Potential for acrylamide formation in potatoes: data from the 2003 harvest

Reducing sugars, free amino acids, and the potential for acrylamide formation were determined in more than 50 potato samples from the 2003 harvest in Switzerland. The reducing sugar content strongly correlated with acrylamide, whereas no correlation was found between acrylamide and free asparagine or the pool of free amino acids. The reducing sugar contents and the acrylamide potentials were higher in most of the cultivars tested than in the samples from 2002. This was probably due to the hot and dry summer of 2003. Monitoring sugars and amino acids during heating at 120 °C and 180 °C showed that glucose and fructose reacted much faster than sucrose and the amino acids. Glutamine was consumed to a larger extent than any of the other amino acids. During prolonged storage, the reducing sugars decreased considerably while only moderate changes in the free amino acids were observed. Altogether, glucose and fructose remain the critical factors for acrylamide formation in potatoes and represent the most feasible way of reducing the formation of acrylamide in potato products.     

Effect of drying time,bean depth and temperature on free amino acid,peptide‐N,sugar and pyrazine concentrations of Malaysian cocoa beans

The effect of drying time on free amino acid, peptide‐N, sugar and pyrazine concentrations as well as the influence of bean depth and temperature on these compounds during cocoa drying was studied. Drying time, bean depth and temperature significantly decreased the concentration of free amino acids, peptide‐N, total reducing sugars and sucrose and increased the concentration of trimethyl‐, tetramethylpyrazine and total pyrazines in cocoa beans. The best drying treatment was obtained at the combination of bean depth/drying temperature of 8.3 cm/40 °C. This was based on the fact that it produced significantly high concentrations of hydrophobic free amino acids, peptide‐N and total reducing sugars and significantly low concentration of trimethyl‐, tetramethylpyrazine and total pyrazines. Drying treatment of 1.5 cm/60 °C significantly produced the lowest concentration of free amino acids, peptide‐N and total reducing sugars and the highest concentration of pyrazines. © 1999 Society of Chemical Industry     

Effect of salting and roasting on the carbohydrates and proteins of Iranian pistachio kernels

The free sugars which make up 2.7% of Iranian pistachio cv Badami were identified as fructose, glucose, sucrose, maltose, isomaltose, cellobiose, raffinose and stachyose. Both protein and free amino acids contained the same seventeen amino acids but lacked tryptophan, asparagine and glutamine. After salting and roasting, total available carbohydrates, total starches and dextrins, and total free sugars all decreased compared to controls, as did a number of individual sugars, especially the reducing sugars. While free amino acids had severely decreased, total protein amino acids and individual protein amino acid were not affected at all. The decreases in reducing sugars and in free amino acids may be due in part to their taking part in Maillard reactions.     

Role of amino acids and glucose in development of burnt off-flavours in liver sausage during heat processing

The effect of amino acids and glucose on the development of burnt off-flavours was investigated in meat model systems for liver sausage. At a constant glucose concentration, the burnt flavour was intensified by addition of an amino acid mixture. In a batter without liver, the development of burnt off-flavours, similar to those in liver sausage, could be induced through addition of exogenous amino acids and glucose. The endogenous amino acids from liver reacted more intensely than the exogenous amino acids in the formation of the burnt flavour components. After heating batches with added exogenous amino acids and glucose the free amino acid contents (73–89% of initial content) were higher than in batches to which liver was added (42–53% of initial content). The differences in the free amino acid content of glycine, glutamic acid and threonine were linearly related to the intensity of burnt flavour. Results indicate that burnt flavour is due to the Maillard reaction.     

Color Development in a Model System During Frying: Role of Individual Amino Acids and Sugars

The color of fried potato products is limited by reducing sugars, but can be affected by free amino acids. Filter paper discs saturated with solutions of amino acids in combination with glucose, fructose and sucrose were fried in oil to investigate color formation. Four phases of color development were identified; equilibrium, lag, rapid and slow phase, corresponding to the water content of the system. Lysine, 7-aminobutyric acid and glycine produced most color and glutamic acid least. Fry color of glucose and fructose systems was very similar, but sucrose systems produced less color. Glucose and fructose systems were not affected by pH changes, but there was a slight effect on sucrose systems.     

