Review of sodium analysis proficiency test results

Proficiency testing results for sodium analysis in foods raised concerns over the proportion of laboratories achieving satisfactory z-scores. Test materials for sodium analysis include fruit juice, canned meat meal, tomato sauce, cheese and pasta meal, and snack food. Fruit juice and tomato sauce data sets are the most problematic in deriving the assigned value with sufficiently low uncertainty to provide evaluative z-scores. The standard deviation for proficiency is derived from Horwitz, with a lack of collaborative trial data for these matrices to provide other guidance. The status of accreditation for the method/matrix does not appear to influence the observed variation in results. Microwave digestion is much less commonly used than simple acid digestion. The choice of determination method appears to be entirely matrix dependent (whether flame atomic absorption spectroscopy, flame photometry or inductively coupled plasma spectroscopy). Results for juice matrix may be overestimated if flame photometry is used, due to either potassium interference or careless reporting where potassium is also determined.     

Simultaneous analysis of Alternaria toxins and citrinin in tomato: an optimised method using liquid chromatography-tandem mass spectrometry

Alternaria toxins and citrinin are mycotoxins produced by fungi growing on different raw materials and agricultural commodities. Maximum levels of these toxins in foods are currently under consideration by the European Commission as a risk management measure. In this study, a new quantitative method is described for the determination of five Alternaria toxins and citrinin in tomato and tomato juice samples based on LC-MS/MS detection. Samples were extracted with pure methanol, followed by a derivatisation step with 2,4-dinitrophenylhydrazine to improve the determination of tenuazonic acid and to decrease the wide polarity difference between the compounds of interest. Samples were purified on hydrophilic-modified styrene polymer solid-phase extraction cartridges. High-performance liquid chromatographic columns packed with different core–shell materials were tested for the separation of toxins and a C-18 phase was in the final method applied to achieve sufficient separation of all relevant analytes. A key element of this approach was to prove successful transferability of the method to three different triple quadrupole mass spectrometers. A full single laboratory method validation was performed on two LC-MS/MS systems and performance characteristics met the predefined requirements. Moreover, the method was used in an international proficiency test and the satisfactory z-scores obtained (?0.1 to 0.8 in tomato juice samples) demonstrated the reliability of the approach described. The method will be validated in an inter-laboratory collaborative study and if the criteria for method precision are met, the method will be proposed as a new Work Item to the European Committee for Standardisation.     

甜菜品质分析方法研究：Ⅰ型保型澄清剂的研究

研究和比较了环保型澄清剂与传统的碱式醋酸铅澄清剂在利用冷水浸出法及火焰光度法测定糖分、钾、钠含量时的差异。分析表明，对含糖率、钾含量的测定，两种表剂的检测结果基本相同。因此，在检测上述３项指标时，环保型澄清剂完全可以替代碱式醋酸铅澄清剂，这对减少环境污染具有重要意义。     

Nondestructive determination of soluble solids content and pH in tomato juice using NIR transmittance spectroscopy

The potential of near-infrared (NIR) transmittance spectroscopy to nondestructively detect soluble solids content (SSC) and pH in tomato juices was investigated. A total of 200 tomato juice samples were used for NIR spectroscopy analysis at 800–2400 nm using an FT-NIR spectrometer. Multiplicative signal correction (MSC), and the first and second derivative were applied for pre-processing spectral data. The relationship between SSC, pH, and FT-NIR spectra of tomato juice were analyzed via partial least-squares (PLS) regression. PLS regression models were able to predict SSC and pH in tomato juices. The r _c, RMSEC, RMSEP, and RMSECV for SSC were 0.92, 0.0703°Brix, 0.150°Brix, and 0.138°Brix, respectively, whereas those values for pH were 0.90, 0.0333, 0.0316, and 0.0489, respectively. It is concluded that the combination of NIR transmittance spectroscopy and PLS methods can be used to provide a technique of convenient, versatile, and rapid analysis for SSC and pH in tomato juices.     

