Isotopic composition of dissolved inorganic carbon in bottled waters on the Slovene market

This study investigates the stable isotopic composition of dissolved inorganic carbon (DIC), expressed as δ¹³C_DIC, in domestic and foreign bottled waters randomly collected on the Slovene market. All together 58 brands and 16 replicates were analysed. The δ¹³C_DIC values varied between −63.1‰ and +1.0‰ with an average of −12.3‰. Average δ¹³C_DIC values for naturally sparkling, artificially sparkling, still and flavoured waters were −3.3‰, −36.5‰, −10.0‰ and −11.0‰, respectively. The lowest values are characteristic of artificial sparkling waters (minimum −63.1‰) and can be attributed to injection of industrial CO₂ during bottled water production. Therefore, determination of the isotopic composition of DIC can represent a useful analytical tool to distinguish between natural and artificially sparkling waters. Furthermore, the method used enabled determination of the various origins of still waters. From the bottled waters sampled it was possible to discern waters that originate from deeper aquifers, from aquifers in equilibrium with soil CO₂, or from aquifers with their recharge in a mountainous area. Finally, δ¹³C_DIC values of flavoured waters illustrate that isotopic fractionation occurs during the production process and that δ¹³C_DIC values in products of some producers have a large variation.     

The application of SNIF‐NMR and IRMS combined with C,H and O isotopes for detecting the geographical origin of Chinese wines

The regional origin of Chinese wines was investigated using two important complementary techniques, site‐specific natural isotopic fractionation nuclear magnetic resonance (SNIF‐NMR) and isotope ratio mass spectrometry (IRMS). Twenty samples from five different grape varieties were collected from north Xinjiang in 2009, along with 100 wine samples from five different regions during 2010–2013. The (D/H)_I and (D/H)_II in wine ethanol ranged from 95.10 to 102.86 ppm and from 115.99 to 126.39 ppm using SNIF‐NMR, respectively. The ¹³C/¹²C of wine ethanol and ¹⁸O/¹⁶O of wine water were detected using IRMS. The δ¹³C value (?23.36‰) in coastal regions was higher than that in continental regions (?27.75‰). The temperature is the key for δ¹³C value. The δ¹⁸O ranged from ?1.94 to 4.57‰. The δ¹⁸O values were only positive in north Xinjiang which had the arid climate and strong sunshine. No difference was found for isotope ratios for wines made from five different grape varieties in north Xinjiang. All data evaluated by principal component analysis and linear discriminant analysis showed that the best method to distinguish the regional wine origin correctly is a combination of (D/H)_I, (D/H)_II, R, δ¹³C and δ¹⁸O. Therefore, natural multi‐elemental isotope ratios are effective in contributing to wine quality control in the Chinese market.     

Comparison between isotope ratio mass spectrometry (IRMS) and cavity ring-down spectroscopy (CRDS) for analysing the carbon isotope ratio and detection of adulteration in coconut water

This study investigated the carbon isotope ratio (¹³C/¹²C, δ¹³C in unit of parts per thousand or per mill, ‰) of different coconut water samples using elemental analysis isotope ratio mass spectrometry (EA-IRMS) and combustion module cavity ring-down spectroscopy (CM-CRDS). Natural coconut water from young coconuts from 12 provinces in Thailand (n = 94), adulterated coconut water containing three sweeteners (sucrose, glucose and fructose) at different concentrations and eight brands of commercial coconut water were analysed. The δ¹³C of all samples were not significantly different (P > 0.05) between the EA-IRMS and CM-CRDS analyses. The natural coconut water (C3 plant) had δ¹³C ranging from −21.58‰ to −27.79‰ (mean −24.64 ± 0.91‰). Three sweeteners (C4 plant) contained δ¹³C between −11.46‰ to −13.16‰. The use of δ¹³C determination can detect adulteration of a singular extraneous sweetener (either glucose or sucrose) down to a level of 2% of adulteration. For the detected δ¹³C values of commercial products labelled as ‘no added sugar’, about 50% of products were adulterated. This study demonstrates that CM-CRDS can be used as an alternative analytical platform to EA-IRMS for detecting adulterated products, especially coconut water.     

