Some further studies on incubator reject eggs

Individual incubated and unincubated unfertilised eggs and 18-day incubator reject eggs have been measured by an improved assay for β-hydroxybutyric acid. Concentrations below 0.2 mg/100 g egg were found consistently for unfertilised eggs whether they had been incubated or not; 18-day incubator rejects included eggs with concentrations of β-hydroxybutyric acid up to 180 mg/100 g egg with a mean value of 13.8 mg/100 g egg. It is suggested that the different levels of β-hydroxybutyric acid can be approximately related to the embryological status of individual incubator reject eggs and the possible significance of this is discussed. Limiting the concentration of β-hydroxybutyric acid to not more than 0.2 mg/100 g in any sample of liquid whole egg would effectively preclude adulteration of fresh liquid whole egg with incubator reject eggs.     

Occurrence of Salmonella spp. in consumption eggs in Poland

The purpose of this study was to determine the prevalence of Salmonellae on egg shells in markets in Olsztyn, Poland. An investigation carried out by the Sanitary and Epidemiological Station into cases of food poisoning caused in Poland by Salmonella spp. in recent years showed that the largest number of outbreaks is connected with consuming foods containing hens eggs which had not undergone heat treatment, such as mayonnaise, creams, ice-cream and other products. The world egg production amounts to 400 billion, in Poland it reaches the level of around 8 billion per year. A total of 1200 eggs were purchased in 40 local markets in Olsztyn were examined for the presence of Salmonella between June 1997 and December 1998. Salmonella was not found on the shell or inside the eggs. From this study it would appear that the incidence of Salmonellae on eggs from Olsztyn shops is very low.     

Occurrence of Salmonella spp. in imported eggs into Albania.

Seventy-nine shell egg lots imported into Albania during the 2-years period 1996-1997 (69 lots during 1996 and 10 lots during 1997) were investigated for the presence of the Salmonella spp. Salmonella was detected in 1 out of 79 analysed pooled samples (1.26%). The Salmonella strain was isolated only from the egg shell, but not from the liquid part. The isolated strain was biochemically identified by the API 20 E system. Following biochemical identification, it was serotyped with Salmonella monovalent sera at the Institute of Public Health, Tirana, Albania and was found belonging to the Salmonella group C. The lot in which Salmonella was detected consisted of 275000 eggs.     

Occurrence of 2-ethylhexanoic acid in foods packed in glass jars.

After simultaneous distillation-extraction (SDE) of commercial baby foods (n = 20) and fruit juices (n = 15) (among them 15 and eight products labelled 'organic', respectively) from 11 different suppliers, analyses performed by coupled capillary gas chromatography-mass spectrometry (GC-MS) revealed the presence of 2-ethylhexanoic acid (2-EHA), a known teratogenic compound. 2-EHA was found in 80 and 73% of the baby foods and fruit juices, respectively. Amounts ranged from 0.25 to 3.2 mg kg(-1)(average, 0.55 mg kg(-1)) and from 0.01 to 0.59 mg l(-1) (average, 0.18 mg l(-1)) in baby foods and fruit juices, respectively. GC-MS analysis of the SDE extracts obtained from the plastic gaskets inside the metal lids of the samples under study revealed the gaskets to be the origin of 2-EHA. As shown from the non-contaminated samples under study, obviously technology is available to avoid 2-EHA contamination of glass jar-packed food.     

Occurrence of acetic acid and formic acid in breakfast cereals

Breakfast cereals are usually manufactured by extrusion followed by drying and toasting steps in which thermal treatments are applied. In addition, owing to the low water activity and the content in cereals of proteins and carbohydrates, precursors of the Maillard reaction, this reaction and degradation of sugars are favoured during processing. Acetic and formic acids have been identified as final products of Maillard reaction (MR) and sugar caramelisation. Acetic and formic acid contents have been determined by ion exchange high‐performance liquid chromatography in 56 commercial breakfast cereals. Results were evaluated taking into account the sample formulation. Acetic and formic acids were detected in all samples, and significant variations were observed for acetic acid depending on the protein and fibre content. Acetic acid, originating from 1‐deoxyglucosone cleavage during MR, proved to be a good indicator of processing in cereals enriched with or based on wheat flour because of their high protein content. Fibre addition increased acetic acid concentration. The application of acetic acid as a chemical marker of processing in breakfast cereals and its possible generation pathways are discussed. Copyright © 2006 Society of Chemical Industry     

Occurrence of 3-MCPD fatty acid esters in human breast milk.

