Model System Studies on N-Nitrosamine Formation in Cured Meats: The Effect of Slice Thickness

A model bacon system has been developed which enables a more reproducible determination of N-nitrosamines when compared to conventional methods of bacon production. Utilizing this system, the effect of slice thickness and frying time on nitrosopyrrolidine (NPyr) formation has been demonstrated. Short frying periods (3 min/side) result in higher NPyr levels for thinner sliced samples and longer frying periods (5 min/side) result in higher NPyr levels for thicker sliced samples. The level of N-nitrosamine formed is integrally related to slice thickness and frying time and may be explained when two factors are considered, the rate of N-nitrosamine formation and the rate of its volatilization.     

EFFECTS OF LIQUID SMOKE ON LIPID OXIDATION IN A BEEF MODEL SYSTEM AND RESTRUCTURED ROASTS

Commercially available liquid smokes were added to a meat model system and to a restructured beef product to assess their ability to suppress lipid oxidation. Aqueous hickory smoke was the most effective smoke in suppressing oxidation as reflected in 2-thiobarbituric acid reactive substances (TBARS) of microsomal lipids. Phenol was not antioxidative in the model system. Addition of liquid smoke had no significant effect on "stale, cardboardy, painty" flavor or aroma of restructured beef roast slices stored at 4C. The aroma and flavor of sliced beef deteriorated over the 7-day storage regardless of liquid smoke addition. Hexanal in the control roasts increased during storage from ∼0 to >3 ppm; those containing aqueous liquid smoke contained little (< 0.5 ppm) hexanal. Smokes, but not the phenol mix, kept TBARS near day zero (0.2 mg/kg) levels through 7 days.     

COLOR AND TEXTURE DEVELOPMENT OF POTATO CYLINDERS WITH LIQUID SMOKE DURING BAKING, FRYING AND MICROWAVING

The rate of color and texture development in partially fried before freezing potato cylinders processed by deep fat frying, microwaving and baking was determined. The effect of 0, 1, 3 or 5% wt/wt solution containing 30% liquid smoke was measured at intervals during thermal processing and the reaction order and rate determined. Also, five different wood and dextrose‐derived browning agents were compared at 1% wt/wt addition. The processing method had a significant effect on the reaction rates of color and texture development during processing. Microwaving was faster than frying, which was faster than baking. The addition of liquid smoke led to a significant increase in the rate of color production but had no statistically significant effect on texture. The addition of 1% liquid smoke increased the reaction rate by adding carbonyls, which limit the reaction rate in potatoes. Higher levels of liquid smoke did not change the reaction rate because the carbonyls were no longer limiting the reaction. The processing method and the addition of the browning agent had no effect on the reaction order which remained a pseudo zero‐order reaction. Thus, liquid smoke could be used to reduce processing times, potentially saving money and decreasing acrylamide formation.     

Effects of N-nitrosopyrrolidine, nitrite and pyrrolidine on tumour development in mice as related to ingestion of cured meat

The incidence of tumours in mice fed a standard chow diet and given either N-nitrosopyrrolidine (NPyr), nitrite (NO₂) or nitrite plus pyrrolidine (NO₂ + Pyr) in the drinking water for 12 months at 100mg, 1 g and 1 g plus 100mg/litre, respectively, was compared with that for a control group (C) receiving no additives. Differences between groups in weight gain and feed consumption were not significant. Group 3 (NO₂) drank less water (P < 0·05) than those in groups 1 (C) and 2 (NPyr). Water intake of mice in group 4 (NO₂ + Pyr) did not differ from that of any of the other three groups. Survival rates were: 94% (C), 80% (NPyr), 92% (NO₂) and 83% (NO₂ + Pyr); but the differences were not statistically significant. Gross examination upon autopsy revealed that the incidence of all tumours in group 2 (NPyr) was 10- to 20-fold higher than that in any other group. Histological examination confirmed that NPyr induced more (P < 0.05) malignant tumours in liver and lungs with any other treatment; otherwise there were no significant differences. Results indicated that NO₂ + Pyr (nitrite plus a secondary amine) did not increase the frequency of carcinogenic tumours in mice.     