Carbonation monitoring of beverage in a laboratory scale unit with on-line measurement of dissolved CO2

The effervescence properties of carbonated drinks are subject to the concentration of carbon dioxide dissolved and its ability to be transferred from the liquid phase to the forming bubble. We report the construction of a small laboratory scale carbonation unit that allows the study of the solubility of carbon dioxide in various hydro-alcoholic media, differing in their compositions. This unit, which is a model of a real industrial one, measures the instant concentration of CO₂, during the carbonation process, by means of a thermal conductivity detector. The carbonation kinetics of various samples, containing water, alcohol, sugar, proteins and free amino-acids, were studied. While sugar diminishes CO₂ solubility and, consequently, carbonation kinetics, free amino-acids and proteins increase the concentration of carbon dioxide in the medium. A survey of the rheological properties of the samples showed that CO₂ solubility modifications are not correlated with changes in the viscosity of the medium. This equipment could be helpful for soft drink bottlers for measuring the changes that may affect effervescence and consequently the visual and gustative perception of the beverage after modification of its composition.     

Helping to authenticate sparkling drinks with 13C/12C of CO2 by gas chromatography-isotope ratio mass spectrometry

We applied direct injections of headspace gas into a Gas Chromatography – Combustion – Isotope Ratio Mass Spectrometry (GC-C-IRMS) system to measure ¹³C/¹²C isotopic ratio of carbon dioxide from the headspace of several sparkling and soft-drinks. This straightforward technique, which consists in an automated analysis of the headspace sample with no prior purification steps, improves the determination of δ¹³C values of CO₂ gas as a food probe authenticity. However, for an ultimate test, combination with other isotopic data is required.     

Mechanism of gushing induction by carbon dioxide transfer activator

The article deals with the activation of carbon dioxide transfer from carbonated beverages. As a model compounds agents produced by Trichoderma reesei and harzianum and degraded hop iso‐extract were selected. These substances were added to the carbonated water or beer and their effect was compared. The method of pressure growth in the bottle headspace after rapid piercing and re‐closing the bottle was used. Some carbon dioxide transfer activators accelerated CO₂ escape even at rest; others required shaking for different periods. The pressure growth measurement allowed the prediction of gushing before its occurrence. Copyright © 2017 The Institute of Brewing & Distilling     

Carbon Stable Isotope Analysis for Glucose in Sake: Simple Freeze-Dried Sake Can Substitute for Glucose Following HPLC Isolation

Carbon stable isotope analysis of ethanol is an established method for determining the authenticity of alcoholic beverages, but there is no accepted method for measurements of glucose carbon stable isotopic composition (δ ¹³C). This study aims to establish two methods to determine accurately the δ ¹³C value of glucose isolated from sake by high-performance liquid chromatography (HPLC) after three clean-up steps using ion exchange chromatography and in simple freeze-dried sake (total nonvolatile matter) and to examine two methods that yield different δ ¹³C values. In the glucose isolation procedure, the δ ¹³C values of glucose were not significantly affected by the glucose concentration, solvent (water or aqueous acetonitrile), drying method (freeze-dry or nitrogen-spraying), the clean-up step using ion exchange chromatography (weakly acidic cation-exchange, strongly acidic cation-exchange, and weakly basic anion-exchange resins), or HPLC isolation. Glucose nitrogen spray-dried after isolation by ion exchange chromatography and HPLC showed a carbon isotope discrimination value of <0.1 ‰. The glucose δ ¹³C values ranged from ?26.8 to ?25.5 ‰ in authentic sake and from ?27.0 to ?11.0 ‰ in commercial sake samples. This HPLC isolation approach may provide a first step toward visualizing the brewing process via isotopic carbon flow during fermentation. Additionally, there was no significant difference between the δ ¹³C values of glucose and total nonvolatile matter from sake. The δ ¹³C measurement of simple freeze-dried sake can substitute for glucose δ ¹³C measurement using HPLC isolation, thus aiding high-throughput detection of carbon derived from C₄ plants in sake.     

Authenticity assessment of 2- and 3-methylbutanol using enantioselective and/or 13C/12C isotope ratio analysis

Enantioselective gas chromatography and/or ¹³C/¹²C isotope ratio analysis are suitable tools for the authenticity assessment of the fusel alcohols, 2- and 3-methylbutanol (1 and 2, respectively). The chiral compound, 1 is biosynthesised almost completely as the (S)-enantiomer, regardless of which carbohydrate source is used for fermentation. The type of CO₂ fixation and some plant-specific influences were of prime importance to the ¹³C/¹²C isotope ratios of the starting materials in alcoholic fermentation, and the δ¹³C values of 1 and 2 differed significantly. In general, the δ¹³C values of 2 were about 4–5ö lower than those of 1 produced via the same fermentation process. ¹³C/¹²C isotope ratio analysis results can be used to determine between fusel alcohols produced from different sources, and provides a new and valuable method of authenticity assessment.     

