Effects of phosphine and methyl bromide fumigation on the volatile flavor profile and sensory quality of dry cured ham

In separate experiments, randomized complete block designs with three replications were utilized to evaluate the effects of phosphine (PH₃) (0, 200 and 1000 ppm for 48 h) and methyl bromide (MB) (0, 4, 8, 16, and 32 mg/L for 48 h) fumigation concentration on the volatile flavor compound concentrations in dry cured ham. Minimal differences existed (P > 0.05) in the presence and concentration of aroma active compounds in both PH₃ and MB fumigated hams but sulfur and oxidation compounds were more prevalent (P < 0.05) in the fumigated treatments when compared to the control. As phosphine fumigation concentration increased, the residual concentration of phosphine also increased in the hams (P < 0.05), but all samples contained levels that are lower than the legal limit of phosphine allowed in stored food products (0.01 ppm) in the United States. A triangle test (n = 56) indicated that consumers could not discriminate (P > 0.75) between the control hams and those that were fumigated with PH₃. Minimal aroma/flavor differences existed among MB, PH3 and control hams, and dry cured ham that was fumigated with PH₃ was safe for consumption based on residual phosphine concentrations in the meat tissue.     

Effect of intensity of smoking treatment on the free amino acids and biogenic amines occurrence in dry cured ham

The aim of this study was to investigate the effect of the intensity of smoking treatment on the evolution of free amino acids (FAAs) of dry cured ham during processing. The correlation between FAAs and biogenic amines (BAs) content was also investigated as well as its effect on the perception of some sensory characteristics of ripened hams.     

Proteolysis,protein oxidation and protease activity in dry‐cured Xuanwei ham during the salting stages

Twenty‐four experimental dry‐cured Xuanwei hams were salted using a standard method for 90 days. The proteolysis, protein oxidation and protease activities in biceps femoris (BF) and semimembranoesus (SM) muscles of dry‐cured Xuanwei ham were investigated during the salting phase. At the end of salting, the salt content increased to 35.2 g kg^?1 muscle in BF and 54.2 g kg^?1 muscle in SM. During the salting stage, salt soluble proteins were degraded mainly into water soluble proteins that were further broken down to peptides with molecular weights mostly greater than 1 kDa. Although large amounts of smaller peptides and free amino acids were generated, especially when the hams were aged. The carbonyl contents were increased but lower than 1.57 nmol mg^?1 proteins in muscles during the salting stage. The cathepsin B, dipeptidyl peptidase I (DPP I), alanyl (AAP), arginyl (RAP) and leucyl (LAP) aminopeptidase all remained active while salt content strongly inhibited cathepsin L and DPP IV in the first 90 days. The results suggested that the salting process promoted the hydrolysis of proteins, and increased the muscle protein oxidation at a slower rate.     

Predicted gas loss of sulfuryl fluoride and methyl bromide during structural fumigation

Elimination of insects in grain-milling facilities requires the periodic use of a gaseous insecticide (fumigant) that can destroy pests. Ideally, the fumigant concentration within a treated building should remain constant during the fumigation process to enhance efficacy while minimizing the amount of fumigant required. However, fumigant is often slowly lost through cracks and crevices within the structure. Wind impact on this leakage loss and in natural ventilation is explored using computational fluid dynamics (CFD). Two surrogate enclosure geometries, based on actual commercial grain mills, are used in the analysis. Building materials are assumed impermeable to fumigants, and cracks within structures are approximated as square regions where permeability parameters can be specified (i.e., porous jumps). Half-loss times (HLT) for sulfuryl fluoride (SF) and methyl bromide (MB) within the structure can be simulated. When diffusion dominates (no wind), SF had increased leakage rates of ∼5.4% over MB. However, simulated HLT due to diffusion are in the order of years for both fumigants. If the wind is blowing at measurable rates, convection-driven losses dominate and leakage from the mill is independent of the fumigant being used. Predicted half-loss times for MB and SF are statistically indistinguishable for external wind velocities from 0.125to 8 m s^-1. Therefore, HLTs are insensitive to fumigant physicochemical properties when the wind is blowing. Representative and diverse wind-frequency analysis for California and Texas show limited intervals of calm wind periods, and median wind speeds at or above those investigated in this analysis. Thus, decisions for product use should be based on efficacy, cost, and environmental impact, since convective-induced leakage rates are similar.     