A survey of fish products for volatile N-nitrosamines

A study was undertaken to determine the levels of nitrate, nitrite and volatile N-nitrosamines of various fish products (halibut, salmon, cod, sole, ocean perch, scallops). The samples were analysed for five volatile nitrosamines, namely dimethyl-nitrosamine (DMN), diethylnitrosamine (DEN), dibutylnitrosamine (DBN), nitrosopyrrolidine (NPyr) and nitrosopiperidine (NPip), all of which are potent carcinogens. Both gas–liquid chromatographic (Coulson electrolytic conductivity detector, pyrolytic mode) and thin-layer chromatographic methods were used for estimating the levels of nitrosamines. The average level of nitrate was 8 part/10⁶ (range 0–94 parts/10⁶), and nitrite was present in traces only. Traces of DMN (3–12 parts/10⁹) were found in some uncooked (raw) fish. Increased levels of DMN (3–18 parts/10⁹) and traces of DEN (4–14 parts/10⁹) were observed after baking and frying, indicating formation of these compounds during cooking. None of the samples contained DBN, NPyr or NPip. In 10 out of 15 samples the identities and levels of DMN and DEN were confirmed by gas liquid chromatography–high resolution mass spectrometry.     

Determination of carcinogenic tobacco-specific nitrosamines in mainstream smoke from U.S.-brand and non-U.S.-brand cigarettes from 14 countries.

Tobacco-specific nitrosamines (TSNAs) comprise one of the major classes of carcinogenic compounds in mainstream cigarette smoke. As part of collaborative efforts between the World Health Organization and the U.S. Centers for Disease Control and Prevention (CDC) to reduce tobacco use and resulting disease, the CDC examined carcinogenic TSNA levels from cigarettes obtained from selected countries around the world. Using a modern, high-throughput liquid chromatography/mass spectrometry/mass spectrometry method under stringent quality control protocols, we determined the carcinogenic TSNA levels in mainstream smoke from a globally marketed brand, Marlboro, and from local top-selling cigarette brands from 14 countries. The levels of carcinogenic TSNAs in mainstream smoke collected using a 35-ml puff volume, 60-s puff interval, and 2-s puff duration correlated well (R=0.79, p<.0001) with previously reported levels in the corresponding tobacco filler. Marlboro cigarettes purchased in 10 countries had significantly higher carcinogenic TSNA levels in mainstream smoke than did local-brand cigarettes from the same country. In only one country, Brazil, were the carcinogenic TSNA levels in mainstream smoke from Marlboro cigarettes significantly lower than in the locally popular brand. However, carcinogenic TSNA levels in mainstream smoke from Brazilian Marlboro cigarettes were usually lower than those in mainstream smoke from the Marlboros purchased in the other 13 countries, suggesting a reason for the difference. The wide range of mainstream smoke carcinogenic TSNA levels measured in the present study (8.7-312 ng/cigarette) suggest that manufacturers can lower the carcinogenic TSNA levels and that, for similar filter ventilation, carcinogenic TSNA levels in the tobacco filler of a cigarette are a useful indicator of the corresponding levels in mainstream smoke.     

Effect of Liquid Smoke on the Growth of Lactic Acid Starter Cultures used to Manufacture Fermented Sausage

Fermented sausage was manufactured using a commercial lactic acid starter culture and varying levels of liquid smoke. Samples were taken during the 24 hr fermentation period and the lactic bacterial count, pH and titratable acidity determined. Final pH values, titratable acidity and lactic bacterial counts were not affected by recommended use levels of liquid smoke, although exponential growth was delayed. Growth studies in a broth medium containing liquid smoke suggest that liquid smoke has the potential for inhibiting the lactic starter cultures used to make fermented sausage.     

Characterization of new nitrosamines in drinking water using liquid chromatography tandem mass spectrometry