Comparative environmental impact analysis of techniques for cleaning wood wine barrels

We compare four techniques that are commonly used for cleaning and disinfection of oak wine barrels with 225 l of capacity used in the red wine aging process through a life cycle analysis (LCA). The analysed techniques were pressurised water (at 90 °C) plus sulphur dioxide (SO₂) wick (7.5 g per barrel), water vapour (at 105 °C) plus sulphur dioxide (SO₂), ozone (O₃) (4 ppm), and carbon dioxide (CO₂) (50 kg/h for 180 s). The results showed that the barrel cleaning technique with the lowest impact on all water scarcity indexes and is the carbon dioxide, due mainly to low water usage. However, in the global warming category, carbon dioxide technology is the technique that has the greatest environmental impact with a value of 4.080 kg CO₂ per cleaned barrel, due mainly to CO₂ and air consumption.     

Determining adulteration of canned products using SNIF-NMR and IRMS: detection of undeclared addition of synthetic acetic acid

Possible adulteration of canned products containing spirit vinegar pickle by adding synthetic acetic acid is a significant problem of the food industry. Isotope analyses, which determine botanical origin of acetic acid and also can detect synthetic acid, were applied to detect undeclared addition of synthetic acetic acid to canned products. The aim of the study was to improve the extraction technique for the SNIF-NMR (²H/¹H; site-specific natural isotopic fractionation-nuclear magnetic resonance) and IRMS (¹³C/¹²C; isotope ratio mass spectrometry) isotope methods and for an atypical matrix and to determine isotope ratios in canned vegetables pickle to prove their adulteration or authenticity. The following set of canned products was analysed: pickled cucumbers (n = 16) and one vinegar pickle purchased in the Czech market and six model (cucumber) pickles. The determined ratios of ²H/¹H and ¹³C/¹²C for the pickled cucumbers proved to be authentic ranged from 89.4 to 107.0 ppm and from ?28.7 to ?15.6 ‰, respectively; for the synthetic acetic acids diluted with water they ranged from 114.2 to 129.0 ppm and from ?44.9 to ?33.4 ‰, respectively. Isotope analyses were confirmed as a reliable tool for assessing authenticity of canned products. The method enables detection of synthetic acetic acid addition into vinegars and canned vegetables containing vinegar pickle up from 20 % (of total acidity).     

酿造食醋中碳、氧同位素比值的测定及应用研究

以酿造食醋为研究对象,建立元素分析/连续流-稳定同位素比质谱法（EA/GasBench Ⅱ-IRMS）测定食醋总碳、水中氧同位素比值（δ13C和δ18O）的方法。通过优化稀释倍数与进样体积,得到δ13C值测定最佳条件为食醋稀释2倍,进样体积1.0 μL;通过优化平衡时间和样品体积,得到δ18O值测定时平衡时间为24 h,样品体积为500 μL。结果表明,在最佳条件下,食品样品碳同位素比测定值标准偏差（SD）值均＜0.30‰,氧的同位素比测定值的SD值均＜0.10‰,表明该测定方法的稳定性较好。山西食醋总碳δ13C值分布在-23.26‰～-20.80‰,水中氧的δ18O值在-5.66‰～-4.49‰;镇江食醋总碳δ13C值在-25.93‰～-20.70‰,水中氧的δ18O值在-8.35‰～-5.61‰;结合碳氧同位素比值分析,可以将山西老陈醋、镇江香醋和镇江陈醋区分开（P＜0.01）。     

Measurement of stable isotope abundances in milk and milk ingredients — a possible tool for origin assignment and quality control

Relative carbon and nitrogen stable isotope abundances in total milk reflect the isotopic composition of the diet fed to the dairy cows; this diet and its δ-values depend on geographical and climatic factors. Milk from regions dominated by grassland typically shows relatively negative δ¹³C-values, while in regions dominated by crop cultivation the δ¹³C-values are more positive. The δ¹⁵N-values are influenced by factors such as soil conditions, the intensity of agricultural use and the climate. Casein in authentic milk samples is enriched in both ¹³C and ¹⁵N as compared to total milk, while the whey fraction is slightly enriched in ¹³C and depleted of ¹⁵N. The isotopic content of milk, casein and whey from one location have been measured throughout a period of longer than 1 year; variations are usually not greater than 1‰. In milk water, the ¹⁸O content was increased by between 2 and 6‰ as compared to ground water.     