Evaluation of health-related composition and bioactivity of five fruit juices following Lactobacillus plantarum fermentation and simulated digestion

This study identified and compared the health-related components and bioactivity of five fruit juices following Lactobacillus plantarum NRRL-B-14768 fermentation and subsequent simulated gastrointestinal digestion. After 48-h fermentation, the vitamin C and total phenol content of orange juice, the polysaccharide content of watermelon juice and the content of functional elements in orange and tomato juices were relatively high. FTIR spectroscopy was used to reveal changes in phenols and organic acids. During fermentation, orange juice displayed the best 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) free radical scavenging capacities and inhibition of α-glucosidase (α-GC) and xanthine oxidase (XO), compared to the other fruit juices. After simulated gastrointestinal digestion, fermented orange juice had the highest vitamin C content, DPPH and ABTS free radical scavenging capacities and XO inhibitory activity, and fermented pineapple juice had the highest α-GC inhibitory activity. These results indicated the potential of these juices in producing fermented juice with high specific functionality.     

Evolution of Mineral Contents in Tomato Fruits During the Ripening Process After Harvest

A comparative study was carried out to evaluate the mineral content of tomato during ripening after harvest. Calcium (Ca), magnesium (Mg), sodium (Na), phosphorus (P), potassium (K), selenium (Se), and zinc (Zn) contents were determined in three of the main tomato types (round, elongated, and cherry) consumed in Portugal. Ca, Mg, Se, and Zn were determined by atomic absorption spectrometry, Na and K by flame photometry, and P by visible spectrometry. No significant variation was found in the Zn, P, Na, and K concentrations during the tomato ripening after harvest. For Ca, Mg and, especially, Se, significant variations in their corresponding concentrations were observed. The content of Ca and Mg tended to decrease from the initial concentration. Conversely, a considerable increase in Se content was observed. A decrease in total tomato mineral content was determined for all studied types after an 11-day period of maturation after harvest. Therefore, a new and significant aspect to emphasize as an outcome of this study is that an 11-day post-harvest ripening period for tomato ingestion by the final consumer should be recommended in order to benefit from the highest mineral content. This acquaintance could be very important for tomato agricultural practices and for economic development of this type of cultivation, as well as for the consumer’s health.     

Using Fish Sauce as a Substitute for Sodium Chloride in Culinary Sauces and Effects on Sensory Properties

Historically, fish sauce has been a standard condiment and ingredient in various Southeast Asian cuisines. Moreover, fish sauce imparts umami taste, which may enhance perceived saltiness in food. This quality suggests that fish sauce may be used as a partial substitute for sodium chloride (NaCl) in food preparation, which may present a valuable option for health‐conscious and salt‐restricted consumers. However, the degree to which NaCl can be decreased in food products without compromising taste and consumer acceptance has not been determined. We hypothesized that NaCl content in food may be reduced by partial replacement with fish sauce without diminishing palatability and consumer acceptance. Preparations of 3 types of food were assessed to test this hypothesis: chicken broth (n = 72); tomato sauce (n = 73); and coconut curry (n = 70). In the first session, the percentage of NaCl that could be replaced with fish sauce without a significant change in overall taste intensity was determined for each type of food using the 2‐Alternative Forced Choice method. In the second session, subjects rated 5 samples for each food with varying NaCl and/or fish sauce content on 3 sensory attributes: deliciousness; taste intensity; and saltiness. Our results demonstrate that NaCl reduction was possible in chicken broth, tomato sauce, and coconut curry at 25%, 16%, and 10%, respectively, without a significant loss (P < 0.05) in deliciousness and overall taste intensity. These results suggest that it is possible to replace NaCl in foods with fish sauce without reducing overall taste intensity and consumer acceptance.     

Antilisterial Properties of Marinades during Refrigerated Storage and Microwave Oven Reheating against Post‐Cooking Inoculated Chicken Breast Meat

This study evaluated growth of Listeria monocytogenes inoculated on cooked chicken meat with different marinades and survival of the pathogen as affected by microwave oven reheating. During aerobic storage at 7 °C, on days 0, 1, 2, 4, and 7, samples were reheated by microwave oven (1100 W) for 45 or 90 s and analyzed microbiologically. L. monocytogenes counts on nonmarinated (control) samples increased (P < 0.05) from 2.7 ± 0.1 (day‐0) to 6.9 ± 0.1 (day‐7) log CFU/g during storage. Initial (day‐0) pathogen counts of marinated samples were <0.5 log CFU/g lower than those of the control, irrespective of marinating treatment. At 7 d of storage, pathogen levels on samples marinated with tomato juice were not different (P ≥ 0.05; 6.9 ± 0.1 log CFU/g) from those of the control, whereas for samples treated with the remaining marinades, pathogen counts were 0.7 (soy sauce) to 2.0 (lemon juice) log CFU/g lower (P < 0.05) than those of the control. Microwave oven reheating reduced L. monocytogenes counts by 1.9 to 4.1 (45 s) and >2.4 to 5.0 (90 s) log CFU/g. With similar trends across different marinates, the high levels of L. monocytogenes survivors found after microwave reheating, especially after storage for more than 2 d, indicate that length of storage and reheating time need to be considered for safe consumption of leftover cooked chicken.     