Evaluation and selection of yeasts isolated from dry-cured Iberian ham by their volatile compound production

One hundred and seventeen yeast strains isolated from dry-cured Iberian ham from the four different protected designations of origin of Spain were investigated for their volatile compound production. The yeast strains were grouped into the two main yeast species usually found in this product (Debaryomyces hansenii and Candida zeylanoides) and 10 different biotypes by restriction mitochondrial DNA analysis. Yeast strains were grown in a designed model culture medium under conditions representative of dry-cured ham processing. Volatile compounds were extracted from this medium using solid-phase micro-extraction and were analysed by gas chromatography/mass spectrometry. Marked differences in volatile compound production were found between D. hansenii and C. zeylanoides and between the mitochondrial DNA patterns of these species. Two of the mitochondrial DNA patterns of D. hansenii exhibited the highest production of the volatile compounds involved in the dry-cured flavour. Consequently, these patterns of D. hansenii should be proposed as starter cultures for dry-cured ham.     

Effects of halothane genotype and pre-slaughter treatment on pig meat quality. Part 2. Physico-chemical traits of cured-cooked ham and sensory traits of cured-cooked and dry-cured hams

Forty-eight castrated F₂ offspring of Piétrain and Large White pigs were allocated to a 3×2 factorial design in order to study the interactive effect of halothane genotype (NN, Nn and nn) and pre-slaughter treatment (referred to as ’Experimental’ (EXP) and ’Commercial-like’ (COL) conditions; the latter involving short transportation, mixing unfamiliar pigs and slaughtering shortly after transport) on the qualities of cured-cooked and dry-cured hams. At 24 h post mortem, the hams were collected and assigned to cured-cooked (right ham) and dry-cured (left ham) ham processing. A sample of M. semimembranosus (SM) was collected before cooked ham processing, was used for chemical composition analysis, cured and then cooked at various temperatures. Cooking losses and compression tests were carried out after cooking on these SM samples. The water and collagen content of SM muscle was significantly higher in nn pigs compared with the two other genotypes. At all cooking temperatures (60, 65 and 70 °C), SM muscles from nn pigs showed higher cooking losses and instrumentally assessed toughness than the other genotypes, the heterozygous pigs being intermediate. The technological yield of cured-cooked ham processing was lower in nn, compared with NN and Nn animals. Cooked hams from nn pigs were drier, tougher, stringier and less smooth than NN and Nn pigs. The heterozygous pigs were similar to normal pigs for all texture characteristics with the exception of toughness for which they got a significantly higher score than NN pigs. The pigs slaughtered under the COL conditions had a better slice cohesiveness and a significantly lower dryness, than pigs slaughtered under the EXP conditions. The effect of HAL genotype on slice cohesiveness was significant only when pigs were slaughtered under the EXP conditions. Dry-cured hams from nn pigs showed significantly more visual defects, but were less tough, smoother and more fondant (softer) than NN and Nn pigs. The dry-cured hams from pigs slaughtered under the COL conditions had a better cohesiveness between muscles and a more intense yellow colour of fat than those from pigs slaughtered under the EXP conditions. COL pigs were also judged significantly less tough, smoother and more fondant than EXP ones. Overall, the effects of pre-slaughter treatment were small compared with those of the HAL genotype. The effects of HAL genotype on the sensory traits of cured-cooked ham were similar to those reported for fresh meat. However, the good textural characteristics of dry-cured ham processed from HAL positive pigs are somewhat surprising and need to be confirmed.     

Effects of weather conditions on sulfuryl fluoride and methyl bromide leakage during structural fumigation in a flour mill

A validated Computational Fluid Dynamics (CFD) model of structural fumigation was used to perform 54 fumigation simulations (half with sulfuryl fluoride, SF, and half with methyl bromide, MB) using recorded hourly average weather data for 4 July and 1 September at Indianapolis International Airport for the years 1996-2006. These weather data were used as the simulation boundary conditions. Although the fumigations were simulated for the same time periods, the results indicated substantial variations in the fumigant leakage rates. The 11-year averages of wind speeds on 4 July and 1 September were 3.8 and 2.4 m/s, respectively, resulting in half-loss time (HLT) differences between the fumigations on the two days. On average, the HLT was 4 h lower on 4 July than on 1 September. When comparing the results between individual fumigations, substantial differences in the fumigant leakage were observed, regardless of the fumigant type and whether or not the fumigations were performed at the same time period. This implied that using past fumigation data as the primary means for evaluating the structural sealing quality of a current fumigation is not adequate. Predictions of fumigant leakage rate and fumigation performance should incorporate quantifiable sealing effectiveness and weather information for the planned fumigation period. Comparisons between SF and MB fumigations indicated that under exactly the same weather conditions and fumigation practices the leakage characteristics of SF and MB do not differ. In practical situations where the dosage requirements for SF and MB are typically not the same, however, the leakage rates of SF and MB fumigations could be different due to the buoyancy effect. Nevertheless, the magnitude of the difference may or may not be significant depending on other factors such as sealing quality, wind speed and direction, and ambient temperature. The effects of these factors should be further quantified.     

