the overall pressure drop of the flow. A commercial CFD （computational fluid dynamics） code was used to perform the numerical simulations and the results were validated by using experimental data. After analyzing the pressure field, the geometry of the muffler was modified intending to decrease the flow pressure drop. The geometric modification produced a 28% reduction on the overall pressure drop, without influencing the sound attenuation.     

Analysis of furan in coffee of different provenance by head-space solid phase microextraction gas chromatography–mass spectrometry: effect of brewing procedures

A simple, sensitive and accurate method for the analysis of furan in roasted coffee has been used based on headspace–solid-phase micro-extraction (HS–SPME) coupled to gas chromatography–mass spectrometry (GC–MS). The extraction was performed using 75-µm carboxen/polydimethylsiloxane fiber. Ionic strength, extraction time and temperature, and desorption time were assessed as the most important parameters affecting the HS–SPME procedure and d ₄-furan was used as the internal standard. The linearity range was in the range 0.0075–0.486 ng g^?1; the LOD and LOQ calculated using the signal-to-noise ratio approach were 0.002 and 0.006 ng g^?1, respectively. The inter- and intra-day precision was 8 and 10%, respectively. The concentration of furan found in batches of roasted coffee powder different producing countries ranged from 57.3 to 587.3 ng g^?1. The mean reduction in furan levels observed when brewing coffee by either infusion, using a moka pot or an expresso machine was 57, 67.5 and 63.3%, respectively.