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1.
Detection of juice-to-juice adulteration based on chemical composition studies is a common method used by government regulatory agencies and food companies. This study investigated the use of major carbohydrate (fructose, glucose and sucrose), polyol (sorbitol), proline, and phenolic profiles as indicators of pear adulteration of apple juice (PAAJ). For this work, a total of 105 authentic apple juice samples from 13 countries and 27 authentic pear juice samples from 5 countries were analyzed. Because the major carbohydrate ranges for these juices showed significant overlap their use as markers for PAAJ detection would be very limited. It was found that sorbitol and proline means for apple and pear were significantly different; however, their broad natural ranges would afford PAAJ at levels up to 30% without detection. In addition, careful selection of the pear juice used as the adulterant would further limit the usefulness of these markers for PAAJ detection. Arbutin was conclusively identified as a marker for pear juice on the basis of its presence in all 27 authentic pear samples and its absence (<0.5 microg/mL) in all 105 apple juice samples analyzed in this study. The application of the developed HPLC-PDA method for arbutin analysis to detect PAAJ at levels as low as 2% (v/v) was demonstrated. A confirmation method for the presence of arbutin in pure pear juice and apple adulterated with pear juice was introduced on the basis of the hydrolysis of arbutin to hydroquinone employing beta-glucosidase, with reactant and product monitoring by HPLC-PDA.  相似文献   

2.
The polymer-assisted reaction of 4-(hydroxymethyl)furan-2(5H)-one (4HM2F) with 21 carboxylic acids using polystyrene-carbodiimide (PS-carbodiimide) yielded an ester library. Four of the esters, (5-oxo-2,5-dihydrofuran-3-yl)methyl acetate (IS-1), (5-oxo-2,5-dihydrofuran-3-yl)methyl butyrate (IS-2), (5-oxo-2,5-dihydrofuran-3-yl)methyl 2-methylpropanoate (IS-3), and (5-oxo-2,5-dihydrofuran-3-yl)methyl chloroacetate (IS-4), were tested as internal standards for the quantification of patulin in apple juice by gas chromatography-mass spectrometry in the selected ion monitoring mode (GC-MS-SIM). The developed method combines an AOAC official extractive step and a GC-MS-SIM analysis. Using a chromatographic column containing trifluoropropylmethylpolysiloxane as the stationary phase and IS-1 as the internal standard, it was possible to perform an accurate and precise quantification of underivatizated patulin in apple juice at concentrations down to 6 microg/L. A detection limit of 1 microg/L was established.  相似文献   

3.
A procedure combining diphasic dialysis extraction with in situ acylation and gas chromatography/mass spectrometry (GC/MS) determination was developed for detection and quantification of the mycotoxin patulin in apple juice. Apple juice samples spiked with 4-N,N-dimethylaminopyridine were dialyzed using methane chloride and acetic anhydride inside dialysis tubing. Patulin was derivatized into its acetate and collected in the tubing after diphasic dialysis and was directly determined using GC/MS with the selective ion monitoring mode without further concentration and cleanup steps. Quantification was carried out by a calibration curve with an internal standard of correlation. The appropriate parameters of both dialysis and derivatization were examined. The linear range of the calibration curve was found to be 10-250 microg/L for patulin, and the limit of quantification was 10 microg/L. Levels of patulin ranging from 0 to 107.2 microg/L with 77-109% recovery were found in 10 apple samples. The technique combining diphasic dialysis extraction and acylation was demonstrated and showed potential for other applications.  相似文献   