Antioxidant capacity of tomato juice functionalised with enzymatically synthesised hydroxytyrosol

The antioxidant hydroxytyrosol has been enzymatically synthesised in order to functionalise tomato juice. The antioxidant capacity significantly increased in the functionalised juice according to a set of in vitro antioxidant assays (ie ferric thiocyanate method, inhibition of oxygen consumption, and scavenging of both DPPH^· and ABTS^·+ free radicals). In addition, hydroxytyrosol was stable within the tomato juice matrix under extreme storage conditions (room temperature and light exposure) for 48 days. Sensory properties (flavour and colour) of the tomato juice were not affected by functionalisation with hydroxytyrosol concentrations of up to 1 mg ml^?1. Therefore this functional tomato juice could be a promising source of health‐beneficial properties, beyond basic nutrition, taking into account both the high activity and bioavailability of hydroxytyrosol. © 2003 Society of Chemical Industry     

常见食品中钾、钠测定的方法研究

目的针对现行食品中钾、钠测定的国家标准的局限性,对食品中钾、钠测定的前处理方法和测定方法进行探讨。方法分别采用4种前处理方法和3种测定方法对普通食品和国家标准物质中的钾、钠进行测定,并计算和比较各种方法的检出限、精密度和准确度。结果 4种前处理方法测定钾、钠的平均回收率为84%~112%,精密度为0.4%~3.4%;3种测定方法测定钾、钠的检出限分别为1.79~10.7 mg/kg和3.68~14.2 mg/kg,精密度为0.2%~3.8%。结论 4种前处理方法和3种测定方法均能满足食品中钾、钠的检测要求,且无明显差异。密闭微波消解法和压力罐消解法更适合于钾、钠测定的前处理。在溶液酸度小于5%时,对于低含量的钾、钠,火焰原子吸收光谱法更为合适,而对于高含量的钾、钠,电感耦合等离子体发射光谱法更为合适。     

Effect of soy lecithin in enhancing fruit juice/sauce quality

Phosphatidylcholine is a major component of biological membranes and is an important mediator of physiological functions in mammals. In addition to biosynthetic routes of availability, phosphatidylcholine is also derived from the diet. The levels of phosphatidylcholine are quite low in fruits and fruit products. As the fruits ripen, the phospholipids are degraded into neutral lipids causing a drastic decline in phospholipid content. In the present study, we have evaluated the effects of external supplementation of soy lecithin on physico-chemical properties of tomato juice and sauce, as well as grape juice. The levels of protein, soluble solids and ash content were significantly enhanced by the addition of lecithin. The bulk viscosity of tomato juice and the sauce preparation was also enhanced by addition of lecithin. The yellow color values of the juice and sauce preparations were enhanced by lecithin. In grape juice preparations, the addition of lecithin did not cause any negative effects, but enhanced the solids content of the juice. Juice preparations with added lecithin were more stable than the controls. Lecithin may form complexes with pectin, lipids and other carbohydrates, affecting the food property and stability by various mechanisms.     

Inter-laboratory comparison study for pyrrolizidine alkaloids in animal feed using spiked and incurred material