Determination of volatile compounds and quality parameters of traditional Istrian dry-cured ham

The aim of this work was to determine the characteristics of Istrian dry-cured ham by instrumental methods and sensory analysis. The aroma-active compounds of Istrian dry-cured ham from 2010 and 2012 were investigated by using headspace-solid phase microextraction (SPME) and gas chromatography–mass spectrometry (GC–MS). Samples of biceps femoris were also evaluated by measuring physical and chemical characteristics. 92 volatile aroma compounds of Istrian dry-cured ham were found. Volatile compounds belonged to several chemical groups: aldehydes (51.4; 51.3%), terpenes (16.5; 16.4%), alcohols (15.5; 13.2%), ketones (8.6; 7.4%), alkanes (3.8; 5.7%), esters (1.3; 1.6%), aromatic hydrocarbons (0.8; 3.9%) and acids (0.6; 0.9%). Principal component analysis (PCA) showed that fat content, tenderness and melting texture were positively correlated. Terpenes were strongly correlated with flavour of added spices. Sweet taste and the presence of esters were positively correlated as well as negative odour, raw meat flavour and water content.     

Physicochemical changes throughout the ripening of dry cured hams with different salt content and processing conditions

Physicochemical characteristics of Semimembranosus and Biceps femoris muscles from 24 dry cured Iberian hams were analysed. The hams were salted with different amounts of salt (60 g kg^–1, HS, and 30 g kg^–1, LS, w/w) and then ripened at different temperatures (traditional processing, T, versus modified processing, M). The processing conditions did not significantly affect the moisture content and the chloride molality of Semimembranosus and Biceps femoris muscles (p>0.05) throughout ripening, although daily weight losses were significantly affected (p<0.01). The effect of the processing conditions on water activity was also rather limited as it was only significant at the drying stage. Colour a* values and chroma were significantly higher in Semimembranosus muscles from T hams than from M ones (p<0.01). Muscles from hams elaborated in a traditional system showed a higher number of tyrosine crystals than muscles from hams processed in a modified one, though only to a significant extent in Semimembranosus muscle (p<0.05). The salt concentration was higher in HS than in LS hams. HS hams showed higher weight losses in the salting and postsalting stages, owing to a more intense osmotic dehydration.     

Generation of volatile flavour compounds as affected by the chemical composition of different dry-cured ham sections

The composition of different dry-cured ham sections has been determined in order to study their contribution to flavour generation. The proteins, free amino acids, free fatty acids and volatile compounds were analysed in different sections of dry-cured hams with 7 and 12 months of processing. The main differences among sections were detected in free amino acids and volatile compounds. To sum up, there was a higher concentration of free amino acids in the centre section than in the butt and shank sections. However, after 12 m of ripening the difference among sections was lower and only the butt was the one with the lowest concentration. Similar results were obtained in the content of volatile compounds, the centre part of the hams contained a higher proportion of volatile compounds after 7 m of ripening than the shank and butt sections. Nevertheless, in 12 months dry-cured hams there are changes in the proportions of volatile compounds being the centre section the one with the highest proportion of volatile compounds due not only to the higher concentration of free amino acids but also to the oxidation of unsaturated fatty acids.     

SPME和SDE法提取的金华火腿与巴马火腿风味物质比较

金华火腿和巴马火腿分别经同时蒸馏（SDE）和固相微萃取（SPME）法提取,用气-质联用仪对其进行分析,结果表明：醇、醛、酮、酯、烷烃、含硫及杂环化舍物是两种干腌火腿的共有成分,且其风味组成相似,但各成分的含量存在明显差异。重要的火腿香味物质3-甲基丁醛、戊醛、己醛、庚醛、苯乙醛、2-辛烯醛、壬醛、辛醛、2,3-辛二酮、乙酸乙酯、1-辛烯-3-醇和癸酸等均由两种方法检出。两种方法均检出金华火腿中醛类和酸类含量较巴马火腿多,而巴马火腿中醛类和烷烃类或醇类的含量较金华火腿多。两种火腿采用两种方法检出的风味物质不同之处在于SPME法检出金华火腿的酸类物质种类和含量均较巴马火腿高,而SDE法检出巴马火腿的醇类物质的种类和含量均较金华火腿高。     