4.
Patulin is a mycotoxin produced by mainly Penicillium species, for example, P. expansum, and Aspergillus species. There are several reports of patulin contamination in apple juice. Last year, the Ministry of Health, Labour and Welfare of Japan set the maximum allowable level of patulin in apple juice at 50 ppb and decided that the measurement of patulin levels in apple juice products should be conducted. To this end, a simple, accurate, and selective analytical method for the detection of patulin at levels lower than 5 ppb, the detection limit, is desired. This paper reports the development of an analytical method that employs solid-phase extraction-liquid chromatography-mass spectrometry (SPE-LC-MS). When MS measurements were conducted with the selected ion monitoring (SIM) mode, the pseudomolecular ions at m/z 153 and 156 were used to monitor patulin and (13)C(3)-labeled patulin, respectively. The detection limit (S/N = 3) and the quantification limit (S/N = 10) of patulin at injection levels into LC-MS were 12.5 and 25 pg, respectively. However, when the actual sample was applied for the analysis based on the developed method including the sample preparation, the detection limit (S/N = 3) and quantification limit (S/N = 10) were 2.5 and 5 pg in sample, respectively. The calibration curve obtained for concentrations ranging from 5 to 500 ppb showed good linearity with a coefficient of determination (r (2)) of 0.999. In addition, the recovery was >95% when an internal standard was used. The method was applied to the analysis of 76 apple juice samples from Japan, and as a result, patulin levels ranging from <1.0 to 45 ppb (detection frequency = 15/76) were detected. In this study, it was found that patulin was a greater contaminant in concentration/reduction than in "not from concentrate" apple juice.  相似文献   

5.
A rapid LC-MS method, which compares different mass analyzers-single quadrupole, ion trap, and triple quadrupole-was developed for the quantitative determination of isopropyl thioxanthone (ITX) in fruit juices. ITX, a photoinitiator in UV-cured inks that can reach foods from the cartons for beverages in which they are used, was extracted from fruit juice samples with acetone/hexane (50:50) using pressurized liquid extraction. This method gave detection limits of 3, 3, and 0.01 microg/L and quantification limits of 10, 10, and 0.05 microg/L using single quadrupole, ion trap, and triple quadrupole, respectively. Five replicate fortifications of different fruit juices at the quantification limit gave recoveries oscillating between 68 and 72% with CV varying between 14 and 18%. This is the first report of a positive mass spectrometric identification and quantification of ITX in fruit juice samples packed in TetraPack. The sensitivity and specificity of the LC-MS/MS analysis using the triple quadrupole enables it to be the method of choice for risk assessment and monitoring. The method was applied to apricot, orange, peach, apple, grape and pineapple, and cherry and strawberry juices and to fruit nectars from Spain and Italy, and the ITX was detected in the range of 0.05-0.78 microg/L.  相似文献   

6.
Microbially derived off-flavor is a major problem in apple juice production as it diminishes the sensory quality of the juice significantly. Fifteen relevant off-flavor compounds that are formed in apple juice, for example, by the strains Alicyclobacillus acidoterrestris and Actinomycetes (Streptomyces ssp.) were investigated with respect to their sensory relevance. The odor threshold values (i.e., detection and recognition values) were determined for all compounds in the matrix apple juice. Odor threshold values for fenchyl alcohol are reported here for the first time. The obtained values were set in relation to the limits of detection and quantification of a previously published GC-MS method. Eight tainted apple juice samples were analyzed for the presence of the 2 strains and the 15 off-flavor compounds. Both strains could be found in the samples; the presence of Streptomyces ssp. as spoilage bacteria of apple juice is reported for the first time. In samples with distinct off-flavor, 2-isopropyl-3-methoxypyrazine, 2-isobutyl-3-methoxypyrazine, 2-methylisoborneol, 1-octen-3-ol, fenchyl alcohol, geosmin, and guaiacol as well as 2,6-dibromophenol were determined in concentrations higher than the detection threshold.  相似文献   