N-Nitrosodimethylamine (NDMA), a member of a group of probable human carcinogens, has been detected as a disinfection byproduct (DBP) in drinking water supplies in Canada and the United States. To comprehensively investigate the occurrence of possible nitrosamines in drinking water supplies, a liquid chromatography-tandem mass spectrometry technique was developed to detect both thermally stable and unstable nitrosamines. This technique consisted of solid-phase extraction (SPE), liquid chromatography (LC) separation, and tandem quadrupole linear ion trap mass spectrometry (MS/MS) detection. It enabled the determination of sub-ng/L levels of nine nitrosamines. Isotope-labeled N-nitrosodimethylamine-d6 (NDMA-d6) was used as the surrogate standard for determining recovery, and N-nitrosodi-n-propylamine-dl4 (NDPA-dl4) was used as the internal standard for quantification. The method detection limits were estimated to be 0.1-10.6 ng/L, and the average recoveries were 41-111% for the nine nitrosamines; of these, NDMA, N-nitrosopyrrolidine (NPyr), N-nitrosopiperidine (NPip), and N-nitrosodiphenylamine (NDPhA) were identified and quantified in drinking water samples collected from four locations within the same distribution system. In general, the concentrations of these four nitrosamines in this distribution system increased with increasing distance from the water treatment plant, indicating that the amount of formation was greater than the amount of decomposition within this time frame. The identification of NPip and NDPhA in drinking water systems and the distribution profiles of these nitrosamines have not been reported previously. These nitrosamines are toxic, and their presence as DBPs in drinking water may have toxicological relevance.     

Further studies on n-nitrosopyrrolidine and its precursors: Effects of ascorbic acid and vitamin E on tumor development in mice as related to consumption of cured meat

Two experiments were carried out to ascertain if supplementation of a semipurified diet to Swiss-ICR mice with either ascorbic acid (AA), vitamin E (Vit E) or a combination of the two would modulate the carcinogenic effects of N-nitrosopyrrolidine (NPyr) and of its probable precursors (nitrite-N0(2) and pyrrolidine-Pyr) in Experiment I or of NPyr in Experiment II. Results indicated that neither AA nor Vit E modulated the carcinogenic effects of NPyr or of its probable precursors (NO(2) and Pyr). Results verified a previous report from our laboratory showing that NPyr increased the number of malignant tumors by some 5-8 fold over controls. There was a lower incidence of tumors in the control group on the semi-purfied diet than in the groups given NO(2) and Pyr, although both treatments had a low frequency of malignant tumors (1 63 versus 5 72 survivors). Results support our earlier study suggesting that neither NO(2) nor Pyr alone or in combination together contribute to cancer-at least in the laboratory mouse.     

Inactivation of Listeria monocytogenes in raw and hot smoked trout fillets by high hydrostatic pressure processing combined with liquid smoke and freezing

High hydrostatic pressure (HHP; 200 MPa for 15 min), liquid smoke (0.50%, v/v) and freezing (−80 °C, overnight) was used to eliminate Listeria monocytogenes in BHI broth, raw and smoked trout. The bactericidal effect of liquid smoke solutions (L9 and G6), HHP and their combinations was evaluated against L. monocytogenes LO28, EGD-e and 10403S and further continued with the most resistant strain (10403S) to the combined treatment. For first time, a synergistic effect of liquid smoke and HHP was observed and was further enhanced by freezing prior to HHP. The effect of HHP and liquid smoke, prior to freezing was highest in BHI compared to raw and smoked trout. A major synergistic effect of HHP, liquid smoke and freezing was observed, reaching a 5.48 or 1.93 log CFU/g reduction when smoked or raw trout was used respectively. Furthermore, high injury levels occurred, among treatments reaching up to 55.98%.Industrial relevanceThis paper illustrates for first time, the possibility of using a very low pressure in combination with liquid smoke and freezing to eliminate L. monocytogenes. It was demonstrated that treatment of trout samples with liquid smoke followed by freezing prior to pressurization at 200 MPa for 15 min reduced the number of L. monocytogenes by more than 5-log CFU/g. Such a remarkable bacterial inactivation at a very low pressure (compared to common industrial practices) is a significant achievement that could allow production of safer and novel products by HHP at an affordable price, as the cost of equipment manufacture as well as the maintenance and running costs could be reduced substantially at lower operation pressures.     

Kinetics of Total Phenolic Content and Total Color Difference During Liquid Smoking of Kashar Cheese

Since the late 1800s, smoking has been used for giving color, taste, and aroma to foods, as well as for developing new products. Due to health, technical, and economic reasons, one of the widely used smoking techniques preferred by manufacturers is smoking with liquid smoke. In this study, fresh Kashar cheese slices were smoked by immersion in liquid smoke at concentrations (10, 20, 30%), smoking temperatures (20, 30, 40°C) and smoking times (30, 60, 120, 180, 300 s). The appropriate equation and kinetic parameters were determined for the variation of total phenolic content and total color difference. A pseudo-first-order kinetic model was obtained, and activation energy values were calculated as 10.7 kJ/mol and 24.3 kJ/mol, respectively.     

