Search: 4-vinyl guaiacol

The aromatic alcohols in beer are isolated using solid-phase extraction and are detected using gas chromatography-mass spectrometry.

4-Vinylguaiacol and 4-vinylphenol are separated by isocratic HPLC on a Spherisorb separation column and the concentration is determined by UV detection at 260 nm.

Enzymatic detection of guaiacol-forming alicyclobacilli using the peroxidase test.

In the beverage and food industries, sensory analysis is an essential part of a quality control program; for example, it serves as a valuable tool in determining the flavor stability of a beverage, in detecting any aberrations in quality, in promptly discovering fluctuations in a beverage or even in measuring the quality and intensity of certain flavor and aroma impressions. These aspects of sensory analysis represent points whereupon testing performed using laboratory equipment produces either inadequate results or fails to provide results at all. Sensory evaluation of products also affords a rapid, sensitive and specific means of assessing them. Many aroma compounds can be more readily detected with the human odor receptor cells, for the simple reason that these cells are more sensitive to such compounds than physico-chemical detectors. Results obtained from the chemical or biological analysis of finished products generally first become significant when they are consistent with results from sensory evaluation.

Therefore, before foods are introduced on the market, they should undergo sensory testing. As part of this testing, the internal and external features of the food are evaluated with the assistance of human sense organs regarding their character (e.g., sweetness) and expression (intensity as a function of time). Visual, olfactory (odor), gustatory (taste), tactile (e.g., tingling), trigeminal (e.g., burning, stabbing), kinesthetic (e.g., crispy, chewy), auditory (acoustic) impressions in addition to temperature (temperature sense) and nociception (pain perception, sensation) are differentiated.

In the case of beer, beer-based beverages, soft drinks and mineral water, the assessment is typically restricted to olfactory, gustatory, tactile and trigeminal characteristics, because other analysis methods, for example, for determining the foam stability of beer, are more accurate than a visual assessment.

Sensory analysis of food differs significantly from organoleptic evaluations for determining a person’s perceived sensitivity to certain odors and flavors. Organoleptic testing is considered a subjective sensory assessment, the results of which cannot be verified statistically. With sensory analysis, by contrast, precise procedures are employed in evaluating foods, and results are statistically assessed. The test methods in sensory analysis are standardized at an international level and include, for example, techniques for calibrating devices, which measure the physico-chemical attributes of foods, in order to obtain accurate results. Likewise, a sensory panel must be subject to certification, training and constant testing, with the ultimate goal of providing objective, accurate and reproducible results. These, in turn, allow conclusions to be made regarding the technology, raw materials and storage conditions. However, sensory analysis in the beverage industry is not only pertinent for the final product but also extends to the raw materials (e.g. brewing water, malt, hops, carbon dioxide), intermediate products (e.g. seasoning, natural lactic acid, green beer), processing aids and operating supplies (e.g., filter aids, stabilizing agents, air), auxiliary equipment and associated paraphernalia (e.g., closures, containers). Sensory analysis should comprise roughly one-third of the total analytical testing in a quality assurance program.

A distinction exists between simple sensory tests, which are part of the periodic monitoring in routine analysis of production processes, and up or down judgments, which must be reached in making ad hoc decisions. The latter are most often made by the person responsible for a particular production area, because a verdict is required quickly. Analysis of the finished product, however, must be performed by a sensory panel, because the opinion of one individual – regardless of their position – has little value. Due to ordinary inconsistencies in a person’s health, psychological condition and perception over the course of a day, a single individual is not capable of performing this function. For this reason, results from tastings by one person are always questionable and of no value for reliable quality control. The larger the number of participants on the sensory panel, the less influence the aforementioned sources of error have on the mean. Because differences also exist in the perceptive abilities of individuals, this requires that a sufficient number participate in the sensory analysis. Only an overall evaluation of the sensory panel’s results, especially if they can be expressed in a statistical form, can be considered reliable or plausible. Methods for conducting sensory analysis should therefore be selected only if they permit a statistical assessment of the results.
 

Xanthohumol and isoxanthohumol are dissolved with acetonitrile from the sample and following separation, are determined using a Nucleodur C18 column and UV detection.

Inductively coupled plasma optical emission spectroscopy (ICP-OES) is a fast and reliable method for the laboratory analysis of metals. Inductively coupled plasma (ICP), a high frequency field of ionized gas, serves as a medium for atomizing and exciting the substances found in samples. Liquid, dissolved or aerosol samples are injected into the ionized gas stream. In emission spectroscopy, ICP can be used in conjunction with a number of optical and electronic systems either simultaneously or sequentially in multi-element spectrometers. In the plasma, the atoms and ions are excited to a higher energy state bringing about the emission of electromagnetic radiation (light), primarily in the ultraviolet and visible region of the spectrum. Metals ordinarily occur as ions in the temperature range typical for ICP of 6000 to 10000 K; however, non-metals and metalloids are only partially ionized.

ICP-OES operates within a very wide range. This usually encompasses six orders of magnitude in concentrations smaller than μg/l up to g/l, depending upon the element and the concentrations used for the set of analysis data. With ICP-OES, beer and wort can also be analyzed without prior processing of the samples, in contrast to AAS. Methods for determining the following in beer and wort will be described below: Al, B, Ba, Ca, Co, Cu, Fe, K, Mg, Mn, Mo, Na, P, Si, Sr, Sn and Zn.