A series of twelve breast milk samples were analysed by gas chromatography-mass spectrometry (GC/MS) operated in selected ion monitoring mode for 3-chloropropane-1,2-diol (3-MCPD). Whilst none of the samples contained 3-MCPD above the limit of detection of 3 microg kg(-1) milk, all contained high amounts of 3-MCPD esterified with higher fatty acids. The levels of 3-MCPD released by hydrolysis of these esters (bound 3-MCPD) ranged from the limit of detection (300 microg kg(-1), expressed on a fat basis) to 2195 microg kg(-1); with a mean level of bound 3-MCPD of 1014 microg kg(-1), which corresponded to 35.5 microg kg(-1) milk. The presence of bound 3-MCPD was confirmed using orthogonal gas chromatography coupled with high-speed time-of-flight mass spectrometry analysis for four randomly selected breast milk samples. Six breast milks collected from one of the nursing mothers 14-76 days after childbirth contained bound 3-MCPD within the range of 328-2078 microg kg(-1) fat (mean 930 microg kg(-1) fat). The calculated bound 3-MCPD content of these samples was within the range of 6 and 19 microg kg(-1) milk (mean of 12 microg kg(-1) milk). The major types of 3-MCPD esters were the symmetric diesters with lauric, palmitic, and oleic acids, and asymmetric diesters with palmitic acid/oleic acid among which 3-chloro-1,2-propanediol 1,2-dioleate prevailed.     

不同品种禽蛋中不饱和脂肪酸含量分析

目的比较鲜鸡蛋、鸭蛋和鹅蛋不同禽蛋的蛋清和蛋黄中的脂肪酸含量。方法实验分为鸡蛋组、鸭蛋组和鹅蛋组,用气相色谱法对各组禽蛋中的脂肪酸含量进行定量测定。结果 3种禽蛋蛋清中的饱和脂肪酸含量高于蛋黄,多不饱和脂肪酸含量低于蛋黄。ω-3不饱和脂肪酸含量大小为:鸡蛋鸭蛋鹅蛋,强化ω-3脂肪酸的鸭蛋中不饱和脂肪酸含量最高且ω-6/ω-3比值最低;熟鸭蛋的脂肪酸总量和饱和程度与鲜蛋相比没有发生显著性变化。但是咸蛋中饱和脂肪酸含量增加而不饱和脂肪酸含量减少。结论 3种禽蛋中脂肪酸含量不同,经强化的鸭蛋中有益ω-3多不饱和脂肪酸明显高于其他鸭蛋,营养价值最高。     

二十二碳六烯酸营养强化鸡蛋及蛋黄粉中 脂质分析

目的研究不同市售二十二碳六烯酸(docosahexaenoic acid, DHA)营养强化鸡蛋及蛋黄粉的脂肪酸组成以及DHA等n-3多不饱和脂肪酸的含量。方法脂质的提取采用Folch法,极性脂与中性脂的分离采用薄层色谱层析法,磷脂酶A2 (phospholipaseA2,PLA2)水解磷脂酰胆碱sn-2位脂肪酸,气相色谱法测定脂肪酸组成。结果市售普通鸡蛋中DHA含量为总脂肪酸的0.49%(29.19 mg/100 g鸡蛋),而4种不同品牌市售DHA营养强化鸡蛋中DHA占脂肪酸百分比分别为1.16%(111.79 mg/100 g鸡蛋)、1.86%(151.17 mg/100 g鸡蛋)、2.03%(159.46 mg/100 g鸡蛋)、5.37%(313.59 mg/100 g鸡蛋)。不同品牌的营养强化鸡蛋中DHA含量差异显著(P0.05)。市售DHA蛋黄粉中DHA含量为3.35 g/100 g蛋黄粉,其磷脂中含有2.07 g/100 g蛋黄粉。PLA2水解产物表明,蛋黄粉磷脂酰胆碱中DHA连接在磷脂酰胆碱sn-2位上。结论市售营养强化鸡蛋中的DHA含量高于普通鸡蛋,不同品牌的营养强化鸡蛋之间DHA含量差别较大。蛋黄粉磷脂酰胆碱中的DHA位置连接在sn-2位上。     

液相色谱-质谱联用测定鸡蛋中4-乙酰氨基苯甲酸的残留

目的 建立液相色谱-质谱法检测鸡蛋中4-乙酰氨基苯甲酸残留的方法.方法 样品经乙腈提取,通过式吸附净化和阴离子交换固相萃取净化,液相色谱分离,四极杆-静电场轨道阱质谱定性定量测定,平行反应监测模式检测,外标法定量.结果 4-乙酰氨基苯甲酸保留时间为5.6 min,在2.5～50μg/kg范围内呈现良好的线性关系,日内、...     

