INVESTIGATIONS ON NITROSAMINE REDUCTION IN BONELESS HAMS PROCESSED IN ELASTIC RUBBER NETTINGS

N-Nitrosamines have been found in a wide variety of rubber-containing products. Since many types of boneless hams are processed in elastic nettings made with rubber, the potential exists for forming nitrosamines. In this paper we report that addition of excess nitrite to outer surface ham and netting samples results in a significant increase in N-nitrosodibenzylamine (NDBzA). Hams were then prepared with 100 ppm ingoing NaNO₂ and compared to a standard cure of 200 ppm NaNO₂. A highly significant reduction (p <0.01) in NDBzA (31 %) was noted in those made with the lower level of nitrite. In another series of experiments, hams were stored at either −2.2C or 2.2C, for up to six or 12 weeks, with the nettings on or off the ham. The overall results suggest that the level of NDBzA increased with netting contact time. Therefore it is advisable to remove the nettings after processing.     

Further Studies on the Formation of Nitrosamines in Cured Pork Products Packaged in Elastic Rubber Nettings

Traces of N-nitrosodi-n-butylamine (NDBA) and N-nitrosodiethylamine (NDEA) can form in cured pork products packaged in elastic rubber nettings due to the interaction of nitrite in meat and amines in the rubber. Studies were carried out to determine whether taking nettings off immediately after processing or placing a layer of collagen as a barrier between nettings and meat could prevent or minimize formation of the above nitrosamines. None was effective. However, cured pork products packaged in a reformulated rubber netting, made with different amine additives, contained either none or only negligible levels of NDBA or NDEA, but, instead, contained 8–104 ppb levels of a new nitrosamine, N-nitrosodibenzylamine which is reported to be noncarcinogenic.     

Identification of extractable substances from rubber nettings used to package meat products

Ten meat nettings were sampled from four different suppliers in the Netherlands. These meat nettings consisted both of natural rubber and of vegetable fibres. Nitrosamines were extractable up to 2 mg kg -1 netting, the nitrosamine being N -nitrosodibenzylamine. The nitrosatable substances found were precursors of N -nitrosodimethylamine and N -nitrosodibenzylamine and were extracted up to 0.4 mg kg -1 nettings. Considering the ratio of meat netting and foodstuff, the extractable amount of nitrosamines and nitrosatable substances does not raise concern for public health. The meat nettings were also screened for other potential migrants. Extractable amounts of several alkanes, alkenes, acids, antioxidants, plasticizers and sterols were found. Several of these extracted substances are not allowed in the Netherlands, although some are authorized in other countries. Several substances, however, have not been evaluated for use in food-contact materials and therefore the possible risk to public health is unknown.     

Benzo(a)pyrene contents of meat products

The Benzo(a)pyrene contents of 386 smoked and 18 grilled meat products were determined by application of capillary gas-chromatography-mass fragmentography using inner standards. 82 per cent of 183 black smoked hams contained appreciably more than the legal maximum amount of 1 ppb. The quantities of BaP increased very much with increase of soot accumulation on the surface. Only 15 per cent of 95 hams and only 9 per cent of 87 sausages smoked by normal methods had excessive BaP content. The amounts in excess of 1 ppb were much lower in these hams. Bratwurst grilled by use of pine-cones, spruce-cones and hard wood contained on average 28 ppb BaP. The BaP amounts of Bratwurst grilled over charcoal were without exception lower than 1 ppb.     

N-Nitrosodibutylamine and other Volatile Nitrosamines in Cured Meat Packaged in Rubber Nettings

Results from investigations of N-nitroso-n-dibutylamine (NDBA) in cured meat are compared from investigations in Denmark, the USA and Canada. NDBA was detected in very few samples and in quantities that were very low. Cured meats packaged in plastic wrappings or cotton nettings did not contain any NDBA. All cured meat packaged in elastic rubber nettings on the Danish market cannot contain more than 0.5 ppb NDBA.     

