Optimized Extraction Method of Acetic Acid in Vinegar and Its Effect on SNIF-NMR Analysis to Control the Authenticity of Vinegar

Site-specific natural isotope fractionation by nuclear magnetic resonance (SNIF-NMR) is an accurate method for examining food adulteration. SNIF-NMR can be used to determine the ratio of deuterium to hydrogen (D/H) of a specific molecule position. Because the quantity of D differs between synthetic and fermented acetic acids, the method can be used to accurately monitor food adulteration. However, the effect of pretreated food on the results of SNIF-NMR has rarely been discussed. We present an extractive distillation method to increase the purity of acetic acid for fractionation; we used an orthogonal array experimental design to determine the optimal extraction conditions. We discuss the influence of extract solvents and sample concentration on the (D/H)_CH3 values calculated from the NMR results. The optimal conditions for extracting acetic acid were found to be a sample-to-solvent ratio of 1:1, seven extractions, and an extraction time of 15 min. The extraction rates for acetic acid were 93.65% and 80.57% when ethyl acetate and diethyl ether, respectively, were used. The acetic acid concentration of the ethyl acetate- and diethyl ether-extracted samples was further improved by distillation from 5 g/100 mL to 33.84 and 51.65 g/100 mL, respectively.     

Sodium benzoate and potassium sorbate preservatives in food stuffs in Iran

A high-performance liquid chromatography method was applied for the determination of the levels of benzoate and sorbate in 400 food samples, including pickled cucumbers, canned tomato pastes, sour cherry jams, soft drinks, fruit juices and dairy products (UF-Feta cheeses, Lighvan cheeses, lactic cheeses, yogurts and doogh). The results showed that 270 (67.5%) of all samples contained benzoate ranging from 11.9 to 288.5 mg kg^?1 in lactic cheese and fruit juice, respectively. The levels of sorbate in 98 (24.5%) of the samples were 20.1 to 284.3 mg kg^?1 in doogh and fruit juice, respectively. Moreover, benzoate was detected in all dairy products ranging from 11.9 mg kg^?1 in lactic cheese to 91.2 mg kg^?1 in UF-Feta cheese. A low concentration of benzoate could originate naturally, due to specific biochemical mechanisms during cheese, yogurt and doogh maturation. In conclusion, a minimum level for benzoate in dairy products should be defined in the legislation.     

Development of an Effective Treatment for A 5‐Log Reduction of Escherichia coli in Refrigerated Pickle Products

Refrigerated cucumber pickle products cannot be heat processed due to the loss of characteristic sensory attributes. Typically brined refrigerated pickles contain less than 100 mM acetic acid with pH values of 3.7 to 4.0. Refrigeration (4 to 10 °C) helps to inhibit the growth of spoilage bacteria and maintain flavor, texture, and appearance of the pickles. Previous research has shown that pathogenic Escherichia coli strains are unusually acid resistant and survive better in refrigerated acid solutions than at higher temperatures. We found that E. coli O157:H7 can survive for 1 mo or longer at 4 °C in brines typical of commercial refrigerated pickles. Our objective was to develop methods to assure a 5‐log reduction of pathogenic E. coli in these types of products, while maintaining the sensory characteristics. A novel brine formulation was developed, based on current commercial refrigerated pickle brines, which contained 25 mM fumaric acid, 5 mM benzoic acid, 70 mM acetic acid, and 342 mM (2%) sodium chloride, with a pH of 3.8. Sensory data indicate that this formulation did not affect flavor or other sensory attributes of the product, compared to traditional formulations. We achieved a 5‐log reduction of E. coli O157:H7 at 30 °C for 1.52 ± 0.15 d, at 20 °C for 3.12 ± 0.34 d, or at 10 °C for 8.83 ± 0.56 d. Growth of lactic acid bacteria was also inhibited. These results can be used by manufacturers to assure a 5‐log reduction in cell numbers of E. coli O157:H7 and Salmonella without a heat process during the manufacture of refrigerated pickle products. Practical Application : While refrigerated acidified vegetable products are exempt from the acidified foods regulations, we have shown that the vegetative microbial pathogens E. coli O157:H7 can survive for up to 1 mo in these products, given current commercial production practices. To improve the safety of refrigerated pickle products, a brine formulation with reduced acetic acid, but containing fumaric acid, was developed to assure a 5‐log reduction in cell numbers of E. coli O157:H7 without a heat process. The formulation can be used to assure the safety of refrigerated pickled vegetables without altering sensory characteristics.     

