The influence of hydrophobic substances on water vapor permeability of fish gelatin films modified with transglutaminase or 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)

The effect of different hydrophobic substances on water vapor permeability (WVP) of unmodified fish gelatin films and cross-linked with transglutaminase (TGase) or with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) was determined. Both unmodified and cross-linked films were characterized by very poor water barrier properties. Amaranth oil, rapeseed oil, lanolin, beeswax and ozococerite at concentration of 10% decreased WVP of unmodified gelatin films by 42, 15, 37, 53 and 36%, respectively. Increasing concentration of these substances up to 60% caused further improving of the water barrier properties. Addition of lecithin into film-forming emulsions prevented separation of lipid layer on the film surface. Among unmodified films with lecithin and 60% of lipids the highest decrease of WVP was found in case of amaranth oil and beeswax, by 73 and 87%, respectively, in comparison to only-gelatin films. WVP of chemically modified films in the presence of 60% of beeswax with addition of lecithin was decreased by about 65%. Enzymatically modified films with beeswax were very brittle and broke during analyzes, similarly as those with amaranth oil and lecithin. WVP of enzymatically modified films with lecithin and 60% of rapeseed oil and lanolin was respectively, about 60 and 47% lower than that of films without hydrophobic substances.     

The water vapour permeability,mechanical properties and solubility of fish gelatin–chitosan films modified with transglutaminase or 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and plasticized with glycerol

The effect of glycerol on the mechanical and water barrier properties, as well as on the water solubility, of fish gelatin–chitosan films (4:1, w/w) cross-linked with TGase or EDC was determined. The addition of glycerol in concentrations up to 30% (of the substrate mass) to the fish gelatin–chitosan films modified with TGase or EDC did not change their solubility in buffers of pH 3 and 6 at 25 °C or during heating at 100 °C for 60 min. The chemical and enzymatic cross-linking of the components did not increase the water barrier properties of the films. WVP of the films modified with EDC and TGase was not affected by glycerol at concentrations up to 25% of the substrate mass. Tensile strength of the films decreased after modification of the components with TGase or EDC, respectively, by about 25% and 40%. The elongations of the enzymatically modified films containing 20% of glycerol and of chemically modified films containing 15% of glycerol were, respectively, about 8 and 13 times higher than those of unplasticized films; however, the tensile strengths of plasticized films were, respectively, 2.5 and 5 times lower.     

The effect of pH on the gelling behaviour of canola and soy protein isolates

The present study investigates the gelation mechanisms of a canola protein isolate (CPI) as a function of a pH (3.0–9.0), and compares it to that of a commercial soy protein isolate (SPI). A rheological investigation found that CPI was non-gelling at pH 3.0, and then formed a gel with increasing strength as pH was raised from pH 5.0 to 9.0. In contrast, the commercial SPI ingredient was found to be non-gelling at pH 9.0, but formed the strongest networks at pH 5.0 near its isoelectric point (pI = 4.6). Denaturation temperature as determined by differential scanning calorimetry were found to occur at ~ 78 °C for CPI at pH 5.0, then shifted to higher temperatures (~ 87 °C) at pH 7.0/9.0, whereas detection of SPI denaturation could not be obtained due to instrument sensitivity. Gelling temperatures were similar for both CPI and SPI (~ 82–86 °C) at all pHs, with the exception of SPI at pH 5.0 (~ 46 °C). Overall CPI networks were stronger than SPI, since the latter had weaker inter- and intramolecular junction zones. Confocal laser scanning microscopy images indicated that CPI gels became denser with lower lacunarity values as pH increased from 3.0 to 9.0. Moreover, the fractal dimension of CPI gels was found to increase from ~ 1.5-1.6 to ~ 1.8 as pH increased from 5.0/7.0 to 9.0, respectively suggesting diffusion-limited cluster-cluster aggregation. Images of SPI networks were not concurrent with fractal analysis under the conditions examined. Despite CPI having excellent gelling properties that are comparable to SPI, its need for alkaline pH conditions will limit its applicability in foods.     