Effect of inhibitory liquid smoke fractions on Listeria monocytogenes during long-term storage of frankfurters

Listeria monocytogenes is a potential health hazard that sometimes finds harborage in facilities that manufacture ready-to-eat meats, including frankfurters. Our objectives were to examine the effect of select liquid smoke extracts on control of L. monocytogenes on frankfurters. Frankfurters were either obtained locally at retail (containing lactate-diacetate) or manufactured for us in-house or by a local processor (without added lactate-diacetate). In challenge studies of retail franks containing lactate-diacetate, low levels of L. monocytogenes were able to increase by 2 to 8 log on 5 of 10 brands tested when held at 1.6 degrees C (35 degrees F). Treatments with liquid smoke extracts were able to reduce and control growth of L. monocytogenes on the most permissive franks for 10 weeks when treated for as long as 90 s to as little as 5 s versus untreated controls. Effective control of L. monocytogenes was also obtained when dipped for as short as 1 s or when dropped through an atomized mist produced by a pressurized spray canister. Frankfurters manufactured without lactate-diacetate by a large commercial manufacturer of franks were sprayed with liquid smoke by using a commercial device as they exited the peeler. When inoculated at three different levels (10(1), 10(2), and 10(3) CFU) with a four-strain cocktail of L. monocytogenes and stored at 6 degrees C (43 degrees F), the smoke-treated samples again demonstrated effective control of L. monocytogenes relative to untreated control samples. Frankfurters produced in-house without lactate-diacetate and treated while still in the casing also showed suppression of Listeria compared with controls. The data show that surface application of liquid smoke extracts by dipping or spraying may inhibit the growth of L. monocytogenes on frankfurters during shelf life and should facilitate a claim as an alternative 2, and possibly alternative 1, process for (U.S. Food and Drug Administration) hazard analysis and critical control point purposes.     

Screening of commercial and pecan shell-extracted liquid smoke agents as natural antimicrobials against foodborne pathogens

Liquid smoke extracts have traditionally been used as flavoring agents, are known to possess antioxidant properties, and serve as natural alternatives to conventional antimicrobials. The antimicrobial efficacies of commercial liquid smoke samples may vary depending on their source and composition and the methods used to extract and concentrate the smoke. We investigated the MICs of eight commercial liquid smoke samples against Salmonella Enteritidis, Staphylococcus aureus, and Escherichia coli . The commercial liquid smoke samples purchased were supplied by the manufacturer as water-based or concentrated extracts of smoke from different wood sources. The MICs of the commercial smokes to inhibit the growth of foodborne pathogens ranged from 0.5 to 6.0% for E. coli, 0.5 to 8.0% for Salmonella, and 0.38 to 6% for S. aureus. The MIC for each liquid smoke sample was similar in its effect on both E. coli and Salmonella. Solvent-extracted antimicrobials prepared using pecan shells displayed significant differences between their inhibitory concentrations depending on the type of solvent used for extraction. The results indicated that the liquid smoke samples tested in this study could serve as effective natural antimicrobials and that their inhibitory effects depended more on the solvents used for extraction than the wood source.     

Kinetics of Potato Color and Texture Development during Baking, Frying, and Microwaving with the Addition of Liquid Smoke

ABSTRACT:  The rate of color and texture development in par-fried French fries coated with liquid smoke and thermally processed was determined. Liquid smoke containing 8% to 11% carbonyls was diluted to 30% and applied to 1 side of French fries at 0%, 1%, 3%, or 5% by weight. The fries were immersion fried at 190.6 °C for 4 min, microwaved (900 watts) for 4 min, or baked at 190.6 °C for 20 min. Color and texture measurements were recorded at intervals during processing. Liquid smoke increased the rate of browning in French fries. Browning followed pseudo zero-order kinetics, with the a value, Browning index, and total change in color (ΔE) showing the best fit. When liquid smoke was added in high concentrations the reaction rate did not increase as more liquid smoke was added because the carbonyls were no longer limiting the rate of Maillard browning. The rate of color development in French fries was also affected by the thermal processing method. Frying developed color at the fastest rate, followed by microwaving and baking. Although liquid smoke increased the rate of color development in French fries, it did not affect French fry texture. Through sensory testing, it was determined that liquid smoke can be used to improve the color of microwaveable French fries without affecting French fry flavor or texture.     