Antioxidative Maillard Reaction Products from Reducing Sugars and Free Amino Acids in Cooked Ground Pork Patties

Fifteen preformed Maillard reaction products (MRP) were prepared by refluxing 0.2M of three individual reducing sugars (glucose, xylose, and dihydroxyacetone) with 0.2M of five free amino acids (arginine, histidine, leucine, lysine, and tryptophan). MRP were added (3% v/w basis) to fresh ground pork patties prior to cooking and cooked to internal temperature 68°C and stored ai 4°C for 10 days. Samples were analyzed for TBA value on dav 0. 5. and 10. MRP were effective inhibitors of lipid oxidation in groind‘pdrk patties. The most effective were xyloselysine, xylose-tryptophan, dihydroxyacetone-histidine, and dihydroxy-acetone-tryptophan when compared to controls. A significant interaction (P < 0.001) existed between reducing sugars and amino acids.     

氨基酸对葡萄糖-天冬酰胺模拟体系中丙烯酰胺形成的抑制作用研究

研究4种氨基酸对已建立的葡萄糖-天冬酰胺模拟体系中丙烯酰胺生成的影响。方法 以葡萄糖-天冬酰胺组为对照组, 在此基础上分别加入半胱氨酸、甘氨酸、赖氨酸和谷氨酸4种氨基酸为实验组, 于140 ℃反应5~30 min, 测定反应后模拟体系的褐变程度、色差值、生成丙烯酰胺含量和剩余葡萄糖含量。 结果 4种氨基酸中, 半胱氨酸和谷氨酸对模拟体系中的褐变度和色差值的抑制作用较好; 半胱氨酸和赖氨酸对底物葡萄糖的消耗作用较快; 半胱氨酸对丙烯酰胺的抑制效果最好, 抑制率为(76.00±0.73)%, 其他氨基酸的抑制率分别为甘氨酸(38.39±0.44)%、赖氨酸(51.03±3.09)%和谷氨酸(28.76±2.43)%; 进一步研究发现, 当添加4.2 mmol半胱氨酸时, 丙烯酰胺抑制率达(95.32±0.47)%。结论 4种氨基酸相比, 半胱氨酸对丙烯酰胺形成的抑制效果最好, 且对于降低葡萄糖-天冬酰胺模拟体系的褐变度、色差值、葡萄糖含量有较好的效果。     

不同处理方式对芡实中游离氨基酸和碳水化合物的含量及淀粉消化率的影响

以芡实为原料,采用水煮后冷冻干燥、水煮后热风干燥、冷冻干燥、太阳晒干、热风干燥等5种方式处理芡实,测定处理后芡实中游离氨基酸、还原糖、总糖、淀粉含量及淀粉消化率,比较不同处理方法的差异性。结果表明:热风干燥、冷冻干燥、太阳晒干对芡实中还原糖、总糖和游离氨基酸的含量影响差异极显著(P<0.01),且冷冻干燥、太阳晒干、热风干燥的芡实中还原糖、总糖、游离氨基酸的含量依次下降,这表明真空冷冻干燥处理能最大程度地保留样品中还原糖、总糖等物质。冷冻干燥、热风干燥及太阳晒干的处理方法对赖氨酸、亮氨酸、色氨酸等游离氨基酸的含量影响差异不显著(P>0.05)。水煮加工处理显著影响芡实中还原糖、总糖和游离氨基酸的含量(P<0.01),而对淀粉含量影响差异不显著(P>0.05)。淀粉体外消化率分析表明,各样品的淀粉体外消化率均随着消化时间的增加而呈现上升的趋势,不同干燥方式显著影响芡实中淀粉的体外消化率,冷冻干燥、热风干燥、太阳晒干的芡实中淀粉体外消化率依次增大,水煮后样品中淀粉的体外消化率增加,且水煮后冷冻干燥的样品中淀粉的体外消化率最高。     

Liposome encapsulation protects bacteriocin-like substance P34 against inhibition by Maillard reaction products