Stable C and N isotope ratio analysis for regional geographical traceability of cattle in China

The aim of this study was to examine the variation in carbon and nitrogen stable isotope ratios in cattle tissues from different provinces in China, and to investigate the correlations of δ¹³C and δ¹⁵N values between different cattle tissues. Furthermore, the success rate of classification using δ¹³C and δ¹⁵N values to distinguish the geographical origin of cattle was analyzed. Fifty nine cattle samples were collected from Jilin, Ningxia, Guizhou and Hebei provinces in China, and the δ¹³C and δ¹⁵N values of de-fatted beef, crude fat and tail hair were measured using isotope ratio mass spectrometry (IRMS). There were highly significant regional differences in the mean values of δ¹³C and δ¹⁵N values in the cattle tissues. A significant correlation was found in δ¹³C and δ¹⁵N between de-fatted beef, crude fat and tail hair, which indicated that all of these matrices could be used to trace cattle to their geographical origin. The results of discriminant analysis showed that δ¹³C was the better indicator for cattle origin traceability than δ¹⁵N. The classification success rate could be improved greatly by combining the two indicators. It was concluded that stable isotope analysis of C and N in cattle tissue can be used to trace cattle diet and origin in China.     

Analysis of isotopic ratios for the detection of illegal watering of beverages

The applications of the stable isotope ratio analyses (D/H, ¹³C and ¹⁸O) in the assessment of watering in beverages such as wine and fruit juices are discussed in this study. The measurement of ¹⁸O/¹⁶O ratio in combination with D/H and ¹³C/¹²C ratio is mainly focused and the international official methods implementing stable isotope techniques will be mentioned. Furthermore, the ongoing study on a possible use of ¹³C/¹²C ratio of CO₂ to detect the addition of technical produced CO₂ in mineral sparkling waters is also presented.     

Assignment of raw material and authentication of spirits by gas chromatography, hydrogen- and carbon-isotope ratio measurements I. Analytical methods and results of a study of commercial products

Gas chromatography and the determination of natural isotope ratios are powerful analytical methods which can be used to check the authenticity of alcoholic beverages and to detect any adulteration. To check the origin and the authenticity of commercial fruit spirits, whiskies, etc., 197 samples were analysed by gas chromatography, ²H-NMR and ¹³C isotope mass spectrometry. The discrimination between different varieties was demonstrated by bivariate and multivariate discriminant analysis using different concentrations of volatile compounds such as methanol, butan-1-ol, 2- and 3-methyl-butanol, benzaldehyde and hexanol as well as isotopic data like (D/H)_I, (D/H)_II and ¹³C/¹²C isotopomers of ethanol. The results show that by using multivariate discriminant analysis it is possible to distinguish not only between different groups of spirits, e.g. those made of stone-fruit, malaceous fruit, grain and corn, but also between individual varieties, such as cherry, plum, mirabelle and apple. If the detection of highly rectified ethyl alcohol of agricultural origin and the identification of its raw materials are required, then natural isotope ratios are the only discriminant analytical parameters available.     

δ13C values and phytanic acid diastereomer ratios: combined evaluation of two markers suggested for authentication of organic milk and dairy products

Authentication of organic milk by suitable markers is currently attracting more and more interests in food control. In this study, we aimed to compare the efficiency of the markers stable carbon isotope ratio (δ¹³C value) with the SRR/RRR phytanic acid diastereomer ratio (SRR/RRR) of milk fat for distinguishing different feeding systems. For stable carbon isotope ratio analysis by elemental analysis–isotope ratio mass spectrometry (EA-IRMS), we first developed a simple sample preparation method based on milk fat extracts allowed to evaporate the solvent in tin capsules for liquid samples. The δ¹³C values and reproducibility measured with this alternative sample pre-treatment method excellently matched those obtained with the current standard method. Applied to milk samples, the results of the EA-IRMS analysis were linked to the SRR/RRR, and both markers allowed to distinguish milk from cows fed with hay (δ¹³C value > ?28.0 ‰, SRR/RRR <1.5) from feed used in conventional milk production which contained maize silage (C₄-plants) (p < 0.001). Milk fat of organic retail cheese samples was also highly depleted in ¹³C (δ¹³C value ?30.0 ‰ ± 1.1), and the SRR/RRR was low (<1.5). However, seven cheese samples showed inconsistent δ¹³C values and SRR/RRR, most likely due to the feeding of grass silage. Both parameters (δ¹³C values and SRR/RRR), together with the phytanic acid content of milk fat, also allowed distinguishing between the feeding of high amounts of pasture, hay, and/or grass silage.     