Benz(a)pyren in Fleischerzeugnissen

Zusammenfassung Im Rahmen der Lebensmittelüberwachung wurden 386 geräucherte und 18 gegrillte Fleischerzeugnisse auf ihre Gehalte an Benz(a)pyren untersucht. Die Bestimmungen erfolgten massenfragmentographisch mit einer Capillar-GC-MS-Kombination unter Verwendung innerer Standards.Von 183 schwarzgeräucherten Schinken enthielten 82% z. T. erheblich mehr als die zulässige Höchstmenge von 1 g BaP/kg. Die Mengen an BaP erhöhten sich dabei stark mit zunehmender äußerer Berußung.Bei 95 normal geräucherten Schinken wiesen nur 15% und bei 87 normal geräucherten Würsten nur 9% überhöhte BaP-Gehalte auf. Die Überschreitungen waren dabei von wesentlich geringerer Natur.Mit Kiefern- und Fichtenzapfen sowie mit Hartholz gegrillte Rostbratwürste enthielten durchschnittlich 28 g BaP/kg. Bei mit Holzkohle gegrillten Erzeugnissen lagen die BaP-Gehalte dagegen ausnahmslos unter 1 g/kg.

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Benzo(a)pyrene contents of meat products

Summary The Benzo(a)pyrene contents of 386 smoked and 18 grilled meat products were determined by application of capillary gas-chromatography-mass fragmentography using inner standards.82 per cent of 183 black smoked hams contained appreciably more than the legal maximum amount of 1 ppb. The quantities of BaP increased very much with increase of soot accumulation on the surface.Only 15 per cent of 95 hams and only 9 per cent of 87 sausages smoked by normal methods had excessive BaP content. The amounts in excess of 1 ppb were much lower in these hams.Bratwurst grilled by use of pine-cones, spruce-cones and hard wood contained on average 28 ppb BaP. The BaP amounts of Bratwurst grilled over charcoal were without exception lower than 1 ppb.

     

NITROSAMINES IN ALCOHOLIC BEVERAGES

A limited survey was carried out to determine the nitrosamine content of several varieties of alcoholic beverages (beer and ale, whiskey, wine, cider, etc.) sold in Canada. Of 22 samples of different beers and ales analyzed all but one contained traces of dimethylnitrosamine; the overall mean level found was 1.5 ppb. Only one Canadian rye and one Scotch whiskey out of a total of 13 samples contained traces of either dimethylnitrosamine or diethylnitrosamine. All the 8 wines and 7 cider samples were negative.     

Mutagenicity of N-nitroso compounds in Chilean ham and sausages

Chilean hams and sausages were analysed for the presence of nitrosodimethylamine and nitrosodiethylamine by GLC/NPD. The presence of 3.5–210ppb levels were found in 51.6% of the samples. All of the positive samples contained nitrosodimethylamine while only 11% of them contained nitrosodiethylamine. Mutagenicity assays were performed in Salmonella typhimurium . Strains TA 98 and TA 100 were used in absence and presence of S9 mix. A dose-response curve of the mutagenic activity was observed in TA 100 with S9 mix. Unscheduled DNA synthesis assay also confirmed that the purified extracts of hams and sausages at doses as low as 1 ppb are inducers of damage to DNA of human foetal lung cells.     

Sensory and Texture Quality of Dry-Cured Ham as Affected by Endogenous Cathepsin B Activity and Muscle Composition

Hams were processed with standard cure adjuncts under two drying temperatures and analyzed after aging for 7 mo. Dried hams revealed that flavor and texture traits were affected by moisture and nonprotein nitrogen (NPN) content and that NPN was enhanced by greater cathepsin B activity, lower salt levels and higher temperature. Two major defects of dry-cured ham, mushy mouthfeel and surface white film, occurred in about 15% of samples. Most of these hams had abnormal NPN values and were shown to originate from meat with high enzyme activity and low protein content. We concluded that this type of meat is prone to uncontrolled proteolysis and related undesired traits, and to be a potential hazard in dry-cured hams cured with less salt.     