Bacteriocins are biopreservatives with potential to be used in heat processed foods, and liposome encapsulation may offer a protective effect against interaction of these peptides with food compounds. In this work, Maillard reaction products (MRPs) were prepared by heating (90 °C for 7 h) different combinations of sugars and amino acids, and their inhibitory capacity against free and liposome-encapsulated bacteriocin-like substance (BLS) P34 was evaluated. MRPs formed by fructose and glycine had the highest inhibitory capacity against free and encapsulated BLS P43, remaining 50% of initial activity. Liposome encapsulation increased stability of BLS P34 when it was confronted to glucose/glycine, galactose/glycine, sucrose/glycine and glucose/alanine MRPs. Inhibition mostly occurs within the first 24 h of incubation of BLS P34 and MRPs. Inhibitory activity seems to be associated to melanoidin formation and antioxidant capacity of MRPs. The results show that liposome encapsulation of BLS P34 may be an interesting technique to increase the stability of antimicrobial peptides in heat treated foods.     

Effectiveness of an ultrafiltration device for use with the enzyme‐hydrolysed protein method for determining endogenous ileal nitrogen and amino acid excretion in the pig

The aim of the work was to perform an in vitro study to determine the effectiveness of Centriprep‐10 concentrator devices for use with the enzyme‐hydrolysed protein method for the determination of endogenous ileal nitrogen and amino acid flows. Different amounts of enzyme‐hydrolysed casein (EHC) were added to tubes containing digesta collected from pigs that had received a protein‐free diet for 5–8 days. The samples were centrifuged and then ultrafiltered using Centriprep‐10 concentrators. The precipitate from the centrifugation step was added to the retentate from the ultrafiltration, and this material was analysed for nitrogen and amino acids. The ultrafiltrates were also analysed for nitrogen. The amount of nitrogen that was deemed to have originated from the EHC and remained in the precipitate plus retentate fraction of digesta after processing, expressed as a percentage of the total amount of nitrogen added to the tubes as EHC, ranged from 1.0 to 5.0%. The overall mean amounts of amino acid in the precipitate plus retentate fractions originating from the EHC, expressed as a percentage of the amino acids added to the tubes as EHC, ranged from 2.4 to 5.8%. The results demonstrate that with Centriprep‐10 concentrators there is a less than complete separation of nitrogen and amino acids originating from EHC from endogenous material in digesta, but for most amino acids this is unlikely to be due to binding of the amino acids to digesta. The incomplete separation of EHC from the endogenous fraction of digesta by Centriprep‐10 concentrators may lead to a small overestimation (approximately 2%) of endogenous ileal nitrogen and amino acid flows. © 2001 Society of Chemical Industry     

Comparison of volatile Maillard reaction products from tagatose and other reducing sugars with amino acids

In this study, in order to investigate the effects of tagatose on the Maillard reaction, volatile Maillard reaction products (V-MRPs) produced from aqueous model systems containing various reducing sugars (glucose, galactose, fructose, and tagatose) and amino acids (glycine, valine, leucine, asparagine, and cysteine) were analyzed and then compared. Furans, furan derivatives, pyrazines, and some sulfur-containing heterocyclic compounds, such as thiazoles, thiophenes, and thiols, were mainly identified. The amounts of furans and furan derivatives were higher in the model systems of ketoses (fructose or tagatose) with amino acids than those of aldoses (glucose or galactose) with amino acids. In particular, 2-acetylfuran was detected 2-20 times more in the V-MRPs of tagatose as compared to those produced from the other reducing sugars. Also, 2-acetylpyrrole, one of nitrogen-containing heterocyclic compounds, was more abundant from the thermal reactions of tagatose-glycine and tagatose-valine compared to those of other reducing sugars-amino acids. More 2-acetylthiazole and thiophenes were found in tagatose-cysteine model system than in those of glucose with cysteine.     