食醋中勾兑工业合成醋酸的调查分析

目的了解杭州地区市售食醋勾兑醋酸的现状,为今后质量监督执法和评价提供科学依据。方法对杭州地区流通领域的食醋进行了抽样检测分析,采用相关强制性国家标准进行判定。结果本次对杭州地区流通领域的61个食醋样品进行了勾兑合成醋酸检测分析,其中酿造食醋51个样品,配制食醋10个样品,根据GB1903—2008《食品添加剂冰乙酸(冰醋酸)》标准酿造醋酸比率(天然度)%≥95%判定,酿造食醋合格率为96.08%,配制食醋合格率为70.00%,配制食醋的掺假现象比酿造食醋严重。结论今后应进一步加强食醋勾兑合成醋酸的风险监测力度,确保食醋质量安全。     

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.     

Survival and Growth of Probiotic Lactic Acid Bacteria in Refrigerated Pickle Products

We examined 10 lactic acid bacteria that have been previously characterized for commercial use as probiotic cultures, mostly for dairy products, including 1 Pediococcus and 9 Lactobacilli. Our objectives were to develop a rapid procedure for determining the long‐term survivability of these cultures in acidified vegetable products and to identify suitable cultures for probiotic brined vegetable products. We therefore developed assays to measure acid resistance of these cultures to lactic and acetic acids, which are present in pickled vegetable products. We used relatively high acid concentrations (compared to commercial products) of 360 mM lactic acid and 420 mM acetic acid to determine acid resistance with a 1 h treatment. Growth rates were measured in a cucumber juice medium at pH 5.3, 4.2, and 3.8, at 30 °C and 0% to 2% NaCl. Significant differences in acid resistance and growth rates were found among the 10 cultures. In general, the acid resistant strains had slower growth rates than the acid sensitive strains. Based on the acid resistance data, selected cultures were tested for long‐term survival in a simulated acidified refrigerated cucumber product. We found that one of the most acid resistant strains (Lactobacillus casei) could survive for up to 63 d at 4 °C without significant loss of viability at 10⁸ CFU/mL. These data may aid in the development of commercial probiotic refrigerated pickle products.     

复合腌制剂对低盐腌渍黄瓜品质的影响

采用复合腌制剂对黄瓜进行低盐腌渍。通过单因素和正交试验,研究醋酸、甘露糖醇和乳酸钙添加量对低盐腌渍黄瓜的影响,以感官评分为评价指标,优化复合腌制剂腌渍工艺。结果表明,低盐腌渍黄瓜的复合腌制剂最佳组成为醋酸添加量0.1%、甘露糖醇添加量1.5%、乳酸钙添加量0.06%,在此优化条件下,复合腌制剂腌渍黄瓜的感官评分为94分。质构分析结果表明,复合腌制剂腌渍的黄瓜脆度优于低盐腌渍。     

Preservation of Acidified Cucumbers with a Natural Preservative Combination of Fumaric Acid and Allyl Isothiocyanate that Target Lactic Acid Bacteria and Yeasts

ABSTRACT: Without the addition of preservative compounds cucumbers acidified with 150 mM acetic acid with pH adjusted to 3.5 typically undergo fermentation by lactic acid bacteria. Fumaric acid (20 mM) inhibited growth of Lactobacillus plantarum and the lactic acid bacteria present on fresh cucumbers, but spoilage then occurred due to growth of fermentative yeasts, which produced ethanol in the cucumbers. Allyl isothiocyanate (2 mM) prevented growth of Zygosaccharomyces globiformis, which has been responsible for commercial pickle spoilage, as well as the yeasts that were present on fresh cucumbers. However, allyl isothiocyanate did not prevent growth of Lactobacillus plantarum. When these compounds were added in combination to acidified cucumbers, the cucumbers were successfully preserved as indicated by the fact that neither yeasts or lactic acid bacteria increased in numbers nor were lactic acid or ethanol produced by microorganisms when cucumbers were stored at 30 °C for at least 2 mo. This combination of 2 naturally occurring preservative compounds may serve as an alternative approach to the use of sodium benzoate or sodium metabisulfite for preservation of acidified vegetables without a thermal process.     