Evaluating the profile of myofibrillar proteins and its relationship with tenderness among five styles of dry-cured hams

In order to investigate the relationship between profile of myofibrillar proteins and tenderness among 2 kinds of Chinese hams (Jinhua and Xuanwei) and 3 kinds of European hams (Iberian, Serrano and Parma), shear force, myofibril fragmentation index (MFI), SDS-PAGE, carbonyls content and Raman spectroscopy were investigated. The shear force and salt content of Chinese hams were significantly higher than that of European hams, while moisture content was lower than that of European hams (p < 0.05). MFI values and SDS-PAGE profile revealed that the degradation of myofibrillar proteins in Chinese hams was lower than in European hams. In addition, Chinese hams showed significantly higher carbonyls content and β-sheet content compared with European hams, indicated that proteins aggregation intensively inhibited the degradation of myofibrillar proteins in Chinese hams. These results indicated that the higher shear force in Chinese style hams could be attributed to the lower moisture content and limited proteolysis.     

Staphylococcus aureus survival, staphylococcal enterotoxin production and shelf stability of country-cured hams manufactured under different processing procedures

Fresh hams were inoculated with Staphylococcus aureus, cured, equalized, cold smoked or non-smoked, and aged. Initial S. aureus populations of 8.57 and 8.12 Log(10) CFU/cm(2) for salt and salt+NO(2)hams decreased to below the levels of detection after the fourth month of aging. S. aureus was detected following enrichment for 75% of the inoculated and 62% of the control hams at the end of the aging period. Staphylococcal enterotoxin was detected in 40% of the inoculated and 50% of the control hams following the aging period. The NaCl content of these hams with or without nitrite were 4.45/3.37% and a(w) values 0.94/0.91. Country-cured ham products obtained from retail stores in Kentucky were all negative for S. aureus enterotoxin. These results indicate that higher salt content and lower a(w) values on country-cured hams play an important role in controlling the growth and toxin production of S. aureus.     

Influence of pre-cure freezing of Iberian ham on proteolytic changes throughout the ripening process

This work aimed to investigate the effect of pre-cure freezing Iberian hams on proteolysis phenomena throughout the ripening process. Non-protein nitrogen (NPN), peptide nitrogen (PN) and amino acid nitrogen (AN) as well as amino acid and dipeptide evolution followed the same trend in both refrigerated (R) and pre-cure frozen (F) Iberian hams during processing. At the different stages of ripening, there were no differences in the content of NPN and AN while F dry-cured hams had higher levels of PN than R hams at the final step. This seemed to be more related to the salt content (lower in F than in R hams) than to the pre-cure freezing treatment. Most amino acids and dipeptides detected showed higher concentrations in F than in R Iberian hams at the green stage, being rather similar at the intermediate phases. At the final stage, the effects of pre-cure freezing of Iberian hams were not well defined, higher levels of some amino acids and dipeptides were found in R than in F Iberian hams whereas other amino acids were lower in R than in F hams.     

Use of nets treated with food grade coatings on controlling mold growth and mite infestation in dry-cured ham aging facilities

Dry-cured hams are frequently infested by mold and Tyrophagus putrescentiae in the aging facility during the 3 mo to 2-year aging period. Food grade coatings and these coating treated nets have been developed to control mold and mite growth on dry-cured hams to curtail the use of methyl bromide. Ham nets treated with food-grade coating of 1% propylene glycol alginate + 1% carrageenan + 40% propylene glycol were tested in a commercial research trial in 3 lots with approximately 100 hams in each lot, which also had approximately 100 control hams (untreated). Six of these hams were sent back to the research team. Three of these hams (already aged for 8 mo) were kept in a mite-infested simulated aging room for further evaluation of mold occurrence and mite population growth for another 6 mo. The other 3 hams from each lot of each treatment were tested by gas chromatography for propylene glycol residual. Mold evaluation indicated that the treatment hams reduced mold occurrence compared to the control hams, and there were no mite activities in any of these hams per inspection. In the mite-infested aging room, these coating-treated nets reduced mold and mite growth on whole hams (8–14-month-old). There was no difference in propylene glycol concentration between the control (0.072%) and net treated samples (0.053%). This concentration is 4 times less than 2%, the maximum acceptable concentration of this GRAS compound based on CFR 21,184.1666. Therefore, these hams met the legal requirements for commerce and were safe for human consumption and can be used to mitigate and help control mite infestations and mold growth of hams that are aged longer than 5 months.     

