Formation of Heterocyclic Amines in a Meat Juice Model System

Bovine meat juice was used as a model system to examine the kinetics of the formation of heterocyclic amines. The formation was examined at temperatures between 100 and 225°C for 0.5-180 min. Heated samples were subjected to solid-phase extraction and HPLC analysis. IQx, MeIQx, 7,8-DiMeIQx, 4,8-DiMeIQx, PhIP, harman and norharman were identified. The formation of the IQx derivatives and PhIP followed a first-order model C_t=B(1–e^k1(t1-t0), and the temperature dependence followed the Eyring equation k=k_bT/he^ΔS/Re-^ΔH/RT. The parameters in the first-order model and the Eyring equation could be estimated from our data. The degradation of heterocyclic amines at high temperatures was analyzed and the products were found to be less mutagenic.     

Kinetics of Formation of Polar Heterocyclic Amines in a Meat Model System

A model system was used to examine kinetics of formation of polar heterocyclic amines by heating the precursors creatinine, glucose and amino acids in proportions similar to those in bovine meat but at higher concentrations. Formation of heterocyclic amines was studied between 150 and 225°C for 0.5–120 min, depending on temperature. Heated samples were subjected to solid phase extraction and HPLC analysis, with photodiode array detection for identification and quantification of heterocyclic amines. IQx, MeIQx, 7,8-DiMeIQx, 4,8-DiMeIQx, PhIP, harman and norharman were identified. A first-order reaction model and the Eyring equation were fitted to the formation of polar heterocyclic amines to obtain rate constants and their temperature dependence.     

Formation of heterocyclic amines in slices of Longissimus thoracis beef muscle subjected to jets of superheated steam

The kinetics of the formation of heterocyclic amines (HA) were measured on slices of Longissimus thoracis (LT) muscle subjected to impinging jets of superheated steam. Product temperature was either 170 or 200 °C and treatment duration ranged from 1 to 20 min. The concentrations of IQx, MeIQx, 4,8-DiMeIQx and PhIP followed regular kinetic patterns. HA formation increased significantly between 170 and 200 °C. The quantities of IQx and 4,8-DiMeIQx formed in LT slices were 3 to 4-fold smaller than those formed in meat juices, while quantities of MeIQx and PhIP remained comparable. A first-order kinetic model taken from the literature was adapted to describe the results taking into account product temperature variations over the course of the experiment.     

FORMATION OF HETEROCYCLIC AMINES IN MEAT EMULSION EXTENDED WITH SOY PROTEIN

Formation of heterocyclic amines (HAs) during heating of meat emulsions at selected temperatures was studied to determine the influence of soy protein and fat contents on yields of HAs. Meat emulsion with two different fat contents, 6% (low) and 19% (high), and with two soy protein contents, 0% (none) and 10%, were used in the study. The emulsions were heated at temperatures of 180 and 200C for times varying from 0 to 40 min. HAs namely IQx (2-amino-3-methylimidazo[4,5-f]quinoxaline), MelQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline), and PhIP (2-amino-1-methy-6-phenylimidazo[4,5-b]pyridine) were identified and quantified in the meat emulsions. Concentrations of IQx were from 0 to 8.26 ng/g of emulsion; MeIQx concentrations were from 0 to 14.73 ng/g and PhIP concentrations were from 0 to 2.48 ng/g. Yields of the HAs depended on temperature, time, soy protein and fat contents. Formation of the HAs in the meat emulsions after an initial lag period followed first order kinetics. Increasing soy protein content decreased the maximum concentrations of IQx and MeIQx formed at the different heating condition.     