食醋掺假检验方法研究进展

食醋是一种传统的酿造调味品,当前食醋掺假的问题仍时有发生,食醋掺假检验方法的研究已成为当前调味品研究的热点之一。食醋掺假形式多种多样,掺假检验方法也各不相同,有的基于食醋特有的酿造组分如挥发性风味组分、有机酸、氨基酸等进行检验,有的通过检验食醋中掺入的非酿造组分如合成乙酸等进行识别。虽然当前食醋掺假检验方法研究取得了一定进展,但其实际应用尚不理想,将多指标组合使用识别食醋掺假可能是未来食醋掺假检验的重要方向。     

Lead Content in Canned Foods Containing Vinegar

The lead contents of various foodstuffs pickled and canned in vinegar were measured using ion selective analysis and microprocessor unit on pre-nitric acid digested samples. These included cucumber, sauerkraut, mixed pickles, leeks, and mustard greens. Where possible these values were compared with those of the fresh produce or the product pickled and stored in jars. In all cases studied, the fresh or bottled products showed levels well below the legal limit of 2 ppm (Food & Drug Act, Ottawa, 1975). In the case of the canned products all the lead levels were grossly in excess of the legal limit, varying from 5–10 ppm.     

Firmness Retention in Pickled Peppers as Affected by Calcium Chloride, Acetic Acid, and Pasteurization

Critical factors influencing firmness retention in pickled peppers were studied. The addition of CaCl, (0.2%, w/v, optimum) to whole, pickled‘Red Cherry’peppers increased firmness retention as determined by a puncture test using an Instron Universal Testing Machine. Pasteurization reduced firmness in the absence, but not in the presence, of added CaCl₂. CaCl₂ significantly (P ≤0.01) reduced softening during storage of‘Red Cherry’peppers at higher temperatures (36.7, 46.7°C), and resulted in a slight increase in firmness at 26.7°C. CaCI₂ did not significantly (P≥ 0.05) improve firmness retention in‘Jala-peno’peppers, but resulted in greater uniformity of firmness. CaCI, also improved firmness retention in pickled cucumbers. Firmness of unpasteurized peppers and cucumbers was not influenced significantly (P ≥0.05) by acetic acid concentrations of 2, 3 or 4%.     

Isotope Ratio Mass Spectrometry Coupled to Element Analyzer and Liquid Chromatography to Identify Commercial Honeys of Various Botanical Types

The aim of the present work was to investigate whether honeys of various botanical characteristics could be discriminated and identified on the basis of the isotopic data. For this purpose, 45 commercial honey samples of various botanical types were analyzed using isotope ratio mass spectrometry (IRMS) coupled to element analyzer (EA) and liquid chromatography (LC). δ ¹³C values of honey; corresponding extracted protein and individual sugars (sucrose, glucose, and fructose) of honey; reducing sugar; and sucrose contents were determined and utilized to demonstrate the authenticity of commercial honeys of different botanical types. Results indicated that a very strong correlation (δ ¹³C_protein = 0.862δ ¹³C_honey + 0.800, R ² = 0.944) was observed between δ ¹³C honey values and δ ¹³C protein values of real honey samples. δ ¹³C_honey and δ ¹³C_protein should range from ?27.2 to ?23.5 and ?26.9 to ?23.6‰ for pure honeys of various botanical types investigated in this study. The use of isotopic compositions and some systematic differences as authenticity criterion permits the honey samples of various botanical types to be reliably detected.     

Stable Isotope Ratios and Aroma Profile Changes Induced Due to Innovative Wine Dealcoholisation Approaches

The high ethanol level in wine has become an important issue for all the main wine producing countries. Several techniques are available to the wine industry to reduce the ethanol content; among them, the membrane contactors are certainly one of the newest. Very few studies on the effect of this practice on the wine quality and aroma profile and on the stable isotopes composition are available. A pilot and industrial plant equipped with the membrane contactor system were used in the study in the dealcoholisation on several white and red wines. Significant changes for several classes of aroma compounds in both pilot- and industrial-scale experiments were observed, even though these changes were not always in perfect agreement with the sensory evaluation carried out. Finally, modifications on the δ¹⁸O of up to 1?‰ for 2 %?v/v and of up to 4?‰ for 8 %?v/v ethanol removal were encountered. An increase of δ¹³C of ethanol of up to 1.1?‰ for 2 % and of up to 2.3?‰ for 4 % of dealcoholisation rate was also observed. Dealcoholisation via membrane contactor seemed to affect the overall wine composition (aroma and flavour), even though the main concern resided on the alteration of the isotopic composition which could be linked to product authenticity issues.     