7.
The equilibrium method is introduced for the detection of invert sugar addition to apple juice. The method consists of a pre-equilibration of the sample with dry pyridine at 50 degrees C for 20 min followed by the addition of trimethylsilylimidazole and heating at 75 degrees C for 40 min. The resulting derivatized carbohydrates are then analyzed by capillary gas chromatography. This method was successfully used by independent laboratories to distinguish heated pure, intentionally adulterated (with invert sugar), and intentionally adulterated and then heated apple juice concentrates. The equilibrium method was shown to give significantly lower coefficients of variation for this sample set when compared to the original capillary gas chromatographic method. In addition, these results indicate that it may also be an effective method for the detection of medium invert sugar, depending on the level of the fingerprint oligosaccharides in this sweetener.  相似文献   

8.
Fourier transform infrared spectroscopy and attenuated total reflection sampling have been used to detect adulteration of single strength apple juice samples. The sample set comprised 224 authentic apple juices and 480 adulterated samples. Adulterants used included partially inverted cane syrup (PICS), beet sucrose (BS), high fructose corn syrup (HFCS), and a synthetic solution of fructose, glucose, and sucrose (FGS). Adulteration was carried out on individual apple juice samples at levels of 10, 20, 30, and 40% w/w. Spectral data were compressed by principal component analysis and analyzed using k-nearest neighbors and partial least squares regression techniques. Prediction results for the best classification models achieved an overall (authentic plus adulterated) correct classification rate of 96.5, 93.9, 92.2, and 82.4% for PICS, BS, HFCS, and FGS adulterants, respectively. This method shows promise as a rapid screening technique for the detection of a broad range of potential adulterants in apple juice.  相似文献   

9.
There is a great interest in food components that possess possible health-protecting properties, as is the case with flavonoids. Previous research showed that conventional apple juice processing resulted in juices poor in flavonoids and with a low antioxidant activity. This paper shows that it is possible to improve flavonoid content in juice and its antioxidant activity by applying an alcoholic extraction either on the pulp or on the pomace. The levels of flavonoids and chlorogenic acid in enriched juice were between 1.4 (chlorogenic acid) and 9 (quercetin glycosides) times higher than in conventional apple juice. In enriched juice the antioxidant activity was 5 times higher than in conventional apple juice, with 52% of the antioxidant activity of the originating fruits present. The novel processing method had similar effects for three apple cultivars tested (Elstar, Golden Delicious, and Jonagold). The taste and color of enriched juice were different from those of conventional juice.  相似文献   

10.
A stable isotope dilution assay for quantification of pantothenic acid in food and blood plasma uses a 4-fold labeled isotopomer of the vitamin as an internal standard. Pantothenic acid and its labeled analogue were detected as trimethylsilyl derivatives by gas chromatography-mass spectrometry, showing a minimized spectral overlap. In starch a detection limit of 44 microg/kg, an intrasample relative standard deviation of 6.7%, and recovery values ranging between 97.5 and 99.4% were determined. Total pantothenic acid content was determined in rice, milk powder, apple juice, and blood plasma after enzymatic hydrolysis of the vitamin's conjugates; free pantothenic acid was quantified prior to enzyme treatment. Almost all results were found to be in good agreement with literature data.  相似文献   

11.
微波预处理原料对苹果汁褐变的影响   总被引：2，自引：0，他引：2  
为了防止苹果汁在贮藏过程中褐变,采用不同的微波功率和时间预处理原料苹果,研究微波预处理对苹果汁褐变的影响。结果表明,微波处理可以提高苹果汁的色值,降低多酚氧化酶的活性,引起氨基态氮含量的下降,并使苹果汁的酸度略微提高。在微波功率为720～900 W,处理时间75～125 s时,果汁色值较高。室温贮存45 d后,微波功率900 W,时间为100 s处理的果块,果汁色值为67.8,比未经微波处理的高91.5%。微波预处理是防止苹果汁褐变的一种简便安全、合理经济的加工方法。  相似文献   