Pyrrolizidine alkaloids (PAs) are hepatotoxic metabolites produced by plants. PAs in animal feed can cause acute or chronic intoxications in animals and can be transferred to milk. An inter-laboratory comparison study among 12 laboratories, using their own methods of analysis, was conducted for the detection and quantification of PAs in animal feed. The participants were asked to quantify PAs in a blank test sample, a blank test sample to be spiked with a provided spiking mixture of seven PA standards, and a test sample contaminated with common groundsel (Senecio vulgaris). Ten of the participating laboratories used an LC-MS/MS method, one used an LC-ToF-MS method, and one used a GC-MS method. None of the laboratories reported false-negative samples, while two laboratories reported false-positive results in the blank sample. z-scores were calculated for each laboratory for seven PAs in test samples B and C. z-scores varied considerably between laboratories for the concentrations of the free bases and less for the N-oxides, probably due to the lower levels of the free bases as compared with the N-oxides in the contaminated feed. Questionable or unsatisfactory results for the z-scores were obtained for 8% of the cases for the spiked sample and for 12% of the incurred sample. Three laboratories scored consequently positive or negative results. No preferred method for quantification of PAs in feed could be identified within the methods used for this study due to the relatively small number of participants. It was concluded that this inter-laboratory study shows that the methods used for PA detection need further development for accurate estimation of PAs in contaminated feed.     

Illumina Miseq高通量测序方法对袋装番茄酱微生物多样性分析

目的:研究袋装番茄酱的微生物多样性及差异。方法:采集番茄酱样品,采用Illumina Miseq-高通量测序方法对产自新疆地区的番茄酱进行测定,并结合计数方法对胀袋番茄酱中菌株进行计数和鉴定。结果:胀袋番茄酱中的腐败微生物为乳杆菌属微生物,正常番茄酱中鉴定出的微生物包括乳杆菌属、伯克氏菌属、劳尔氏菌属、草螺菌属、慢生根瘤菌等主要存在于植物和土壤中的细菌。结论:本研究为了解番茄酱制品的微生物多样性提供了一定的参考。     

Physicochemical parameters that influence carotenoids bioaccessibility from a tomato juice

In vitro digestion models have been developed to estimate carotenoid bioavailability but most do not consider that their diffusion from fruit matrix to the lipid phase of the bolus could be a limiting step. Therefore we designed a model in which tomato juice is mixed with oil or oil/water emulsions, and the carotenoids diffusing to oil are measured by spectrometry. Temperature, pH and tomato juice/peanut oil ratio were evaluated for their influence on carotenoid diffusion. When oil/tomato ratio was between 0.11 and 1, extraction of lycopene was limited by the saturation of the oil phase. With a large excess of oil, diffusion was also limited, as only 31 ± 1% of lycopene could be extracted from the juice. Diffusion did not vary significantly with pH but doubled when temperature rose from 10 °C to 37 °C.     

Comparative study of ion-selective electrodes versus flame emission photometry techniques for the determination of sodium and potassium in Spanish wines

The behaviour of sodium and potassium selective electrodes is described, using two analytical methods to determine the concentrations of both ions in sixty-three samples of red, rosé and white wines, taken from several wine growing areas in Spain. The analytical measurement technique adopted has been Multiple Known Addition, and the equipment used for this purpose has been the Autochemistry System Orion 960. Precision and accuracy of the recommended procedures, expressed in terms of the standard deviation and percentage of spike-recovery, are good and the results show a great concordance with those obtained by flame emission photometry, the reference technique.     

植物乳杆菌YSQ 规模化生产的低成本培养基配方优化

通过单因素试验、Plackett-Burman试验设计及响应面法筛选适于植物乳杆菌YSQ株大规模发酵的低成本培养基。结果表明：单因素试验确定培养基成分：碳源为玉米粉、次粉+蔗糖;氮源为豆粕;番茄汁作为生长因子供体。利用Plackett-Burman试验设计筛选出影响植物乳杆菌生长的4个主要因子：次粉、豆粕、K2HPO4和MnSO4。最陡爬坡、中心优化组合及响应面分析确定培养基各组分的最适添加量为：玉米粉10g/L、豆粕15.5g/L、次粉1.2g/L、蔗糖5g/L、番茄汁150mL/L、K2HPO4 1.1g/L、MnSO4 0.28g/L、MgSO4 0.3g/L。优化后,植物乳杆菌发酵18h的菌落总数从优化前的8.73×108CFU/mL(玉米粉、豆粕、次粉的混合料)提高到2.68×1010CFU/mL。     