大蒜硫化物对油炸鸡胸肉中MeIQx的抑制机制

为探究二烯丙基二硫（diallyl disulfide,DAD）和二丙基二硫（diphenyl disulfide,DPD）对油炸鸡胸肉中2-氨基-3,8-二甲基咪唑并[4,5-f]喹喔啉（2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline,MeIQx）形成的影响和抑制机制,本实验对添加DAD和DPD的无油和含油鸡胸肉及模拟体系中MeIQx、羰基价、MeIQx的中间体及前体变化进行分析。结果表明：油炸鸡胸肉中MeIQx含量较焙烤鸡胸肉中MeIQx含量显著提高（从10.9 ng/g增加至56.4 ng/g）,DAD和DPD对MeIQx的抑制率明显提高,从无抑制分别提高至57.4%（DAD）和67.1%（DPD）,并在模拟体系中得到验证。DAD和DPD的添加显著减缓体系中羰基价的上升速率和前体的消耗速率。添加DAD可降低甲醛的形成量,DPD则对3 种MeIQx中间体的形成均有显著的抑制作用（P＜0.05）。可推测大蒜硫化物可能是通过减少油脂氧化所产生的羰基,从而减弱其对MeIQx前体经Strecker降解产生中间体的催化作用,实现抑制MeIQx的形成。     

Profiles and concentrations of heterocyclic aromatic amines formed in beef during various heat treatments depend on the time of ripening and muscle type

Heterocyclic Aromatic Amine (HAA) profiles and concentrations depended on several factors. The largest changes in the HAA profile were observed in meat ripened (chill stored) for 5-10days. Amines whos concentration varied most prominently included: Phe-P 1, harmane, AαC, IQ, IQx, PhIP, MeAαC, and MeIQx. HAA concentrations were strongly correlated with concentrations of the above compounds. Time of storage significantly affected the HAA profile and concentration. The profile changed dynamically for storage times up to 10days. For longer times the profile stabilized, only the HAA content increased. A novel, highly precise and accurate HAA analytical method was developed for this study. Results may help to optimize meat processing technology from the point of view of reducing concentration of HAA formed during heat treatment, including the most carcinogenic; IQ, IQx, MeIQx and PhIP amines.     

Profiles and concentrations of heterocyclic aromatic amines formed in beef during various heat treatments depend on the time of ripening and muscle type

Heterocyclic Aromatic Amine (HAA) profiles and concentrations depended on several factors. The largest changes in the HAA profile were observed in meat ripened (chill stored) for 5–10 days. Amines whos concentration varied most prominently included: Phe-P 1, harmane, AαC, IQ, IQx, PhIP, MeAαC, and MeIQx. HAA concentrations were strongly correlated with concentrations of the above compounds. Time of storage significantly affected the HAA profile and concentration. The profile changed dynamically for storage times up to 10 days. For longer times the profile stabilized, only the HAA content increased.A novel, highly precise and accurate HAA analytical method was developed for this study. Results may help to optimize meat processing technology from the point of view of reducing concentration of HAA formed during heat treatment, including the most carcinogenic; IQ, IQx, MeIQx and PhIP amines.     

一种检测杂环胺类化合物的酶联免疫检测方法的建立

为了制备一种广谱性杂环胺抗体,并建立一种可以实现多种杂环胺同时检测的快速分析方法。以杂环胺2-氨基-3,4-二甲基咪唑[4,5-f]喹喔啉(MeIQx)为原料,将其与丁二酸单甲酯酰氯(MCO)反应合成杂环胺半抗原,通过活化酯法将半抗原与蛋白偶联制备免疫原进一步制备多克隆抗体,最终建立间接竞争酶联免疫分析方法(ic-ELISA)。该方法灵敏度(IC₅₀,以MeIQx计)为81.16 μg/L,检测限(IC₁₅)为12.07 μg/L。方法对喹啉类杂环胺(IQ、MeIQ)、喹喔啉类杂环胺(IQx、MeIQx、4,8-DiMeIQx、7,8-DiMeIQx、4,7,8-TriMeIQx)以及吡啶类杂环胺(PhIP)具有相同的识别能力,交叉反应率均达到93%以上。油炸牛肉和肉松样品中杂环胺(MeIQx)添加回收率在91.18%~98.64%之间,检测结果与液相色谱串联质谱法(LC-MS/MS)有很好的一致性(R2=0.9927)。本文建立的酶联免疫分析方法可以实现喹啉类、喹喔啉类以及吡啶类杂环胺总量的检测,为热加工肉制品中杂环胺的检测提供了一种简单、准确的快速检测方法。     

Pectin-Protein Interaction in Tomato Products

The pH influenced the viscosity of a model system of tomato product which consisted of citrus pectin and bovine serum albumin. The viscosity change was completely reversible depending on the pH. The same pH effect was observed in tomato products. Since the amino acid compositions of proteins suggest that the electrostatic property of water-soluble protein fraction from tomato juice can be similar to that of bovine serum albumin, the comparison of pH effects indicates that pectin-protein interaction may be involved in consistency of tomato products. Denaturation of protein may result in a decrease in the serum viscosity during processing.     