Effects of acidic broth and juices on the growth and survival of verotoxin-producing Escherichia coli (VTEC)

Five verotoxin-producing non-O157:H7 Escherichia coli (VTEC) isolates (serotypes O26:H11, O91:H21, O111:H-, O145:H-, O174:H21) from hamburger and cattle, one O157:H7 clinical strain (human) and one O157:H7 strain isolated from cattle, were evaluated for their ability to grow in acidic broth. Luria Bertani (LB) broth supplemented with acetic or citric acid and adjusted to several pH values, were inoculated with stationary phase cultures of each strain, to determine the minimum pH for growth. This parameter depended upon the bacterial strain and the type and concentration of the organic acid used. The O91:H21 strain grew better in broth supplemented with 0.1 m acetic acid (pH 5.5) than both O157:H7 strains. Acetic acid exerted a greater antibacterial effect than citric acid at the same concentration and pH. Three strains (serotypes O91:H21, O111:H- and the O157:H7 clinical isolate) were incubated in apple cider vinegar, capsicum pickle brine and apple juice. All strains survived for<10 min in apple cider vinegar (0.8 m acetic acid) and <1 h in brine (0.4 m acetic acid). When exposed to apple juices, these serotypes displayed different behavior indicating that the O157:H7 strain had the lowest acidic resistance. We consider these findings useful for food manufacturers before designing a HACCP plan for acidic products.     

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.     

Discriminant Analysis of Selected Edible Fats and Oils and Those in Biscuit Formulation Using FTIR Spectroscopy

Recently, lard adulteration has highlighted the importance of checking raw materials and food products in order to assure their authenticity. Discriminant analysis (DA) using selected frequency regions (3,050?C2,800, 1,800?C1,600, and 1,500?C650 cm^?1) was exploited for the classification of lard and other commercial vegetable oils and animal fats. As a result, the Cooman plot showed that all vegetable fats/oils and animal fats, including lard, are clustered in a distinct group. DA was also employed to assign real food samples, in particular biscuit, into one of two groups. In addition, DA is a very useful means for Halal screening technique in order to enhance the Halal authentication process.     

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.     

Identification of Acacia Honey Adulteration with Rape Honey Using Liquid Chromatography–Electrochemical Detection and Chemometrics

The adulteration of honey is generally a concern of consumers and management departments of safety and quality. Adding low-price honey to high-price honey is often seen in the market. In this study, a reliable and simple method of liquid chromatography–electrochemical detection (LC-ECD) was presented to detect the adulteration of acacia honey which was added with rape honey at different levels (5–50 %, w/w). Chromatographic separation was carried out with a reversed phase column, and the mobile phase was methanol/2 % (v/v) aqueous acetic acid. Fingerprints of authentic honeys showed that the contents of chlorogenic acid were higher in acacia honey (1.738 mg kg^?1), while those of ellagic acid were much lower (0.274 mg kg^?1) in rape honey, so the chlorogenic acid and ellagic acid could be considered as possible markers of acacia and rape honeys, respectively. Samples were classified by cluster analysis and principal component analysis (PCA) according to the contents of phenolic acids. The results of PCA showed that chlorogenic acid and ellagic acid were the major variables, and no adulterated sample was identified as authentic honey. The results of cluster analysis (CA) indicated that the samples were appropriately divided into three main clusters, and adulterated samples were identified. Therefore, acacia honey adulteration with rape honey could be undoubtedly detected by LC-ECD combined with chemometric methods down to the level of 5 %.     

Effects of Salts and Preheating Temperature of Brine on the Texture of Pickled Cucumbers

The effects of salt type and preheating temperature on the texture and quality of pickled cucumber were studied. Four types of salt were used: bay salt, purified salt, and 2 prepared salts, 1 containing the same amount of Ca²⁺ and Mg²⁺ as those of bay salt, and the other containing a 3‐fold higher concentration of Ca²⁺ and Mg²⁺ than bay salt. Two different temperatures were used for the salt solutions: 98 °C and 65 °C. All samples were fermented for 30 d at 25 °C. To evaluate the quality of the pickled cucumber with fermentation, the pH level, total acidity, alcohol insoluble solids, and mineral contents were analyzed. Texture and sensory evaluation as well as a microscopic observation were performed to observe the textural change of the pickled cucumber during fermentation. Pickled cucumbers with 98 °C of preheated brine showed better texture than the ones with 65 °C. The pickled cucumbers brined with prepared salt, 1 which had the same amount of Ca²⁺ and Mg²⁺ to bay salt, displayed the best result among the samples tested, in terms of sensory, textural, and physical properties.