Preference for salt in a food may be alterable without a low sodium diet

In response to current efforts to reduce population-wide dietary salt intake, the objective of this study was to determine whether liking for reduced sodium and low sodium tomato juice could increase following repeated exposure over an extended period. Eighty-three adult subjects participated in a three-part study: an initial taste test, a 16-week longitudinal study, and a final taste test. Subjects gave liking ratings of four tomato juice samples ranging in sodium from 640 mg (a concentration comparable to a commercially available product) to 136 mg per 237 ml serving (a low sodium concentration) at both taste tests. For the longitudinal study, subjects were divided into two balanced groups based on PROP sensitivity, hedonic sensitivity to salt, and motivation to reduce dietary salt intake; the abrupt group received tomato juice reduced in sodium to reach a low sodium target at week four, and the gradual group received juice reduced in sodium via difference thresholds to reach the same target at week 14. Though liking for the juice with the highest salt content was unchanged between taste tests, liking for all reduced salt juices increased at the final taste test relative to the initial taste test among subjects in both salt reduction groups. In addition, subjects in both groups experienced a downward shift in preference for salt in tomato juice, indicating that repeated exposure may be sufficient to alter preference for salt in a food in the absence of a low sodium diet. That salt preference may be altered by exposure alone within the context of a high salt diet is promising for both the food industry and individual consumers.     

番茄制汁的工艺条件优化及货架期预测模型的建立

目的优化番茄制汁工艺条件,建立货架期预测模型。方法以红熟且无破损的番茄等外果为主要原料,经去蒂、清洗、热烫去皮、破碎榨汁制成新鲜的番茄汁,研究在不同温度(5、27、37℃)贮藏对产品品质的影响;利用Arrhenius方程为基础,建立相关联动力学模型;研究感官评价、pH、番茄花青素含量、色差在不同储藏时间变化进行番茄汁货架期预测研究。结果 0.03%的黄原胶、0.10%的羧甲基纤维素钠、0.05%的琼脂片组成的复合稳定剂稳定效果最好,口感饱满可口、细腻爽滑,番茄香气清新浓郁。采用模糊权重法对番茄汁货架期间的多项品质指标不同的加权系数进行综合评定。品质综合评价的加权关联度=感官评分sensory×0.25+pH×0.25+番茄红色×0.25+色差×0.25。结论该模型可以用于番茄汁货架期预测。     

Chemical Characterization of Tomato Juice Fermented with Bifidobacteria

Abstract: The objective of this research was to characterize the chemical properties of tomato juice fermented with bifidobacterial species. Tomato juice was prepared from fresh tomatoes and heated at 100 °C prior to fermentation. Bifidobacterium breve, Bifidobacterium longum, and Bifidobacterium infantis were inoculated in tomato juice and kept at 35 to 37 °C for up to 6 h. Fructooligosaccharide (FOS) was added to tomato juice prior to fermentation. The analyses for brix, total titratable acidity (TTA), pH, color, and lycopene content were conducted to characterize tomato juices fermented with bifidobacterial species. Heat treatment of tomato juice did not cause any significant changes in brix, pH, and TTA. Only the redness of tomato juice was significantly increased, as the heating time increased to 30 min. The tomato juices fermented with B. breve and B. longum exhibited significant decreases in pH (3.51 and 3.80, respectively) and significant increases in TTA (13.50 and 12.50, respectively) (P < 0.05). B. infantis did not cause any significant change in the chemical properties of tomato juice. The addition of FOS further improved the fermentation of tomato juice by bifidobacterial species. The lycopene contents of tomato juice were significantly increased from 88 to 113 μg/g by heat treatment at 100 °C (P < 0.05), however did not exhibit any significant change after fermentation with bifidobacterial species.     

UTILIZATION OF RAPESEED MEAL IN SAUCE PRODUCTION

A sauce produced by fermenting rapeseed meal (RM) and wheat with Aspergillus oryzae and/or Aspergillus soyae for 1 yr was found comparable in its acceptability to a commercial soy sauce. During the fermentation the soluble solids in the liquor increased rapidly during the first 10 wk from 22.5% to 35.5% and then remained unchanged until the 40th wk when it again increased sharply to 40% by the 45th wk. The pH of the substrate decreased slowly from 5.5 to 4.9 after 40 wk of fermentation. A comparable RM sauce was produced using the semichemical method with 1 month fermentation. In this process, the soluble solids increased rapidly from 29% to 40% during the first 4 wk, then slowly to 42% after 12 wk. pH dropped from 5.5 to 5.2 after 5 wk of fermentation. The study showed that rapeseed meal could be used successfully as a soybean substitute in the sauce production.