Influence of Sample Storage on the Composition of Carbonated Beverages by MIR Spectroscopy

Abstract

It is not uncommon for research and quality control samples, including carbonated beverage samples, to be refrigerated or frozen during peak periods of production and/or sampling, when analytical demand exceeds instrumental capacity. However, the effect of sub-ambient temperatures on carbonated beverage composition during storage has not been well characterized. Mid-infrared (MIR) spectroscopy combined with principal component analysis (PCA) and traditional chemical analyses were used to evaluate the effects of refrigeration (for 1 week) and freezing (for 1 or 6 weeks) on the composition of carbonated beverages, including sparkling water, sparkling wine, beer, and cider. Carbonated beverages were generally resistant to changes in pH, titratable acidity, alcohol, total phenolics, sugar, and color, during short-term (1 week) storage. However, long-term (6 week) freezing resulted in decreased total phenolics, with acidity also affected, albeit to a lesser extent. MIR spectroscopy combined with PCA enabled discrimination of carbonated beverages based on composition, with alcohol content having a significant influence. Examination of the MIR 'fingerprint' region indicated subtle compositional changes occurred in carbonated beverages following prolonged freezing.Several studies have considered the quality of beer [2], wine [3,4], and soft drinks [5] stored at ambient or slightly elevated temperatures, in the context of shelf life. Additionally, the effects of refrigeration on wine [3] and beer [6] composition have previously been examined, by gas chromatography-mass spectroscopy (GC-MS) or ultra-performance liquid chromatography-mass spectrometry (UPLC-MS); albeit these methods are expensive, time consuming, and typically require trained staff to interpret the data. However, there is a lack of information concerning the effect of freezing on carbonated beverage composition, particularly using cost effective methods of analysis.Infrared (IR) spectroscopy is a rapid analytical technique that exploits the absorbance of light by different molecules, depending on their structural characteristics [7], which can then be used to identify components within a given matrix. Spectroscopic techniques in the mid-infrared (MIR) region have enabled characterization of many beverage constituents, including acids (malic, tartaric, and acetic acids), sugars, and alcohol [8]; with the minimal sample preparation requirements facilitating high sample throughput [9], compared to conventional GC-MS or UPLC-MS [6].Wine, beer, and cider are highly complex substrates, comprising an array of constituents at different concentrations, many at trace levels. A number of studies have been undertaken to investigate the applications of MIR spectroscopy as non-destructive, cost-effective methods of beverage analysis. In wine, MIR analysis has been used for authentication [10] and varietal identification [11], as well as for determinations of alcohol, volatile acidity, titratable acidity, pH, sulphur dioxide, sugars, esters, and/or phenolic compounds, in ...

Hydrothermal Carbonization of Brewery’s Spent Grains for the Production of Solid Biofuels

“…Storage in the fridge was thus avoided. Since it is known to have some influence on the composition of beer itself, as shown by MIR (mid-infrared) analyses performed by Pearce et al [44], immediate use was introduce as a precaution, to avoid any potential bias related to the storage of the spent grain.…”

Discrimination of Juice Press Fractions for Sparkling Base Wines by a UV-Vis Spectral Phenolic Fingerprint and Chemometrics

“…However, it is not well recognized as a technique to discriminate grape juice quality during pressing. Spectral fingerprints are the sum of instrumental signals for each significant compound present in the sample matrix and are normally acquired using detectors that generate high dimensional data (many variables per sample), such as infrared (IR), near-infrared (NIR), mid-infrared (MIR), mass (MS) and nuclear magnetic resonance (NMR) spectrometry [20][21][22][23][24]. The use of a spectrophotometric technique for discriminating juice press fractions could be of particular interest to the wine industry, since most laboratories are equipped with a UV-Vis spectrophotometer for other routine analyses.…”