Kinetics of Heterocyclic Amines Formation in Meat Emulsion at Different Fat Contents

The objectives of the study were to investigate the yield of heterocyclic amines (HA) in meat emulsion during heating as in cooking at different temperatures using the kinetic modeling approach and to determine the influence of fat content on the formation of HAs. Meat emulsion with two different fat contents namely extra lean (6 g/100 g) and regular (19 g/100 g) were used in the study. The samples were heated at 160, 180 and 200°C for times, varying from 5 to 40 mins. HAs namely IQx, MeIQx, and PhIP were identified and quantified using the HPLC. Formation of HAs was dependent on temperature, time, and fat content. It followed the first-order kinetics. Increasing fat content of samples resulted in lower HAs concentrations and lower activation energy of reaction. Fat enhanced formation of HAs in meat but apparently diluted available precursors for reactions.     

Potential of synchronous fluorescence spectroscopy coupled with chemometrics to determine the heterocyclic aromatic amines in grilled meat

In this study, the potential of synchronous front-face fluorescence spectroscopy (SFS) coupled with chemometrics was investigated for the determination of heterocyclic aromatic amines (HAA) in cooked meat samples. Bovine meat samples (1–2 mm thick, 5 cm diameter) taken from Longissimus thoracis muscle were cooked at an average temperature of 237 °C for 5, 7 and 10 min. Four HAA (4, 8-DiMeIQx, MeIQx, IQx and PhIP) were determined on the cooked meat samples using classical LC-APCI-MS/MS method. In parallel, SFS spectra were recorded using a spectrofluorimeter on the same cooked meat samples in an excitation wavelength range of 250–550 nm using offsets of 20, 30, 40, …, 160 nm between excitation and emission monochromators. The three-dimensional synchronous fluorescence data set was analyzed using PARAFAC (parallel factor) analysis and N-PLS (n-way partial least square) regression method. PARAFAC analysis allowed capturing the fluorescence changes occurring in meat during cooking: the best model was obtained with 2 components (core consistency of 100% and explained variance of 99.2%). Whereas the loading profile of component 1 showed a maximum excitation at about 495 nm and an optimal offset of 60 nm, the loading profile of component 2 was characterized by a maximum excitation at 367 nm and an optimal offset of 90 nm. The results obtained using N-PLS regression showed good correlation between the spectral and analytical data: average recovery of 104% for 4, 8-DiMelQx, 102% for both MelQx and IQx, and 103% for PhIP were obtained. In conclusion this study indicates that SFS along with chemometrics has the potential to be used as a rapid and non-destructive technique for the determination of HAA contents in meat.     

Formation of heterocyclic amines in a model system during heating

The formation of heterocyclic amines (HAs) in a model system during heating at 100, 150, or 200 degrees C for varied lengths of time was studied. The following systems were used: (i) phenylalanine, (ii) creatinine, (iii) phenylalanine and glucose, (iv) phenylalanine and creatinine, (v) glucose and creatinine, and (vi) phenylalanine, glucose, and creatinine. Results showed that HAs could only be found in both systems of glucose and creatinine, and of phenylalanine, glucose, and creatinine. Both 2-amino-9H-pyrido-[2,3-b]indole (AalphaC) and 2-amino-3-methyl-9H-pyrido-[2,3-b]indole (MeAalphaC) were observed in the former system, and the formation rate of AalphaC was higher than MeAalphaC. For the latter system, 2-amino-3-dimethylimidazo[4,5-f]quinoxaline (IQx), 9H-pyrido-[4,3-b]indole (Norharman), 1-methyl-9H-pyrido-[4,3-b]indole (Harman), AalphaC, and MeAalphaC were present. The formation rate of AalphaC was the highest at 200 degrees C, followed by MeAalphaC, Harman, Norharman, and IQx. In addition, the varieties of HAs increased both with increasing heating time and temperature. The amounts of HAs formed were less in the model system of glucose and creatinine than that of phenylalanine, glucose, and creatinine. The same trend was also observed for the formation rate of HAs. At 150 or 200 degrees C, the amounts of IQx, Harman, Norharman, AalphaC, and MeAalphaC increased in the initial period of heating and then reached a plateau. The results of this study provided a basic understanding of the conditions that result in the formation of HAs during cooking of meat and fish products.     