Effect of prefreezing hams on endogenous enzyme activity during the processing of Iberian dry-cured hams

The use of frozen/thawed raw material in the processing of Iberian dry-cured ham has been studied to determine its effect on the sensory quality of the final product. The proteolysis and lipolysis processes were measured by the proteolytic and lipolytic enzyme activities and free amino acids and free fatty acids. The thawed Iberian hams had lower salt contents throughout the process. The use of thawing raw material did not affect the proteolytic enzymes, cathepsins, aminopeptidases and dipeptidylpeptidases, only the activity of dipeptidylpeptidase III was reduced due to thawing. Moreover, there were no differences in the content of free amino acids between fresh and thawed hams during the whole process. However, the use of thawing hams affected the lipolytic activity. The activity of phospholipase and neutral lipase were significantly higher in the thawed hams and also the content of free fatty acids, at all the stages analyzed. Consumer sensory analysis showed thawed Iberian hams had the lowest hardness, probably due to an intense proteolysis. The acceptability of the Iberian hams was similar between fresh and thawed hams.     

Investigations of Edible Oils for Volatile Nitrosamines

Twenty-one commercial edible oils and five margarine samples were purchased locally and analyzed for nitrosamines (NAs) by a gas-liquid chromatograph interfaced with a Thermal Energy Analyzer. N-nitrosodimethylamine (NDMA), at levels of 0.22–1.01 ppb, was the only volatile apparent NA detected. These levels were found in 7/7 corn, 6/6 olive, 2/2 sunflower, 1/3 soybean, 2/3 undesignated oils, and 4/5 margarine samples. The other three oils and one margarine sample showed no NDMA at the lower limit of 0.1 ppb. These levels of nitrosamine detected in the edible oils tested were much lower than the levels previously reported.     

云南5种火腿水分分布与质构特性研究

目的 探究云南5种火腿水分分布与质构特性的差异及相关性。方法 以一年陈的宣威火腿、诺邓火腿、撒坝火腿、三川火腿和鹤庆火腿为原料,利用低场核磁共振（Low-field NMR,LF-NMR）与质地剖面分析（Texture profile analysis,TPA）分别测定不同地区火腿的水分分布与质构特性。结果 撒坝火腿的不易流动水和自由水横向弛豫时间（T2）分别为26.29 ms与151.13 ms,均显著高于其他4种火腿（P<0.05）,5种火腿的不易流动水单位质量信号量（A22）均高于结合水（A21）和自由水（A23）,其中撒坝火腿的A22为8857.97,显著高于其他4种火腿（P<0.05）;宣威火腿的硬度、咀嚼性和内聚性在5种火腿中最高,而弹性和回复性在5种火腿中最低;相关性分析显示,5种火腿的不易流动水含量与回复性、弹性呈极显著正相关（P<0.01）,与硬度呈显著负相关（P<0.05）,与咀嚼性、内聚性呈极显著负相关（P<0.01）,自由水含量与弹性、回复性呈极显著正相关（P<0.01）,而结合水含量与质构指标无显著相关性。结论 本研究表明不易流动水在5种火腿中占主要优势,其在5种火腿中的含量变化导致了火腿之间的质构特性差异,可以为火腿的品质调控提供理论依据。     

N-nitrosamines formation from secondary amines by nitrogen fixation on the surface of activated carbon

Our previous study demonstrated that many commercial activated carbon (AC) particles may catalyze transformation of secondary amines to yield trace levels of N-nitrosamines under ambient aerobic conditions. Because of the widespread usage of AC materials in numerous analytical and environmental applications, it is imperative to understand the reaction mechanism responsible for formation of nitrosamine on the surface of ACs to minimize their occurrence in water treatment systems and during analytical methods employing ACs. The study results show that the AC-catalyzed nitrosamine formation requires both atmospheric oxygen and nitrogen. AC's surface reactive sites react with molecular oxygen to form reactive oxygen species (ROS), which facilitate fixation of molecular nitrogen on the carbon surfaces to generate reactive nitrogen species (RNS) likely nitrous oxide and hydroxylamine that can react with adsorbed amines to form nitrosamines. AC's properties play a crucial role as more nitrosamine formation is associated with carbon surfaces with higher surface area, more surface defects, reduced surface properties, higher O(2) uptake capacity, and higher carbonyl group content. This study is a first of its kind on the nitrosamine formation mechanism involving nitrogen fixation on AC surfaces, and the information will be useful for minimization of nitrosamines in AC-based processes.     