Effect of salt content and processing conditions on volatile compounds formation throughout the ripening of Iberian ham

Volatile compounds evolution throughout the ripening of dry-cured Iberian hams with different salt content (6% vs. 3% of salt w/w) and processing temperature conditions (traditional processing vs. modified processing) was studied using solid-phase microextraction coupled to a direct extraction device (SPME-DED). Traditional processing implied an increase in the temperatures (28 °C) during an intermediate period (drying phase) of the processing, while in the modified process temperature was maintained at 19 °C. Enhanced temperatures in the traditional processing did not increase compounds from lipid oxidation such as hexanal, heptanal, octanal or nonanal. Salt level did not show any effect on volatiles during processing except for 2-pentylfuran during the drying stage (day 177). Although none of the volatile compounds monitored showed significant differences in the final sampling, the ratio between hexanal and octanal plus nonanal, that of hexanal and 3-methylbutanal plus 2-methylbutanal and that of hexanal and γ-octalactone were significantly higher in hams processed under modified system, in which the temperature is lower in the drying stage.     

Development and validation of Computational Fluid Dynamics models for precision structural fumigation

Three-dimensional Computational Fluid Dynamics models for structural fumigation were developed and validated using Fluent^® based upon comprehensive data sets collected during the fumigation of a commercial flour mill. The external flow model, which included the flour mill and surrounding structures, was used to predict stagnation pressures on the mill's walls as a function of the wind speed and direction data. The pressure differences due to density differences between the gas inside and the air outside the mill (stack effect) were estimated using the environmental temperature and relative humidity data. The combined effect of the stagnation pressure and the stack effect was used as the boundary conditions of the internal flow model. The internal flow model incorporated interior details of the mill such as building plans, locations of major equipment, partitions and ducting. Because it was not possible to obtain the actual number and sizes of the cracks in the structure envelope, the idea of representing the cracks as effective leakage zones (ELZ) was adopted. The flow resistance coefficient, k_L, of the ELZs determines the gas tightness of the mill. Nine simulations were conducted with different k_L values. Both experimental and simulation concentration data indicated that the fumigant was uniformly distributed within the entire mill building. Using a manual optimization approach, one specific k_L value was determined for which the models were able to yield a half-loss time (HLT) value identical to the experimental HLT (17 h) and minimize the prediction of the concentration×time (Ct) product to within 10.5% of the observed value. Therefore, it was concluded that the models were validated and the assumption of ELZ was reasonable. The modeling methodology established in this paper could be utilized for the prediction of fumigation performance in any type of structure.     

Differentiation of yeasts growing on dry-cured Iberian ham by mitochondrial DNA restriction analysis, RAPD-PCR and their volatile compounds production

The efficiency of mitochondrial DNA (mtDNA) restriction analysis, RAPD-PCR and volatile compounds analysis to differentiate yeast biotypes involved in flavour development of dry-cured Iberian ham throughout the ripening process is evaluated. For this purpose, 86 yeasts isolated from Iberian hams in the main ripening stages at different industries of the four Protected Designations of Origin of this product, were used. The combination of mtDNA restriction analysis and RAPD-PCR using the primer (GACA)₄ showed a higher variability in the yeast species detected than obtained using only mtDNA restriction analysis. Only two species, Debaryomyces hansenii and Candida zeylanoides, were identified throughout the whole ripening process and a wide diversity of biotypes was found in these two species, with those of D. hansenii predominating. Clear differences between biotypes were detected in the generation of volatile compounds, with the biotype C2-2 of D. hansenii showing the highest concentrations of volatiles. The combined use of mtDNA restriction analysis and RAPD-PCR distinguishes yeast biotypes with different production of volatile compounds. In addition, analysis of the production profile of volatile compounds is needed to differentiate yeast strains of the same biotype recovered at different stages of ripening. Thus, the combination of these three methods could be very useful to select or monitor yeasts as starter cultures in dry-cured meat products.     