12.
射频加热杀灭浓缩苹果汁中鲁氏接合酵母的工艺优化   总被引：1，自引：0，他引：1  
为研究射频对苹果汁中鲁氏接合酵母杀灭作用,该文以鲁氏接合酵母为试验菌株,通过单因素试验分析了射频加热时间、极板间距、果汁体积、果汁可溶性固形物对杀菌效果及果汁升温速度的影响。在固定果汁可溶性固形物为70%的条件下,通过响应面试验,建立了鲁氏接合酵母菌落总数降低对数值的二次多项数学模型,确定了在极板间距为110 mm、果汁体积40 m L、果汁可溶性固形物70%的条件下射频加热处理70 s,可以使果汁中鲁氏接合酵母菌落总数下降6个对数值以上。研究比较了相同样品经射频和传统水浴杀菌达到相同杀菌效果时,处理前后果汁理化指标及风味变化程度,结果表明,射频(70 s)比水浴(330 s)能更快达到杀菌目的,同时对果汁品质以及风味的影响(P0.01)小于水浴处理。研究结果为射频杀菌方面的深入研究及实际应用提供了参考。  相似文献   

13.
Spinosad is an insect control agent that is derived from a naturally occurring organism and is effective on a wide variety of crops, including citrus crops. A method is described for the determination of spinosad and its metabolites in citrus crops and orange processed commodities. The method determines residues of the active ingredients (spinosyns A and D) and three minor metabolites (spinosyn B, spinosyn K, and N-demethylspinosyn D). For dried orange pulp and orange oil, the method has a limit of quantitation (LOQ) of 0.02 microg/g and a limit of detection (LOD) of 0.006 microg/g. For all other sample matrices (whole fruit, edible fruit, juice, and peel), the method has an LOQ of 0.01 microg/g and an LOD of 0.003 microg/g. The analytes are extracted from the various sample types using appropriate solvents, and the extracts are purified by liquid-liquid partitioning and/or solid-phase extraction. All five analytes are determined simultaneously in the purified extracts by reversed-phase high-performance liquid chromatography with ultraviolet detection at 250 nm.  相似文献   

14.
The Alternaria mycotoxin tenuazonic acid was derivatized with succinic anhydride and conjugated to keyhole limpet hemocyanin (KLH) and to horseradish peroxidase (HRP), respectively. The KLH conjugate was used to produce polyclonal antibodies in rabbits. A competitive direct enzyme immunoassay (EIA) for tenuazonic acid was established, which was moderately sensitive for tenuazonic acid [50% inhibition concentration (IC(50)): 320 ± 130 ng/mL] but strongly reacted with tenuazonic acid acetate (IC(50): 23.3 ± 7.5 ng/mL). Therefore, an optimized EIA protocol was established, which employed acetylation of standard and sample extract solutions. The mean standard curve detection limit (IC(30)) for tenuazonic acid acetate was 5.4 ± 2.0 ng/mL, enabling detection limits for tenuazonic acid in apple and tomato products of 25-50 ng/g (150 ng/g in tomato paste). Recoveries in a concentration range of 50-2000 ng/g were 60-130% in apple juice and tomato juice and 40-150% in other tomato products. Tenuazonic acid was detected in apple juice and tomato products from German retail shops at levels of 50-200 ng/g. In conclusion, this novel EIA for tenuazonic acid could be useful within a screening program for Alternaria mycotoxins in food.  相似文献   

15.
The polyphenolic compositions of 31 Basque cider apple cultivars were determined in pulp, peel, and juice by high-performance liquid chromatography--diode array detection analysis of crude extracts and after thiolysis. Data sets, consisting of individual polyphenol concentrations, total procyanidin content, and the average degree of polymerization of procyanidins, were evaluated by multivariate chemometric techniques, to develop decision rules for classifying apple cultivars technologically into bitter and nonbitter categories. A preliminary study of the data structure was performed by cluster analysis and principal component analysis in each apple material. Bitter apple varieties presented higher contents of flavan-3-ols and/or dihydrochalcones than nonbitter cultivars. Different classification systems for the two categories on the basis of the chemical data were obtained applying several supervised pattern recognition procedures, such as linear discriminant analysis, K-nearest neighbors, soft independent modeling of class analogy, partial least-squares, and multilayer feed forward artificial neural networks. Excellent performance in terms of recognition and prediction abilities for both categories (100% of hits) was achieved in every case (pulp, peel, or juice). Polyphenolic profiles of apple pulp, peel, or juice provide enough information to develop classification criteria for establishing the technological group of apple cultivars (bitter or nonbitter).  相似文献   