ANTIOXIDANT PROFILES OF CORBARA SMALL TOMATOES DURING RIPENING AND EFFECTS OF AQUEOUS EXTRACTS ON J774 CELL ANTIOXIDANT ENZYMES

The influence of ripening on the antioxidant profile of Corbara small tomatoes was studied in fruit at five different ripening stages. An increase in the content of both carotenoids and flavonoids was observed during ripening. At the "deep red"stage (StIV) fruit had an average carotenoid content 58% higher than that of the "ripe"stage (StIII) which is the usual harvest time for markets. Carotenoid concentrations parallel the value of lipophilic amioxidant activity while the aqueous/methanol antioxidant activity was not correlated with total flavonoid content. The effect of antioxidants extracted from stage IV tomato was assayed on an oxidative-stressed culture of macrophages by measuring the activity of the antioxidant enzymes. An aqueous extract containing the pool of hydrophilic antioxidants was prepared. The antioxidant effects of this pool were compared with the same effect produced by a mixture of standard compounds constituted by the main tomato hydrophilic antioxidants. Results demonstrate that the efficacy of Corbarino aqueous extract on this cell system is higher than that of reconstituted mixture .     

Effect of green tea extract and microwave pre-cooking on the formation of heterocyclic aromatic amines in fried chicken meat products

Heterocyclic aromatic amines (HAAs) are mutagenic compounds formed naturally in meats after thermal processing and are classified as a probable human carcinogen. Also, mutagenic potency of HAAs is about 100-fold stronger than that of aflatoxin and 2000-fold stronger than that of benzo[a]pyrene. The aims of the present study were to investigate HAA contents and to determine HAA existence in coated chicken drumsticks (CDs) and coated chicken wings (CWs) which are frequently consumed in fast food chains after purchasing from fast food restaurants, and the effects of green tea extract added into the cover material and microwave-precooking for the mitigation and the formation of HAAs in CD and CW samples produced using a laboratory model. HAA (IQx, IQ, MeIQx, MeIQ, 7,8-DiMeIQx, 4,8-DiMeIQx, PhIP, AαC, MeAαC) analysis was done by HPLC after solid-phase extraction. MeIQx is the dominant HAA in all CD and CW samples obtained from fast food restaurants, and its level was found to vary between 0.22–33.73 and 11.22–62.83 ng/g, respectively. PhIP was detected in 5 out of 20 samples from fast food restaurants with a maximum level of 3.15 ng/g, and IQx, 7,8-DiMeIQx, AαC, and MeIQ were also detected. MeIQx values of CW and CD samples produced with the laboratory model varied between not detected and 1.45 and not detected and 2.32 ng/g, respectively, while IQ, MeIQ, 7.8 DiMeIQx, 4,8-DiMeIQx, AαC, and MeAαC were not detected in any of the CW or CD samples produced using the laboratory model. HAA contents of CD and CW samples obtained from fast food restaurants were higher than those of samples produced using the laboratory model due to the possible effect of uncontrolled frying conditions in restaurants. In addition, it was determined that the addition of green tea extract (GTE) and microwave pre-cooking (MC) did not present any detectable effect on reducing the formation of HAAs in fried CDs and CWs produced using a laboratory model under controlled frying conditions.     