Influence of intramuscular fat content on lipid composition,sensory qualities and consumer acceptability of cured cooked ham

The present study is part of a project which aims to examine the influence of intramuscular fat (IMF) content on the sensory attributes and consumer acceptability of pork. An experiment was conducted to evaluate the influence of IMF level in muscle semimembranosus (SM) on the composition of its lipid fraction and on the sensory qualities and consumer acceptability of cured cooked hams. Thirty‐two carcasses were selected 24 h after slaughter from 125 Duroc × Landrace castrated male pigs showing large variability in SM muscle IMF content and were assigned to four IMF groups: ≤2%, 2–3%, 3–4% and >4%. Cured cooked ham slices were evaluated by a trained expert panel of 12 members and by a group of 56 consumers. Results from lipid analyses indicate that (i) an increase in IMF content was almost entirely reflected by an increase in the triglyceride content of the muscle and (ii) higher IMF levels were associated with higher free fatty acid and monoglyceride and lower cholesterol levels. The sensory evaluation of marbling significantly increased with IMF level, whereas other sensory qualities were unaffected. High IMF levels significantly depreciated the consumer perception of fat, aspect, taste and smell of ham slices. Overall, slices with the highest IMF levels got the least favourable rating by consumers. The present study indicates that increased IMF levels in muscle semimembranosus do not have significant effects on the sensory attributes of cured cooked hams, apart from the perception of marbling. However, high IMF levels have detrimental effects on the acceptability by consumers. © 2000 Society of Chemical Industry     

Influence of pig crossbreed on the composition, volatile compound content and flavour of dry cured ham

The extraction of volatile compounds from dry-cured ham using a dynamic head-space method coupled with gas chromatography mass-spectrometry (GC-MS) enabled the identification of a large number of components. Some of these compounds exhibited intense sensory characteristics during odour assessment. Using similar technology, the effect of pig crossbreeds: Landrace × Large-White, Duroc × Gascon-Meishan, Piétrain × Gascon-Meishan and Large-White × Gascon-Meishan, on both volatiles and the flavour of dry-cured hams was limited, although differences were observed in aromatic compounds like 1-octen-3-ol (mushroom), 2,3-butanedione and acetoin (butter like).     

Use of deodorized yellow mustard powder to control Escherichia coli O157:H7 in dry cured Westphalian ham

Dry cured (uncooked) hams with low water activity and pH ≥5.6 seem a likely food vehicle for Escherichia coli O157:H7. In previous work, isothiocyanates produced from mustard glucosinolates by bacterial myrosinase-like activity converted deodorized mustard into a potent antimicrobial in dry sausage. In this study its value in controlling E. coli O157:H7 survival in Westphalian ham was investigated. Hams were inoculated with a 7.5 log cfu g(-1) cocktail of E. coli O157:H7, 4% or 6% (w/w) deodorized yellow mustard powder was surface applied and monitored 80 d for pathogen survival. In one trial to accelerate formation of isothiocyanate, a Staphylococcus (S.) carnosus meat starter culture was added to hams at 45 d (after salt equilibration). At 21 d, E. coli O157:H7 was reduced by 3 log cfu g(-1) on hams treated with mustard powder compared to only a 1 log cfu g(-1) reduction in the control. By 45 d, mustard powder caused a reduction of >5 log cfu g(-1)E. coli O157:H7, whereas it took 80 d for numbers in control hams to be similarly reduced. Although the commercial process used caused a 5 log cfu g(-1) reduction of E. coli O157:H7 in 80 d, 4% or 6% deodorized mustard accelerated this reduction and the S. carnosus starter culture may have contributed to the maintenance of this effect.     

Effect of the pig rearing system on the final volatile profile of Iberian dry-cured ham as detected by PTR-ToF-MS

The volatile compound profile of dry-cured Iberian ham lean and subcutaneous fat from pigs fattened outdoors on acorn and pasture (Montanera) or on high-oleic concentrated feed (Campo) was investigated by proton transfer reaction time-of-flight mass spectrometry. In addition to the usual proton transfer ionization the novel switchable reagent ions system was implemented which allows the use of different precursor ions (H₃O⁺, NO⁺ and O₂⁺). The analysis of the lean and subcutaneous fat volatile compounds allowed a good sample discrimination according to the diet. Differences were evident for several classes of compounds: in particular, Montanera hams showed higher concentrations of aldehydes and ketones and lower concentrations of sulfur-containing compounds compared to Campo hams. The use of NO⁺ as precursor ion confirmed the results obtained with H₃O⁺ in terms of classification capability and provides additional analytical insights.