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.     

Efficacy of combining sulfuryl fluoride fumigation with heat to control the ham mite,Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae)

Sulfuryl fluoride (SF) could not control all life stages of Tyrophagus putrescentiae when applied at 23 °C using the highest allowable gas level. Recent work on heat treatments found 40 °C was ineffective against mites unless held for more than 48 h, a heating time that can damage ham quality. The objective of the laboratory trials reported here was to determine the lowest temperature and shortest exposure time at which SF could control mites while staying below the US EPA maximum concentration-time product (CTP) label rate of 1500 gh m⁻³ A 36-h fumigation with a CTP of 1400 gh m⁻³ killed 100% of all mite life stages at 40 °C. Mite eggs, which were determined to be the most SF-tolerant life stage, were exposed to lower CTPs of 300 or 1000 gh m⁻³ SF at 40 °C, control was estimated to require up to 125.71 h at 300 gh m⁻³ and 60.93 h at1000 gh m⁻³. Applying heat with SF just below the maximum allowable CTP will increase the efficacy of this fumigant, but also increases the risk of exceeding the legal limit for the gas. However, at target CTPs of either 300 or 1000 gh m⁻³, which would represent preferred commercial application rates of SF, good levels of mite control could not be achieved at 40 °C within a 48-h exposure.     

Effects of temperature,relative humidity,and protective netting on Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae) infestation,fungal growth,and product quality of dry cured hams

Since methyl bromide is an ozone depleting substance, there is a need to find effective alternative methods to control mite infestations on dry cured hams. Therefore, the objective of this study was to determine the most effective relative humidity and/or temperature combination to minimize mite reproduction and mold growth on dry cured hams in untreated and food-grade ingredient infused nets. Food grade coating formulations of 1) xanthan gum and propylene glycol, and 2) carrageenan, propylene glycol alginate, and propylene glycol nets were infused into nets. Dry cured ham cubes and slices were wrapped with untreated and treated nets, inoculated with 20 large mixed-sex mites per cube or 50 large mixed-sex mites per slice, and then stored for 14 d at each temperature (24, 28, and 32 °C) and RH (55, 65, 75, and 85%) combination in an environmental chamber. Tyrophagus putrescentiae on ham slices in untreated nets were reduced from the initial inoculum level of 50 mites per ham slice when exposed to 85% r.h. at 24, 28, and 32 °C. Nets infused with xanthan gum and propylene glycol or carrageenan, propylene glycol alginate, and propylene glycol, completely inhibited mite reproduction at 85% r.h. In addition, the nets infused with carrageenan, propylene glycol alginate, and propylene glycol, controlled mite reproduction below the initial inoculum level on ham cubes and ham slices at all temperatures and relative humidities that were evaluated. Six to eight trained panelists rated the amount of mold on the ham slice surfaces on a 0–100% scale and both treated nets evaluated were effective at preventing mold growth on the ham slices.     

Biology and integrated pest management of Tyrophagus putrescentiae (Schrank) infesting dry cured hams

The biology and physiology of Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae), also known as the ham, cheese or mold mite, is reviewed along with methods that have been evaluated for managing and controlling this pest. This review was conducted because the ham mite is an important target pest of the dry cured ham industry. Methyl bromide has been historically used to control mite infestations, but is now banned or being phased out of use in most countries because it is an ozone-depleting substance. Only commercially available stockpiles and quarantine and pre-shipment methyl bromide are available for use in countries that require such action. This review compares the effectiveness and feasibility of recently investigated methods to control mite infestations on dry cured ham and to discuss integrated pest management plans for ham mites. The review also proposes methods for conducting a prevention and monitoring-based integrated pest management program that relies on definitive mitigation such as fumigation only when mite numbers exceed a critical action threshold.     

Sulfuryl fluoride as a methyl bromide alternative for fumigation of Necrobia rufipes (Coleoptera: Cleridae) and Tyrophagus putrescentiae (Sarcoptiformes: Acaridae), major pests of animal-based stored products