Microstructure and bioaccessibility of different carotenoid species as affected by high pressure homogenisation: A case study on differently coloured tomatoes

The effect of high pressure homogenisation (HPH) on structure (Bostwick consistency, particle size distribution and microstructure) and carotenoid in vitro bioaccessibility of different tomato pulps was investigated. HPH decreased tomato particle size due to matrix disruption and increased product consistency, probably due to the formation of a fibre network. Homogenisation also resulted in a decrease of in vitro bioaccessibility of lycopene, ζ-carotene, and lutein. Such decrease was attributed to the structuring effect of HPH. An inverse relation between tomato consistency and carotenoid in vitro bioaccessibility was found. This dependency was affected by carotenoid species and its localisation within the matrix. It could be observed that one matrix (e.g. (homogenised) red tomato pulp) can contain carotenoids with a very low bioaccessibility (lycopene) as well as carotenoids with a very high bioaccessibility (lutein), indicating that carotenoid bioaccessibility is not solely dependent on the matrix.     

Modelling the formation of heterocyclic amines in slices of longissimus thoracis and semimembranosus beef muscles subjected to jets of hot air

The formation of heterocyclic amines (HAs) was modelled in slices of longissimus thoracis (LT) and semimembranosus (SM) beef muscles subjected to jets of hot air at temperatures ranging from 170 and 250 °C and treatment times ranging from 1 to 20 min. The quantity of HAs formed in the SM muscle was clearly less that that formed in the LT muscle as soon as the heat treatment was longer than 300 s. The extreme dehydration obtained with the hot-air jets slowed the formation of IQx, MeIQx and, particularly, 4,8-DiMeIQx compared with superheated steam treatments. The reverse effect was observed for PhIP concentrations which increased 1.4- to 5.5-fold. This highlights the important effect of water activity variations on HA formation, even at very low a_w values.     

Concentration Effect on Odor Addition or Synergism in Mixtures of Methyl Sulfide and Tomato Juice

SUMMARY: The effect of various concentrations of tomato juice and methyl sulfide (Me₂S) in triple distilled water on threshold values of the juice-Me₂S mixtures was studied on juices prepared from five varieties of canning tomatoes. When Me₂S and tomato juice were diluted to less than 10 ppb and 1,000 ppm respectively, before mixing, no significant interaction between juice and Me₂S was observed in the juice-Me₂S mixture. The odor intensities of the two components (as measured by threshold values in distilled water) were additive at subthreshold concentrations. As the concentrations of juice and Me₂S were increased before mixing, an increasing degree of interaction or synergism was observed in the mixture. At concentrations of 10⁵ ppm juice and 1 ppm Me₂S odor intensity of the mixture was approximately double that which would be expected on an additive basis. However, this may not be a case of true synergism if the concentrations which give rise to the effect produce other products of lower threshold values.     

红酵母类胡萝卜素发酵助剂的筛选及应用

研究了几种促进剂和前体对红酵母RY－98类胡萝卜素发酵的影响，从中选出了番茄汁、花生油和核黄素3种对红酵母生长及类胡萝卜素合成具有显著促进作用的发酵助剂，并确定了适宜的用量。应用试验和发酵过程动态分析表明，这3种发酵助剂增产效果明显。当同时添加番茄汁3mL/L、花生油1.2mL/L和核黄素3.5mg/L时，菌体量、类胡萝卜素质量分数和产量可分别比对照组提高39.4%、32.8%和85.1%，且对发酵过程菌体生长及生理代谢规律无不良影响。     

Proteolytic activity of molds and their metabiotic association with Salmonella in a model system

The aim of this study was to investigate the proteolytic ability of some strains of aspergilli, fusaria, and penicillia and the metabiotic effect of Fusarium oxysporum and Penicillium expansum on Salmonella. The proteolytic activity of the target molds was determined on tomato juice agar and tomato juice, whereas the metabiotic effect of F. oxysporum and P. expansum on Salmonella was assessed in a model system consisting of tryptone soy broth with different amounts of tomato juice added. Fusaria, some aspergilli, and one strain of penicillium showed a proteolytic activity on tomato juice agar. In addition, Salmonella survival was enhanced in tryptone soy broth plus 20 or 50% tomato juice in the model system previously inoculated with F. oxysporum.     

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.