Production of low-salt restructured fish products from Mexican flounder (Cyclopsetta chittendeni) using microbial transglutaminase or whey protein concentrate as binders

Mexican flounder (Cyclopsetta chittendenni) is an abundant fish specie usually caught as shrimp by-catch in the north of the Gulf of Mexico, but due to its small size is mostly discarded after dying during catching and handling operations. The objective of this work was to determine the feasibility of obtaining low-salt restructured fish products using flounder flesh as raw material. Two levels of salt (10 and 20 g/kg) were tested and microbial transglutaminasa (MTGase) (3 g/kg) or whey protein concentrate (WPC) (10 g/kg) were used as binders. Changes in mechanical properties (texture profile analysis and puncture test), expressible water and colour attributes were measured. Good gels from Mexican flounder were obtained at both salt levels. The use of MTGase improved the mechanical properties at both salt levels. However, WPC improved the mechanical properties of gels obtained only with 20 g salt/kg. The restructured fish products showed a light greyish colour adequate for commercialization.     

Comparison of gelling properties and flow behaviors of microbial transglutaminase (MTGase) and pectin modified fish gelatin

The gelling and structural properties of microbial transglutaminase (MTGase) and pectin modified fish gelatin were compared to investigate their performances on altering fish gelatin properties. Our results showed that within a certain concentration, both MTGase and pectin had positive effects on the gelation point, melting point, gel strength, textural, and swelling properties of fish gelatin. Particularly, low pectin content (0.5%, w/v) could give fish gelatin gels the highest values of gel strength, melting temperature, and hardness. Meantime, flow behavior results showed that both MTGase and pectin could increase fish gelatin viscosity without changing its fluid characteristic, but the latter gave fish gelatin higher viscosity. Both MTGase and pectin could increase the lightness of fish gelatin gels but decreases its transparency. More importantly, fluorescence and UV absorbance spectra, particle size distribution, and confocal microscopy results indicated that MTGase and pectin could change the structure of fish gelatin with the formation of large aggregates. Compared with MTGae modified fish gelatin, pectin could endow fish gelatin had similar gel strength, thermal and textural properties to pig skin gelatin.     

英国农业渔业食品部对酱油和同类产品中3-氯-1.2-丙二醇的检测

欧洲共同体食品安全与标准组织(ＪＦＳＳＧ)的出版物于1999年8月31日通报了在英国买到的酱油及同类产品中3—ＭＣＰＤ的测定结果。1999年8、9月从零售商买到大豆酱油、蘑菇酱油、蚝油及其它酱油40个样品,用检验限度为001ｍｇ/ｋｇ的法定方法测定。测定值与食品顾问委员会(ＦＡＣ’Ｓ)的推荐值进行比较,下面的报告表明一些牌子的酱油含3—ＭＣＰＤ的含量比较高。(在其它欧洲国家采样)。1　样品的检测表1　酱油与相关产品中3—ＭＣＰＤ测定值1999年3—ＭＣＰＤｍｇ/ｋｇ样　品　数　目总样品数酱油其它产品未检出21165001～010ｍｇ/ｋｇ523010…     

吡咯基丝氨酸乙酯的合成表征及其对大蒜绿变的作用

采用有机合成的方法得到新化合物吡咯基丝氨酸乙酯,验证其是否可以作为大蒜绿变的色素前体,并用核磁共振的方法验证了这种新化合物具有和已报导过的大蒜绿变色素前体-3,4-二甲基吡咯基缬氨酸(PP-Val)和3,4-二甲基吡咯基丙氨酸(PP-Ala)相似的结构,只是R侧链的结构不同.但实验结果表明,吡咯基丝氨酸乙酯不能使新蒜绿变,也不能和丙酮酸发生反应,表明R侧链的结构对这种吡咯基氨基酸是否能作为色素前体起着很重要的作用.     