Sulfuryl fluoride (SF) has been registered in many countries for stored product applications as an alternative to other fumigants, especially methyl bromide (MB). Research was conducted to establish SF fumigation protocols for the mortality of pests infesting post-harvest durable commodities. The efficacy of SF against two major arthropod pests of southern dry-cured hams, the red-legged ham beetle, Necrobia rufipes, and the ham mite, Tyrophagus putrescentiae, was investigated. SF caused significant mortality in ham beetles but not for ham mites when treated for 48 h at 23 °C. Eggs of N. rufipes were more tolerant to SF than other stages fumigated. In addition, early aged (1–2 d old) eggs of N. rufipes were more susceptible to SF than late-aged (4–5 d old) eggs. Furthermore, SF fumigation led to 100% control of larvae, pupae and adults of N. rufipes by 8 g/m³ while the eggs required 20.88–24.72 g/m³ to prevent 100% hatch. However, T. putrescentiae showed high tolerance to SF as it survived concentration-time products in excess of the standard label limit 1500 g h/m³. SF studies also revealed that the eggs of T. putrescentiae were several fold more tolerant than that of the mobile stage, the nymphs and adults. SF trials under pilot-scale commercial conditions were also carried out that further supported the efficacy of SF for red-legged ham beetles but not for the ham mite. SF may not be suitable for managing ham mites based on work to date, but future work could investigate longer exposure times at higher temperatures.     

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.     

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.     

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.     

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.     

Effect of Iberian × Duroc genotype on composition and sensory properties of dry‐cured ham

BACKGROUND: Dry‐cured ham quality from three different Iberian × Duroc genotypes was studied: GEN1, Iberian × Duroc1; GEN2, Duroc1 × Iberian; GEN3, Duroc2 × Iberian. GEN1 and GEN2 are reciprocal crosses, while the difference between GEN2 and GEN3 is the Duroc sire line. The line Duroc1 (DU1) was selected for the manufacture of dry‐cured meat products, whereas the line Duroc2 (DU2) was selected for meat production with low carcass fat. RESULTS: Dry‐cured hams from all genotypes had similar chemical composition. However, intramuscular fat of dry‐cured hams from GEN3 was more unsaturated than that from GEN2, while GEN1 was intermediate. Lipid oxidation, measured as 2‐thiobarbituric acid‐reactive substances (TBARS) and hexanal content, was similar between genotypes. The colour of hams was affected by genotype; hams from GEN2 showed higher lightness (CIE L*), while those from GEN3 had a less intense colour (lower a* and C*). Texture measured instrumentally did not differ between genotypes; however, in the sensory analysis, panellists considered hams from GEN3 more fibrous, while those from GEN2 were considered juicier. Hams from GEN3 were also perceived as saltier and more acid. CONCLUSION: Genotype affected the quality of Iberian hams, with those from GEN3 being of lower quality, and this genotype was considered less suitable for the manufacture of Iberian dry‐cured ham. Copyright © 2007 Society of Chemical Industry     

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.     

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.     

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.     

The application of food grade short chain fatty acids to prevent infestation of Tyrophagus putrescentiae on dry cured ham and the effects on sensory properties

Tyrophagus putrescentiae (ham mite) is difficult for commercial dry cured ham producers to control. Methyl bromide is an effective fumigant but is now banned as an ozone depleting substance, meaning alternative methods to control mite infestation must be found. This research was conducted to test the efficacy of C₈C₉C₁₀ fatty acids combined with and without food grade coatings to control mite infestations on dry cured hams. Ham cubes were coated directly or wrapped in nets saturated with C₈C₉C₁₀ with combinations of either soybean oil, xanthan gum (XG) or carrageenan (CG) + propylene glycol alginate (PGA). Cubes were then inoculated with 20 large mixed sex ham mites and stored for 14 days at 22 ± 2 °C and 70 ± 5% relative humidity. The soybean oil alone or in combination with 10% C₈C₉C₁₀ in direct coating, and 1% and 10% C₈C₉C₁₀ in coated nets controlled mite population growth. In addition, the use of 10% C₈C₉C₁₀ + XG and 10% C₈C₉C₁₀ + CG + PGA in direct coatings or in saturated nets, and 1% C₈C₉C₁₀ + XG in saturated nets also inhibited mite population growth. Unexpectedly, the soybean oil solvent by itself effectively controlled mite population growth as well. Sensory evaluation was performed using a difference from control test (n = 8) and indicated that only 10% C₈C₉C₁₀ mixed with soybean oil and 100% soybean oil did not impart sensory differences to ham when used as a coating. However, for ham slices treated in saturated nets and gum with C₈C₉C₁₀ mixtures in either coating or saturated nets did impart sensory differences. Results indicated that C₈C₉C₁₀ and soybean oil could be used in coating formulations to control ham mites but long-term testing, sensory evaluation, and scaled up testing is needed prior to industrial implementation.     

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。     

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.