盘县火腿深度腐败的微生物及挥发性风味化合物表征

为建立有效的干腌火腿腐败预测机制，比较正常与腐败盘县火腿的理化特性，并应用高通量测序和固相微萃取-气相色谱-质谱联用技术揭示正常和腐败盘县火腿的微生物群落结构和挥发性风味化合物。结果表明，腐败火腿的理化特征在于较低的NaCl含量和较高的pH值、水分活度（aw）和水分含量。肠杆菌科（Enterobacteriaceae）微生物是造成盘县火腿腐败的优势菌群，包括norank_Enterobacteriaceae、unclassified_Enterobacteriaceae和沙雷氏菌属（Serratia）。冗余分析表明，水分含量和pH值可能是影响两种未知肠杆菌科细菌的重要因素，而沙雷氏菌属与NaCl含量密切相关。腐败火腿比正常火腿具有更高水平的酮类、烃类、含苯和含硫化合物。LEFSe分析将苯酚、苯乙醛、1-十五烯、二甲基二硫醚和3-甲基丁酸鉴定为腐败火腿的主体特征风味。微生物与风味之间的网络分析显示norank_Enterobacteriaceae和unclassified_Enterobacteriaceae是腐败火腿挥发性风味的主要贡献者。本实验结果可以为盘县火腿的品质控制提供一定理论依据。     

Effect of pH(24), NaCl content and proteolysis index on the relationship between water content and texture parameters in biceps femoris and semimembranosus muscles in dry-cured ham

The aim of the present study was to determine the effect of pH level and NaCl content on the relationship between water content and texture parameters in semimembranosus and biceps femoris muscles in dry-cured ham. The experiment was undertaken using 18 hams, selected in a commercial slaughterhouse. Half of the hams had a pH<5.7 and the rest a pH>6.2, measured in the semimembranosus muscle at 24-h post mortem (pH(SM24)). The hams were treated with 20, 50 or 80g of NaCl per kg of ham. At the end of the aging process nine samples from semimembranosus and biceps femoris muscles were dried to different levels of water content covering the range from 22.4% to 58.5%. At the end of the drying period, a Texture Profile Analysis was used to determine textural parameters. Samples from biceps femoris muscle and samples from hams with low pH(SM24) showed a higher proteolysis index (100×non-protein nitrogen/total nitrogen) than samples from semimembranosus muscle and samples from hams with high pH(SM24), respectively. The proteolysis index decreased when the added NaCl amount increased. The proteolysis index was the parameter that best explained the modifications in the relationship between water content and the texture parameters (hardness, cohesiveness and springiness) of dry-cured ham muscles and it would be considered in order to predict the texture in dry-cured ham at different drying levels. Dry-cured hams with a lower proteolysis index were more prone to present harder texture at low water contents, which is typical of hams with crustiness problems.     

THE INFLUENCE OF GLUCONO DELTA LACTONE ON CURED HAM COLOR AND COLOR STABILITY

SUMMARY– Pairs of hams from 72 crossbred barrows slaughtered at three weight intervals (68.2, 90.9, and 113.6 kg) were assigned to three treatments of glucono delta lactone (GDL) (0, 30, or 60 g/l) and two post cure aging periods (1 or 14 days). Following post cure aging, samples from the boneless hams were exposed to light (200 ft-c) for various time intervals (0, 30, 60, 90, 120, 150, 180, and 1440 min) and nitric oxide- and total-pigments extracted with acetone/water and acetone/acid respectively. There were no significant differences in color formation or color stability of hams aged 1 or 14 days. The influence of GDL on nitric oxide- and total-pigment formation and stability was nonsignificant at most exposure intervals. Chemical analysis showed a significant decrease in moisture content of hams with increasing amounts of GDL added. Fat, chloride, and ash levels were not different for the three GDL treatments. Residual nitrite levels were found to be significantly lower for the 30 g/l of GDL in hams extracted one day post cure.