Chemical effects of smoke processing on frankfurter quality and palatability characteristics

Frankfurters were made by standard commercial practices except for the smoke treatment which involved four different methods: solid smoke-aerosol, liquid smoke-aerosol, liquid smoke-external dip and liquid smoke-internal mix. For control purposes, frankfurters were prepared without any smoke treatment. All frankfurters were packaged and stored at 5°C with samples removed for analyses weekly for three weeks. All smoke-processing treatments resulted in products assessed as overall acceptable with the experienced sensory panel unable to detect differences among the various methods of manufacture except for the franks made by mixing liquid smoke in the emulsion. However, the flavour scores of those products subjected to external smoke-processing treatments were higher and more acceptable than the other two treatments. Frankfurters manufactured using aerosol smoke treatments were rated by sensory panellists as the most tender. However, shear force measurements indicated that those franks processed with external liquid smoke treatments were somewhat less tender. Liquid smoke-processing techniques favoured the development of a more desirable cured colour. The most stable colour was attributed to the liquid smoke-processing system in which the smoke materials were mixed in the emulsion. All palatability properties (sensory and colour) were highly correlated with the smokiness of the product. Generally, storage time had little effect on frankfurter palatability characteristics.     

INHIBITION OF LISTERIA INNOCUA AND L. MONOCYTOGENES IN A LABORATORY MEDIUM AND COLD-SMOKED SALMON CONTAINING LIQUID SMOKE

Five commercial liquid smokes were tested in vitro and the most inhibitory to Listeria monocytogenes ATCC 19115 and L. innocua ATCC 33090 was Charsol Supreme. Chum salmon samples (100-g each) were brined, dipped for 15 s at varying concentrations of liquid smoke, inoculated with L. innocua, cold-processed and analyzed. Liquid smoke concentrations of 60–100% reduced L. innocua by 3-log₁₀/g in the final product. Dwell times of 15 s to 5 min using 60% liquid smoke gradually decreased Listeria survival with an optimum 5-min dip. Isoeugenol was antilisterial in vitro but lacked synergism with liquid smoke in cold-smoked salmon. An immunoassay kit detected low inoculum levels (< 100 CFU/g) of L. innocua in one of three samples that were treated with liquid smoke for two and four minutes. Charsol Supreme was antilisterial but could not be relied on to totally eliminate Listeria in cold-smoked salmon. Panelists found the 0 to 2-min dipped sockeye salmon slightly desirable with no significant (p < 0.05) differences. The 5-min treatment was significantly (p < 0.05) darker, scored lower in desirability and flavor and contained 93 ppm of phenolic compounds.     

Oxidative effects of cigarette smoke on the human skin

The oxidative effects of cigarette smoke on the human skin were investigated. A remarkable increase in the conversion ratio of squalene (SQ) to squalene monohydroperoxide (SQHPO) due to exposure to cigarette smoke was observed using a CL-HPLC (high performance liquid chromatography with a chemiluminescence detector) system. The results showed that cigarette smoke caused lipid peroxidation. We also found that the addition of chain-breaking-type antioxidants, such as oolong tea extract, inhibited the peroxidation. When cultured human skin fibroblasts were exposed to cigarette smoke, this increased the intensity of ultraweak chemiluminescence (CL), leading us to assume that cigarette smoke caused oxidation in cultured human skin fibroblasts. When the cultured human skin fibroblasts were treated with antioxidants such as glutathione, thiotaurine, hypotaurine and ascorbic acid there was little increase in CL, meaning that oxidation had been prevented in the human skin fibroblasts. We also exposed the human forearm to cigarette smoke and obtained sebum using cotton immersed in acetone in order to measure hydroperoxide levels by means of a CL-HPLC system. The exposure of skin to the smoke caused a dose-dependent increase in hydroperoxides derived from cigarette smoke. Further exposure of the forearm to cigarette smoke increased the intensity of CL, but pretreating the skin with antioxidants such as glutathione, thiotaurine and hypotaurine inhibited this increase. From these results, we concluded that cigarette smoke had an oxidative effect on SQ, cultured human skin fibroblasts and the surface of the human skin. The application of antioxidants prevented the cigarette smoke-induced oxidation. We consider that these oxidative effects on the skin could be a cause of skin disorders and skin aging.     