Effect of mass and turning time on free amino acid,peptide-N,sugar and pyrazine concentration during cocoa fermentation

A response surface methodology (RSM) was used to determine the optimum condition for mass and turning time during cocoa fermentation. Mass and turning time were used as independent variables; concentrations of free amino acids, peptide-N, sugars and pyrazines were the dependent variables. The R² values for peptide-N, tetramethylpyrazine and total pyrazines were greater than 0·9. Both lower (10 kg) and higher (100 kg) cocoa mass together with lower (0 min) and higher (10 min) turning time gave products containing low concentrations of hydrophobic, total and other free amino acids, peptide-N, fructose, glucose and total reducing sugars; in contrast, those of acidic free amino acids gave higher concentrations. Trimethyl-, tetramethyl- and total pyrazines increased significantly (P<0·05) at higher mass (100 kg) and higher turning time (10 min). From the highest concentration of the important flavour precursors ie hydrophobic free amino acids, total reducing sugars and peptide-N, the recommended mass of cocoa beans and turning time for an optimum cocoa fermentation condition was 60 kg and 5 min, respectively. © 1998 Society of Chemical Industry.     

不同烹饪方式的羊肚菌在体外消化过程中营养成分溶出差异比较

为研究不同烹饪方式对羊肚菌营养品质的影响,采用体外消化方法对煮制、蒸制以及烤制处理的不同粒度羊肚菌粉（粗粉、超微粉）进行消化。比较了消化后的羊肚菌粉显微形态,模拟胃、肠消化液中还原糖、蛋白质、游离氨基酸、总酚含量以及DPPH（1,1-Diphenryl-2-Picrylhydrazyl）自由基清除能力、铁离子还原能力（Ferric Ion Reducing Antioxidantpower,FRAP）、阳离子自由基清除能力2-azinobis-（3-ethylbenzthiazoline-6-sulfphonate,ABTS）。结果表明：经过体外胃、肠消化后,烤制处理的羊肚菌粉还原糖、蛋白质、多酚溶出量最高,蒸制其次,煮制最低,烤制比煮制平均依次高62.87%、58.58%、4.69倍;蒸制处理的羊肚菌,溶出的游离氨基酸含量在所有处理中最高,粗粉、细粉平均为40.40 mg/g,分别比烤制、蒸制高出18.77%,19.81%。超微粉碎不能有效提高还原糖、多酚的溶出,但可以显著提高蛋白质、游离氨基酸的溶出（P<0.05）;模拟消化液的DPPH值没有显著差异,但FRAP和ABTS值差异显著（P<0.05）,烤制处理的最高,其次是蒸制,煮制最低;超微粉碎不能有效提升羊肚菌模拟消化液的抗氧化水平。该研究为羊肚菌的科学食用提供了参考。     

反应型可可香料的氨基酸和还原糖的Plackett-Burman设计筛选

本研究采用Plackett-Burman试验设计,选取缬氨酸、甘氨酸、苯丙氨酸、亮氨酸、酪氨酸、苏氨酸、丝氨酸、谷氨酸、精氨酸、葡萄糖、果糖11个可能的可可风味相关因子进行筛选。统计分析结果表明:苯丙氨酸、丝氨酸、亮氨酸、谷氨酸、精氨酸、甘氨酸对美拉德反应的可可风味产物中的几种重要的致香成分具有最显著的影响。未发现葡萄糖和果糖对可可风味有任何差异贡献。选择这5种氨基酸和两种还原糖制备反应型可可香料,产物进行感官分析,并用GC-MS分析其中的致香成分和含量,鉴定出52种成分。     

外源糖对普洱茶品质的影响(Ⅰ)

研究添加外源糖(葡萄糖为0.2%～1%,果糖、半乳糖、甘露糖和木糖分别为0.6%,0.8%)处理普洱生茶(50℃,处理3 d)后普洱茶品质相关的各内含成分(水浸出物,茶多酚,儿茶素,游离氨基酸,咖啡碱,可溶性糖,TR,TF,TB)的含量变化。结果表明添加外源单糖可显著改变普洱茶的各内含成分含量。果糖能显著降低咖啡碱含量,木糖次之。     

Effects of different types of soy sauce on the formation of heterocyclic amines in roasted chicken