Xylose-lysine model systems: The effect of pH on the volatile reaction products

Aqueous molal solutions of xylose and lysine (initial pH 4–9) were refluxed either with control of the pH at 5–0 or without pH control (final pH 2–6). Analysis by gas chromatography (GC) and GC-mass spectrometry resulted in the identification of 58 and 28 compounds, respectively, from the two systems. Furans were the main reaction products in both systems and 2-furfural alone comprised 522 and 999 g kg^?1 of the volatiles, respectively, from the systems with final pH values of 5–0 and 2–6. Maintaining the pH at 5–0 resulted in a higher yield and greater numbers of nitrogen-containing compounds, and monocyclic pyrroles, pyridines and 2,3-dihydro-l H-pyrrolizines were identified only in that system. Aliphatic compounds, alicyclic compounds, benzene derivatives. l-(2–furfuryl)pyrroles and pyrazines were also identified. This investigation is the first report of the formation of 2.3-dihydro-l H-pyrrolizines in a model system containing lysine as the amino compound; a possible mechanism is proposed.     

Improvement on production of (R)-4-chloro-3-hydroxybutyrate and (S)-3-hydroxy-gamma-butyrolactone with recombinant Escherichia coli cells

(R)-4-Chloro-3-hydroxybutyrate (CHB) and (S)-3-hydroxy-gamma-butyrolactone (HL) are used for the synthesis of biologically and pharmacologically important compounds. Enterobacter sp. DS-S-75 was found to have the unique activity to convert (S)-CHB in the racemate to (S)-HL through asymmetric dechlorination, hydrolysis, and lactonization. As a result, the remaining (R)-CHB and formed (S)-HL could be obtained in a one-pot reaction. We purified the CHB degrading enzyme which catalyzing these reactions and isolated the coding gene from the strain DS-S-75 in order to improve the productivity of these compounds using the transformant. Interestingly, the purified enzyme showed not only dechlorinating, but also hydrolyzing activities on CHB and the similar carboxylic esters, it was then designated CHB hydrolase, and appears to be a novel enzyme. The gene had 1101 bp encoding 367 amino acids including a signal peptide composed of 25 residues. The deduced amino acid sequence contained a conserved region generally found in esterases and lipases, but did not have significant similarity. When asymmetric degradation of racemic methyl CHB (CHBM) was performed using a culture broth of Escherichia coli DH5alpha transformed with the isolated gene, the reaction time was shortened 20-fold over that of the strain DS-S-75, and the maximum concentration of the substrate could be increased from 8% to 15% (w/v). Moreover, both of the obtained residual (R)-CHBM and the formed (S)-HL had high optical purities (>99% e.e.).     

市场零售水产品（鱼类）真实属性情况分析与监管建议

目的 对市场零售水产品（鱼类）进行物种鉴定,调查分析其真实属性。方法 以COⅠ基因为目标基因,应用DNA条形码技术鉴别深圳零售渠道水产品（鱼类）的品种来源。结果 根据BOLD系统鉴定结果统计,120份深圳地区市场零售水产品（鱼类）样品中,存在以异鳞蛇鲭冒充金枪鱼的现象,部分水产品类别范畴不清晰,虹鳟等钩吻鲑属鱼类是否明确归入“三文鱼”类存在争议。结论 目前深圳市场零售水产品（鱼类）存在鱼种替代或标签不合规现象,建议加强监管、持续规范市场秩序。     

发酵液中3-甲硫基丙醇的GC-MS分析

研究建立发酵液中3-甲硫基丙醇的GC-MS分析检测方法.我们通过GC-MS分析比较了不同的有机溶剂(二氯甲烷、正己烷、乙醚、乙酸乙酯、石油醚等)及不同的萃取体积比对试验造成的影响,结果发现二氯甲烷是最合适的萃取试剂,最佳萃取体积比为二氯甲烷∶发酵液=1∶2;比较不同极性色谱柱、不同分流比以及不同载气流速的GC-MS检测3-甲硫基丙醇效果,确定弱极性色谱柱TR-1MS、分流比15∶1、载气流速1.0mL/min为其最佳检测条件.     