n-3脂肪酸鸡蛋营养价值分析

n-3类脂肪酸健康功效明确,其中EPA和DHA对降低心血管疾病风险等方面有较强作用,但人群摄入量往往不足.研究表明,通过对母鸡饲料进行n-3脂肪酸强化能有效地增加蛋黄内EPA和DHA的含量,其中DHA强化鸡蛋比未强化鸡蛋含量高2.4～10倍.每人每天食用1～2个n-3脂肪酸鸡蛋可使得机体每日摄入的EPA和DHA达到膳食推荐量.而由于n-3脂肪酸的引入,相应的安全性评估也应加强,包括需从n-3脂肪酸的摄入量、n-3脂肪酸鸡蛋里的深海鱼污染物和胆固醇含量等几个方面进行评价.     

Occurrence and role of lactic acid bacteria in seafood products

Lactic acid bacteria (LAB) in fish flesh has long been disregarded because the high post-mortem pH, the low percentage of sugars, the high content of low molecular weight nitrogenous molecules and the low temperature of temperate waters favor the rapid growth of pH-sensitive psychrotolerant marine Gram-negative bacteria like Pseudomonas, Shewanella and Photobacterium. In seafood packed in both vacuum (VP) and modified atmosphere (MAP) packaging commonly CO₂ enriched, the growth of the Gram-negative aerobic bacteria group (predominantly pseudomonads) is effectively inhibited and the number reached by LAB during storage is higher than that achieved in air but always several log units lower than the trimethylamine oxide (TMA-O) reducing and CO₂-resistant organisms (Shewanella putrefaciens and Photobacterium phosphoreum). Accordingly, LAB are not of much concern in seafood neither aerobically stored nor VP and MAP. However, they may acquire great relevance in lightly preserved fish products (LPFP), including those VP or MAP. Fresh fish presents a very high water activity (aw) value (0.99). However, aw is reduced to about 0.96 when salt (typically 6% WP) is added to the product. As a result, aerobic Gram-negative bacteria are inhibited, which allows the growth of other organisms more resistant to reduced aw, i.e. LAB, and then they may acquire a central role in the microbial events occurring in the product. Changes in consumers’ habits have led to an increase of convenient LPFP with a relative long shelf-life (at least 3 weeks) which, on the other hand, may constitute a serious problem from a safety perspective since Listeria monocytogenes and sometimes Clostridium botulinum (mainly type E) may able to grow. In any case the LAB function in marine products is complex, depending on species, strains, interaction with other bacteria and the food matrix. They may have no particular effect or they may be responsible for spoilage and, in certain cases, they may even exert a bioprotective effect in relation to undesirable bacteria. The bioprotective potential of endogenous LAB in relation to pathogens and spoiling bacteria has often been highlighted. However, the technology is still in its infancy compared with foods dairy and meat products in which either the carbohydrate content (dairy products) or sugar and salt added (meat products) favor the acidification by LAB that enable a natural preservation of the product. Successful studies on LAB as probiotic for fish intensify, but this potential is still to be explored for human. Although not usual, some applications of LAB for fermentation of marine products and by-products are described.     

蓄冷保温箱的研究进展

随着相变储能技术的发展,未来蓄冷保温箱将会更加环保、节能、耐用,并会对食品冷链运输产生积极的影响。文章综述了蓄冷保温箱所用的有机、无机和复合相变三类蓄冷剂,以及近年来国内外开发的微胶囊蓄冷剂、纳米蓄冷剂等新型蓄冷剂;从保温材料和温度场均匀性两方面阐述了蓄冷保温箱设计优化的进展,提出新型保温材料结构的可行性以及箱内温度场的影响因素。研发高效环保的蓄冷剂,优化的保温结构以及温度场均匀性是今后蓄冷箱研究的重点。     

Occurrence of 3-MCPD fatty acid esters in human breast milk

A series of twelve breast milk samples were analysed by gas chromatography-mass spectrometry (GC/MS) operated in selected ion monitoring mode for 3-chloropropane-1,2-diol (3-MCPD). Whilst none of the samples contained 3-MCPD above the limit of detection of 3 μg kg^?1 milk, all contained high amounts of 3-MCPD esterified with higher fatty acids. The levels of 3-MCPD released by hydrolysis of these esters (bound 3-MCPD) ranged from the limit of detection (300 μg kg^?1, expressed on a fat basis) to 2195 μg kg^?1; with a mean level of bound 3-MCPD of 1014 μg kg^?1, which corresponded to 35.5 μg kg^?1 milk. The presence of bound 3-MCPD was confirmed using orthogonal gas chromatography coupled with high-speed time-of-flight mass spectrometry analysis for four randomly selected breast milk samples. Six breast milks collected from one of the nursing mothers 14–76 days after childbirth contained bound 3-MCPD within the range of 328–2078 μg kg^?1 fat (mean 930 μg kg^?1 fat). The calculated bound 3-MCPD content of these samples was within the range of 6 and 19 μg kg^?1 milk (mean of 12 μg kg^?1 milk). The major types of 3-MCPD esters were the symmetric diesters with lauric, palmitic, and oleic acids, and asymmetric diesters with palmitic acid/oleic acid among which 3-chloro-1,2-propanediol 1,2-dioleate prevailed.     