Study of several aspects of a general method for the determination of polycyclic aromatic hydrocarbons in liquid smoke flavourings by gas chromatography-mass spectrometry

The effectiveness of the steps of a general method, which includes alkaline treatment of the samples, extraction, clean-up and analysis, for the determination of polycyclic aromatic hydrocarbons in liquid smoke flavourings and smoked foods have been studied, by using mixtures of pure polycyclic aromatic hydrocarbons and of smoke flavouring compounds. All these products were applied to samples of liquid smoke flavourings in order to test the effectiveness of each step of the method, as well as to investigate its effect on real samples, and thus obtain a suitable procedure for the study of polycyclic aromatic hydrocarbons in liquid smoke flavourings. The alkaline treatment has been proved to be necessary because of its capability for removing some smoke components. Both cyclohexane and dichloromethane are able to extract polycyclic aromatic hydrocarbons with high recovery percentages; however, cyclohexane is more adequate due to its lower ability to extract other smoke flavourings components. It is important to note that the elution sequence of polycyclic aromatic hydrocarbons during the clean-up step is quite different depending on the solvent used to dissolve the extract, which determines the ability of this process to isolate polycyclic aromatic hydrocarbons for their accurate identification and quantification by gas chromatography-mass spectrometry in selected ion monitoring mode. Finally, the PAHs present in a liquid smoke flavouring and their concentrations were determined; it was observed that, despite the different extraction solvents and clean-up procedures used, the results were very similar.     

卷烟烟气小动物口鼻暴露方法的建立及评价

  背景和目的  国际经济合作与发展组织（OECD）测试导则（TG）对化学物质暴露环境参数和浓度稳定性有明确要求,本文的目的是建立符合其要求的卷烟烟气小动物口鼻暴露方法。  方法  在小动物口鼻暴露系统中测定4种卷烟烟气在不同稀释倍数下颗粒物数量浓度和挥发性有机物浓度,以确定符合OECD要求的卷烟烟气稀释倍数等参数。在该参数条件下,对40小鼠口鼻暴露连续2周,用酶联免疫吸附方法（ELISA）检测小鼠肺灌洗液白细胞介素-10（IL-10）、白细胞介素-6（IL-6）和肿瘤坏死因子-α（TNF-α）水平变化,以进一步评估方法的稳定性。  结果  （1）4种卷烟主流烟气颗粒物浓度和总挥发性有机物（TVOC）在大于100倍稀释时,时间和空间变异系数均小于10%,符合OECD的要求,低于100倍则变异较大。（2）IL-10变异系数在6.9%~8.6%之间,TNF-α变异系数在13.4%~17.6%;IL-6变异系数在16.8%~23.2%之间。  结论  所建立的卷烟烟气口鼻暴露方法符合OECD导则要求,生物学效应指标检测结果可靠稳定。      

滤棒中三醋酸甘油酯用量对卷烟主流烟气有害成分释放量的影响

为明确卷烟滤棒成型过程中增塑剂三醋酸甘油酯对烟气有害成分释放量的影响,制备了4种不同三醋酸甘油酯用量的醋酸纤维滤棒及相应的试验卷烟,并对其烟气常规化学指标、有害成分释放量和感官品质进行了分析评价.结果表明:①三醋酸甘油酯的用量在5.51％～13.31％的范围时,卷烟主流烟气中总粒相物、焦油、烟碱等常规指标变化不大;②除苯酚、间-对甲酚的释放量随着三醋酸甘油酯用量的增加逐渐降低外,一氧化碳(CO)、氢氰酸(HCN)、4-(甲基亚硝胺基)-1-(3-吡啶基)-1-丁酮(NNK)、氨(NH3)、苯并[a]芘(B[a]P)、巴豆醛、对苯二酚、间苯二酚、邻苯二酚、邻甲酚等成分的释放量或基本无变化,或变化不明显;③三醋酸甘油酯对卷烟感官质量的影响不明显.