High pressure effect on the color of minced cured restructured ham at different levels of drying, pH, and NaCl

Color changes of minced cured restructured ham was studied considering the effects of high pressure (HP) treatment (600 MPa, 13 °C, 5 min), raw meat pH₂₄ (low, normal, high), salt content (15, 30 g/kg), and drying (20%, 50% weight loss). Raw hams were selected based on pH₂₄ in Semimembranosus, mixed with additives, frozen, sliced, and dried using the Quick-Dry-Slice® process. Meat color (CIE 1976 L*a*b*) and reflectance spectra were measured before and after HP treatment. HP significantly increased L*, decreased a*, and decreased b* for restructured ham dried to 20% weight loss, regardless of salt content and pH₂₄. L* and a* were best preserved in high pH/high salt restructured ham. HP had no effect on the color of restructured ham dried to 50% weight loss. HP had no effect on the shape of reflectance curves, indicating that the pigment responsible for minced cured restructured ham color did not change due to HP.     

Stability of sorbates in the presence of EDTA: effect of pH,packaging material and sequestrant level

The effect of pH (3.5 or 5.0), packaging material (glass or polyethylene terephthalate, PET) and EDTA level (0.075 or 0.500 g kg^?1) on sorbate stability in model aqueous systems was studied. At pH 3.5, the addition of 0.075 or 0.500 g kg^?1 of EDTA showed a protective effect on sorbate stability in both types of packaging materials studied. In contrast, at pH 5.0 and using PET flasks, no effect of EDTA was observed. However, when the systems were packed in glass, EDTA presence increased sorbate degradation. The latter trend might be attributed to the greater iron scavenging ability exhibited by EDTA in those conditions. According to observed trends, in order to minimize sorbate destruction at pH 3.5, the use of glass flasks is recommended and an EDTA level of 0.075 g kg^?1. At pH 5.0, however, it is better to use PET flasks, and in these conditions EDTA addition did not influence preservative destruction. The results stress the importance of considering the interactions between system pH, additives, level of use and packaging material in relation to food stability of new formulated products. Copyright © 2004 Society of Chemical Industry     

Reactive Maillard intermediates leading to coloured products — 5-hydroxymethyl- and 5-(1,2-dihydroxyethyl)-3(2H)-furanone

In the course of the Maillard reaction, labile sugar degradation products are formed that are susceptible to secondary reactions and therefore have a decisive influence on the product spectrum. Such reactive intermediates may be transformed into stable derivatives with trapping reagents, and thus be protected from further reactions. Secondary processes may also be forestalled if the primary products are removed from the reaction mixture by high-vacuum distillation. By this procedure, 5-hydroxymethyl- and 5-(1,2-dihydroxyethyl)-3(2H)-furanone have been identified directly from Maillard reaction mixtures for the first time. The activated methylene group of these 3(2H)-furanones can easily enter into condensation reactions. The coloured condensation products in turn react with primary amines to pyrrolinone derivatives, which may also contribute to the colouring observed in non-enzymatic browning.     

Effect of high‐pressure treatments on mechanical and functional properties of restructured products from arrowtooth flounder (Atheresthes stomias)

Restructured fish products from arrowtooth flounder (Atheresthes stomias), an abundant and subutilized species from the Gulf of Alaska, were obtained by hydrostatic pressure processing (HPP) at 400 and 600 MPa with 0–5 min pressure‐holding time. Minced fish meat was massaged with 20 g kg^?1 salt at 10 °C during 5 min, stuffed in commercial sausage case and HPP‐treated. Raw and cooked (90 °C for 15 min) pressure‐treated gels were characterized by changes in mechanical properties (texture profile analysis and punch test), protein solubility, electrophoretic profile, expressible water and color. The mechanical properties of raw fish gels increased with pressure level and pressure‐holding time while solubility decreased. Myosin aggregation shown by SDS‐PAGE was associated with changes in mechanical and functional properties. The values for mechanical properties of heat‐induced gels were higher in cooked pressure‐treated samples than in the heat‐only control. Copyright © 2004 Society of Chemical Industry     

Effect of salt and transglutaminase (TG) level and processing conditions on quality characteristics of phosphate-free, cooked, restructured pork shoulder