Occurrence of 3-MCPD fatty acid esters in human breast milk

A series of twelve breast milk samples were analysed by gas chromatography-mass spectrometry (GC/MS) operated in selected ion monitoring mode for 3-chloropropane-1,2-diol (3-MCPD). Whilst none of the samples contained 3-MCPD above the limit of detection of 3 microg kg(-1) milk, all contained high amounts of 3-MCPD esterified with higher fatty acids. The levels of 3-MCPD released by hydrolysis of these esters (bound 3-MCPD) ranged from the limit of detection (300 microg kg(-1), expressed on a fat basis) to 2195 microg kg(-1); with a mean level of bound 3-MCPD of 1014 microg kg(-1), which corresponded to 35.5 microg kg(-1) milk. The presence of bound 3-MCPD was confirmed using orthogonal gas chromatography coupled with high-speed time-of-flight mass spectrometry analysis for four randomly selected breast milk samples. Six breast milks collected from one of the nursing mothers 14-76 days after childbirth contained bound 3-MCPD within the range of 328-2078 microg kg(-1) fat (mean 930 microg kg(-1) fat). The calculated bound 3-MCPD content of these samples was within the range of 6 and 19 microg kg(-1) milk (mean of 12 microg kg(-1) milk). The major types of 3-MCPD esters were the symmetric diesters with lauric, palmitic, and oleic acids, and asymmetric diesters with palmitic acid/oleic acid among which 3-chloro-1,2-propanediol 1,2-dioleate prevailed.     

Occurrence and content of hydroxycinnamic and hydroxybenzoic acid compounds in foods

Phenolic acid compounds seem to be universally distributed in plants. They have been the subject of a great number of chemical, biological, agricultural, and medical studies. Hydroxycinnamic acid compounds occur most frequently as simple esters with hydroxy carboxylic acids or glucose, while the hydroxybenzoic acid compounds are present mainly in the form of glucosides. Furthermore, phenolic acids may occur in food plants as esters or glycosides conjugated with other natural compounds such as flavonoids, alcohols, hydroxyfatty acids, sterols, and glucosides. Also, hydroxycinnamic acid amides appear to be common constituents. The occurrence of the different natural phenolic acid compounds in foods is reviewed, and data of the content in fruit, vegetables, and spices are given. The distribution of the main phenolic acid compounds in food plants as well as their changes during development and maturation of fruits are considered. Furthermore, the hydroxycinnamic acids bound to cell wall polymers, the phenolic acid compounds in coffee, cereals, oil seed, and tree nuts, and the analysis of phenolic acid derivatives are reviewed.     

Occurrence of biogenic amine-forming lactic acid bacteria in wine and cider

A collection of 810 lactic acid bacteria (LAB) strains isolated from wine and cider was screened for potential biogenic amine (BA) producers by combining molecular and phenotypic approaches. A newly developed multiplex PCR method allowed for the simultaneous detection of four genes involved in the production of histamine (histidine decarboxylase, hdc), tyramine (tyrosine decarboxylase, tyrdc) and putrescine (via either ornithine decarboxylase, odc, or agmatine deiminase, agdi) while TLC and HPLC analysis allowed for BA-production determination. One hundred and fifty-eight LAB strains were monitored by the molecular/phenotypic double approach and revealed a good correlation between genotypic and phenotypic data. Eighteen per cent of the tested strains were positive for at least one BA target gene with up to three detected simultaneously, in particular amongst Lactobacillus brevis and Lactobacillus hilgardii isolates for the tyrdc and agdi genes. The most frequent gene corresponded to the agdi gene detected in 112 strains (14% of all LAB strains) of 10 different LAB species. The tyrdc gene was detected in 67 strains represented by 7 different LAB species (8% overall), especially those isolated from wine. Lower levels of hdc⁺ (2% of strains) and especially odc⁺ (0.5% of strains) strains were observed. Interestingly, species that have never been described to carry BA-producing pathway genes were identified in this study. Furthermore, only one cadaverine-producer was detected and corresponded to Lactobacillus 30a, a collection strain not found in fermented beverages, although cadaverine is commonly detected in wines.