The objective of the study was to determine the effect of different types of soy sauce and marinating time on the formation of heterocyclic amines (HCAs) in roasted chicken. Chicken breast samples were marinated with sweet, salty, light and dark soy sauce at 0, 3, 6 and 12 h (control treatment was the chicken without marinade). The concentrations of free amino acids, sugars and creatinine were determined before roasting while HCA concentrations were determined after roasting. All types of soy sauce significantly increased (p ≤ 0.05) the concentration of HCAs in roasted chicken with increasing marinating time. The highest increment of total concentration of HCAs was found in samples marinated with light soy sauce (887%) followed by dark (375%), salty (193%) and sweet (169%) at 12 h. PhIP (2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine) showed a substantial reduction in samples only momentarily marinated with sweet, salty and dark soy sauce (0 h). Free amino acids were found to be more strongly correlated with the formation of HCAs than reducing sugars or creatinine.     

Dietary fat and ruminally protected amino acids for high producing dairy cows

Eight early lactation Holstein cows, used in a replicated 4 x 4 Latin square design, were fed the following diets: control; control plus ruminally protected amino acids (15 g methionine and 20 g lysine); control plus added fat (.32 kg 60:40 animal and vegetable blend and .36 kg of Ca salts of fatty acids); control plus ruminally protected amino acids plus added fat. The objective was to examine the effect of ruminally protected forms of lysine and methionine and dietary fat on milk yield and composition. Cows were fed for ad libitum consumption of total mixed diets consisting of 50% forage and 50% concentrate on a DM basis. Added fat increased milk, fat, and 4% FCM yield but decreased milk protein percentage. Ruminally protected amino acids increased milk protein percentage. The combined effect of fat and ruminally protected acids increased milk fat percentage and yield more than the sole addition of either supplement. Added fat increased the percentage and yield of long-chain fatty acids in milk. Plasma free fatty acids were also increased by fat addition. Adding ruminally protected amino acids to fat-supplemented diets may help alleviate the milk protein depression found with added fat.     

Effects of benzylaminopurine on mango fruit ripening

The total and reducing sugars, organic acid and free amino acid contents of the edible portions of mango (cv. Boribo) were determined in unripe and ripe fruits, both treated and untreated with benzylaminopurine (BA).Total and reducing sugar contents were increased and organic acids and free amino acid contents were decreased after ripening in both cases. Benzylaminopurine delayed ripening and the composition of the ripe fruit was different from that of the untreated control.     

Postharvest changes in physicochemical characteristics and free amino acids content of immature vegetable soya bean (Glycine max L.) grains

The aim of this study was to investigate the changes in physicochemical characteristics and free amino acid profile occurring in immature vegetable soya bbean during postharvest storage under three temperatures [5, 10 and 20 (control), ±1 °C] for 7 days. The results showed that a lower temperature provided an effective control in reducing weight loss, maintained firmness, delayed changes in the pod colour and soluble sugars concentration. Twenty‐two free amino acids in immature soya beans also identified by the ¹H NMR spectroscopy were strongly affected by postharvest temperature, and there were time‐specific differences in the concentration. Those significant differences in free amino acids concentration among storage conditions were closely associated with aspartate and glutamate degradation. Additionally, after 7‐day storage at 5 and 10 °C, the soya bean grains accumulated the highest amount of some essential and flavour amino acids, which revealed storage conditions selected should be dictated by the goal.     

不同氨基酸和糖对美拉德反应产物的影响

利用半胱氨酸、甘氨酸、谷氨酸3 种氨基酸和木糖、葡萄糖2 种还原糖作为反应底物,模拟美拉德反应制备香精,并对其香气成分和有害物质进行综合分析。结果表明：参与反应的氨基酸种类越多,所测得的挥发性物质种数也越多,反应产物的风味越丰富;甘氨酸参与的美拉德反应中丙烯酰胺的生成量较少,而谷氨酸的参与反应中丙烯酰胺的生成量较多;还原糖种类对丙烯酰胺的产生影响不大;谷氨酸参与的美拉德反应产物中,5-羟甲基糠醛（5-hydroxymethylfurfural,5-HMF）含量高,而半胱氨酸和甘氨酸参与的反应产物中,5-HMF的含量较低;木糖可减少产物中的5-HMF的含量。利用本实验条件制备香精,产物中的丙烯酰胺和5-HMF含量在安全范围内。