16.
Patulin is a mycotoxin produced by certain fungi, such as those found commonly on apples. The patulin content of apple juice is a regulatory concern because patulin is a suspected carcinogen and mutagen. A simple model of the apple juice concentration process was carried out to examine the possible contamination of patulin in apple aroma, a distillate produced commercially in the concentration of apple juice. The results show no evidence for patulin volatility, and document a reduction in patulin content by at least a factor of 250 in the apple distillate obtained from apple juice. Furthermore, a survey of several commercial apple aroma samples found no evidence of patulin content.  相似文献   

17.
An on-line HPLC-DPPH screening method for phenolic antioxidants in apple methanol/water (80:20, v/v) extracts was applied. The determination of antioxidants was based on a decrease in absorbance at 515 nm after postcolumn reaction of HPLC-separated antioxidants with the 2,2'-diphenyl-1-picrylhydrazyl radicals (DPPH*). Each of the antioxidants separated by the HPLC column was observed as a negative peak corresponding to its antioxidative activity. The on-line method was applied for quantitative analysis of the antioxidants. A linear dependence of negative peak area on concentration of the reference antioxidants was observed. For validation of the on-line method the limit of detection, LOD (microg/mL), and the limit of quantification, LOQ (microg/mL), of the phenolic compounds were determined. Comparison of the UV and DPPH radical quenching chromatograms with authentic compounds identified catechin, chlorogenic acid, caffeic acid, epicatechin, and phloridzin in the apple cultivars (Lobo, Golden Delicious, and Boskoop), and the distribution of total antioxidant activity was calculated.  相似文献   

18.
A method for the direct determination of lead in evaporated milk and in fruit juice with no prior sample digestion was successfully collaborated by 13 laboratories. The anodic stripping voltammetric (ASV) method studied consisted of adding 0.2 mL aliquots of evaporated milk or 0.3 mL aliquots of fruit juice to 2.9 mL of a dechelating reagent, Metexchange. The reagent-sample mixture is then analyzed for lead by ASV with no further sample preparation. Each collaborator received 24 samples, 2 each at 5 different levels (0.07-0.70 ppm for spiked evaporated milk and 0.09-0.87 ppm for spiked apple juice) along with duplicate practice samples of labeled lead content at each of 2 levels for each sample type. All unknowns were coded with random numbers. Approximately 69% of the reporting laboratories had never analyzed either evaporated milk or fruit juice for lead. Average time between receipt of samples and reporting of results was 1.6 days for all laboratories. The pooled variations between duplicate determinations for apple juice and evaporated milk were 0.00059 and 0.00043, respectively. The method was adopted official first action for both fruit juice and evaporated milk.  相似文献   

19.
为了研究苹果汁中有机酸与掺假苹果汁的关系,从而通过检测有机酸进行质量控制和食品安全监督.该文共收集了340个中国产苹果样本并制成苹果汁,涉及14个试点种植区域的19个品种.通过高效液相色谱测定样本中有机酸的种类和含量.该试验通过添加水、L-苹果酸和蔗糖模拟制作原果汁含量分别为57％,50％和25％的掺假苹果汁.在测得的...  相似文献   

20.
A rapid method is described for the quantitative determination of patulin in apple juice. The mycotoxin is extracted from the sample with ethyl acetate and the extract is cleaned up by extraction with a sodium carbonate solution. Patulin is determined by reverse phase liquid chromatography using a muBondapak C18 column and a 254 nm ultraviolet detector. The lower detection limit in patulin standard solution is 0.32 ng and recovery is greater than 75%.  相似文献   

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