Six treatments of phosphate-free restructured cooked pork shoulder were produced with two salt levels (2% and 1%) and three transglutaminase levels (0%, 0.075% and 0.15%) under two processing conditions (72 °C/65 min and 78 °C/65 min). Salt level significantly affected (p < 0.05) the chemical composition, the cooking losses, the colour, the sensory attributes and the overall acceptability of the product. Transglutaminase level affected (p < 0.05) only the consistency and the overall acceptability. The processing conditions on the contrary, affected the moisture and the protein content, the cooking losses, the consistency and the juiciness of restructured cooked pork shoulder. Transglutaminase can be used at a level of 0.15% with reduced salt level (1%) and processing at 72 °C/65 min to produce phosphate-free restructured cooked pork shoulder with acceptable sensory attributes.     

The perfluoroalkyl substance (PFAS) contamination level in milk and milk products in Poland

Cross-sectional studies concerning the contamination of milk and milk products by perfluoroalkyl substances (PFASs) are presented and the extent of contamination that may occur in food samples, collected in Poland in 2016 is evaluated; not only milk, cottage cheese, natural yoghurt and butter but also previously untested foods, including kefir, sour cream and Camembert-type cheese. Levels of 7 perfluoroalkyl carboxylic acids (PFCAs) and 3 perfluoroalkane sulfonates (PFSAs) were analysed using the QuEChERS extraction method followed by micro-HPLC-MS/MS. All PFASs were detected with an RSD of lower than 10%. The most commonly detected was perfluorooctanoic acid, followed by perfluorobutanoic acid and perfluorohexane sulfonate, on par with perfluorooctane sulfonate. The largest contributor to the total PFAS concentration in the investigated food samples was perfluorobutanoic acid, and its summary concentration within the group was estimated to be 13.34 ng g⁻¹. The results for 43.4% of samples analysed were greater than LOQ (limit of quantification).     

Impact of salt, phosphate and temperature on the effect of a transglutaminase (F XIIIa) on the texture of restructured meat

The effect of the transglutaminase F XIIIa on texture parameters was analysed in meat model systems simulating a restructured meat product. Porcine M. longissimus dorsi at normal ultimate pH was obtained 2 days post mortem from pigs slaughtered at approx. 100 kg liveweight. The F XIIIa product used was a recombinant protein produced by fermentation of Saccharomyces cereviciae. In raw minced meat F XIIIa increased cohesion, hardness and elasticity when a time-temperature heat treatment of 37 °C and 90 min was used during processing, while processing at 10 °C for 23 h caused only minor texture changes. Salt and phosphate addition together with F XIIIa resulted in a remarkable increase in binding properties. Thus, the texture parameters increased particularly at salt levels between 2 and 4% and a phosphate level of 0.2%. Binding of meat pieces containing 0.2% phosphate, 1% salt and F XIIIa as 0.4% active enzyme to substrate showed significant effect on the tensile strength compared to the samples without F XIIIa, however, color deterioration of the product was observed when adding F XIIIa.     

The effect of linseed and psyllium fibre on the gelling properties of unwashed mince from farmed meagre (Argyrosomus regius)

The gelling properties of farmed meagre (Argyrosomus regius) mince mixed with linseed and/or psyllium fibres (up to 4.0%, w/w) were studied. The effects of chilled storage time (15 days vs. 1 day) and cold gelling (setting at 2 ± 2 °C) were measured. Linseed addition increased ω3 PUFA content and worsened the gel products' texture. Psyllium functional fibre addition had only a negative effect upon breaking force and deformation, not affecting the remaining textural properties and improving water‐holding capacity (WHC) from 61–77 to 70–85%. The incorporation of 4.0% (w/w) psyllium seems to be advisable. Quality of heat‐induced meagre gels was unaffected by chilled storage time. Production of an acceptable cold set gel is feasible provided that enough time is allowed for completion of the setting process. Overall results showed a potential for combining small‐sized meagre (<2 kg) and psyllium fibres to produce high added‐value functional foods.