The potential for carbon dioxide formation during ripening of acid curd cheese

Inspired by recent reports on high concentrations of carbon dioxide in the atmosphere of ripening chambers used in acid curd cheese production, small-scale experiments were performed to systematically investigate sources of CO₂ formation. In a closed system with a ratio of cheese mass to air volume close to that in industrial scale, up to approximately 16% (v/v) CO₂ were observed within 3 d of maturation at 24 °C. Without addition of ripening salts (CaCO₃, NaHCO₃) the initial carbon dioxide formation was delayed, but maximum CO₂ levels were still much higher than admissible workplace concentrations. Control experiments with quarg, which was pasteurized for yeast inactivation, revealed that growth and activity of yeasts has to be considered as the most important source for carbon dioxide formation. The results of the study strongly point on the necessity of preventive measures for ensuring the safety of employees.     

Continuous dense‐phase CO2 processing of a coconut water beverage

Effects of dense‐phase CO₂ (DPCD) on microbial, physical, chemical and sensorial quality of coconut water (CW) beverage were evaluated. Pressure during DPCD treatment was not significant in microbial reduction whereas temperature and % CO₂ levels were significant. DPCD‐treated (34.5 MPa, 25 °C, 13% CO₂, 6 min), heat‐pasteurised (74 °C, 15 s) and untreated CW beverages were evaluated during 9 weeks of refrigerated storage (4 °C). Total aerobic bacteria of DPCD and heat‐treated samples decreased whereas that of untreated samples increased to >10⁵ CFU mL^?1 after 9 weeks. DPCD increased titratable acidity but did not change pH (4.20) and °Brix (6.0). Likeability of DPCD‐treated CW was similar to untreated. Heat‐treated samples were less liked (α = 0.05) at the beginning of storage. Off flavour and taste‐difference‐from‐control scores of heated samples were higher than DPCD during the first two weeks. DPCD extended shelf life of acidified, sweetened and carbonated CW over 9 weeks at 4 °C.     

Solubility of carbon dioxide in a seafood model product with fish oil

The solubility of carbon dioxide (CO₂) in a seafood model product with various amounts of salmon oil was investigated. Differential scanning calorimetry analysis of the salmon oil gave an onset temperature for crystallization at ?14.75 ± 0.74 °C, showing that the oil was in liquid state in the temperature range used in this experiment (1–8 °C). Solubility of CO₂ in salmon oil in liquid state was similar to water, with the same temperature dependency as water. Increased storage temperature decreased the amount of dissolved CO₂ and increased the headspace CO₂ and headspace gas volume. Headspace gas composition at equilibrium was linearly (R ² = 0.979) related to the composition of the packaging gas, while increasing CO₂ in the packaging gas increased the headspace gas volume and the amount of dissolved CO₂ in the product. When designing modified gas-packaging regimes for products with marine fat, sum of fat and water can be used to estimate the amount of dissolved CO₂ in the product.     

Investigating the impact of botanical origin and harvesting period on carbon stable isotope ratio values (13C/12C) and different parameter analysis of Greek unifloral honeys: A chemometric approach for correct botanical discrimination

The aim of this study was to investigate the impact of botanical origin and harvesting period on carbon stable isotope ratio (¹³C/¹²C), colour intensity (CI), radical scavenging activity (%RSA), P and Sn content of Greek unifloral honeys. Thus, twenty‐four honey samples were collected during harvesting periods 2011–2012 and 2012–2013, from four different regions in Greece. ¹³C/¹²C ratios and minerals were determined using isotope ratio mass spectrometry (IRMS) and inductively coupled plasma optical–emission spectroscopy (ICP‐OES), respectively. CI and %RSA were measured using spectrophotometric assays. Results showed that only ¹³C/¹²C values and %RSA were affected by both botanical origin and harvesting period (P < 0.05). Applying then chemometric analyses to the collected data set, honeys were correctly classified according to honey type (correct classification rate 87.5% and 79.2% using the original and cross‐validation method, respectively). The use of different origin parameters has the potential to aid in honey authentication.