Influence of lipid type on water and fat mobility in fermented sausages studied by low-field NMR.

The effects of diacylglycerols (DAG), pork back fat and sunflower oil on water and fat mobility in fermented sausages were studied with (1)H NMR relaxometry. The added fat affected the physicochemical parameters weight loss, water activity, moisture content and moisture content on a defatted-dry-matter basis of reduced-fat non-acid fermented sausages. The weight losses were the lowest in sausages prepared with DAG and sunflower oil, which resulted in higher water activity compared to sausages prepared with back fat. The relaxation times related to fat mobility differed between fat types and increased in the order: control

Estimation of dry-cured ham composition using dielectric time domain reflectometry.

Development of real-time, non-destructive methods to characterize dry-cured ham is of interest to the food industry. Since dielectric properties change depending on the composition of the food product studied, time domain reflectometry (TDR) could be a useful method to characterize dry-cured ham. In this study, samples with different compositions were measured with a TDR device equipped with an open-ended coaxial line sensor. Partial least square regression (PLSR) analysis was used to develop predictive models to determine salt, water and fat contents and a(w) in dry-cured ham. Results show that salt content (RMSEV=0.22%), water content (RMSEV=1.67%) and a(w) (RMSEV=0.0087) can be accurately determined, though fat content is determined with less precision (RMSEV=2.81%). Saltiness, dryness and fatness of the samples, in the studied range, did not affect the accuracy of the predictions. Developed predictive models were accurate enough to consider the TDR device as a useful tool for characterizing and classifying dry-cured ham in industry.

Analysis of raw hams using SELDI-TOF-MS to predict the final quality of dry-cured hams.

The relationship between protein profiles of Gluteus medius (GM) muscles of raw hams obtained from 4 pure breed pigs (Duroc, Large White, Landrace, and Piétrain) with the final quality of the Semimembranosus and Biceps femoris muscles of dry-cured hams was investigated. As expected, Duroc hams showed higher levels of marbling and intramuscular fat content than the other breeds. Piétrain hams were the leanest and most conformed, and presented the lowest salt content in dry-cured hams. Even if differences in the quality traits (colour, water activity, texture, composition, intramuscular fat, and marbling) of dry-cured hams were observed among the studied breeds, only small differences in the sensory attributes were detected. Surface-enhanced laser desorption/ionisation time-of-flight mass spectrometry (SELDI-TOF-MS) was used to obtain the soluble protein profiles of GM muscles. Some associations between protein peaks obtained with SELDI-TOF-MS and quality traits, mainly colour (b*) and texture (F(0), Y(2), Y(90)) were observed. Candidate protein markers for the quality of processed dry-cured hams were identified.

Reduction of NaCl content in restructured dry-cured hams: Post-resting temperature and drying level effects on physicochemical and sensory parameters.

The effects of post-resting temperature (5°C, 15°C and 25°C) and drying level (low and high, corresponding to final water contents (w/w) of 57% and 50%, respectively) were evaluated in restructured dry-cured hams. The reduction of NaCl content, with and without the addition of K-lactate as NaCl substitute was also evaluated. Physicochemical and instrumental colour and texture (Stress Relaxation test) parameters and sensory attributes were measured. The main effects of reducing the NaCl addition from 30g/kg to 15g/kg in restructured dry-cured hams were the reduction of saltiness and the increase of a(w), proteolysis and softness. The addition of K-lactate (19.7g/kg) contributed to reduce these effects. Hams from high drying level had a longer processing time and a higher proteolysis index, but lower water content and harder texture. The increase of post-resting temperature to above 5°C reduced the processing time and the metallic flavour, but at 25°C restructured hams were spoiled. Therefore, the problems due to the reduction of NaCl to 15g/kg in restructured dry-cured hams can be reduced by adding K-lactate and drying at 15°C (after 3.5months of resting at 5°C) until a final weight loss of around 45% is reached.

Effects of potassium lactate and high pressure on transglutaminase restructured dry-cured hams with reduced salt content.

Ten raw hams (from 5 carcasses) were boned and salted either with salt reduction (15g/kg NaCl) or salt reduction with addition of potassium lactate (15g/kg NaCl and 39.74g/kg of a 60% K-lactate solution). Subsequently, the ham pieces were assembled together with transglutaminase, vacuum packed into water-permeable plastic bags and kept at 3°C and 85% RH until reaching above 30% weight losses. The effects of K-lactate addition and the high-pressure (HP) treatment at 600MPa on the physicochemical, instrumental colour and texture (Tensile test) and sensory characteristics of the biceps femoris (BF) muscle were evaluated. The addition of K-lactate did not have a negative effect on colour, flavour or texture of restructured dry-cured hams. The HP treatment increased significantly the pH, L(∗), a(∗) and b(∗) values and the breaking stress, and decreased the water-holding capacity and elasticity (apparent Young's modulus) of BF muscle. The HP treatment also affected significantly the flavour (increasing saltiness, umami and sweetness) and the sensory texture attributes (increasing muscle binding, hardness, gumminess and fibrousness and decreasing adhesiveness and pastiness), as well as slice appearance (increasing brightness and iridescence and decreasing colour homogeneity).

Eating quality of young bulls from three Spanish beef breed-production systems and its relationships with chemical and instrumental meat quality.

Sensory characteristics of longissimus thoracis muscle from three local Spanish beef breed-production systems and their relationships with chemical and instrumental meat quality traits were studied. Young bulls of Bruna dels Pirineus (BP; n=69), Avileña-Negra Ibérica (A-NI; n=70) and Morucha (MO; n=70) breeds were reared in their own production systems. MO breed showed the highest water holding capacity and also the highest thawing loss and haem pigment content (P<0.001). No differences in moisture and protein contents were found among breeds. A-NI showed the highest intramuscular fat (IMF, P<0.05) and total collagen (P<0.001) contents, whereas BP showed the lowest IMF content (P<0.05) and the highest collagen solubility (P<0.001). Beef flavour, tenderness and juiciness accounted for the eating quality differences among the three breed-production systems. Meat from A-NI was rated significantly higher (P<0.01) for beef flavour and tenderness than that from BP and MO animals. Furthermore, MO showed the lowest juiciness (P<0.001) which could be due to its higher thawing loss. Within the three breeds, thawing loss was negatively correlated with juiciness and, likewise cooking loss with juiciness and tenderness (P<0.05). The canonical discriminant analysis showed that the three breeds were significantly different (P<0.05) from each other according to sensory attributes, which justifies their involvement in different protected geographical indications (PGI).

Texture changes in dry-cured ham pieces by mild thermal treatments at the end of the drying process.

The present study evaluated the effects of mild thermal treatments at the end of the drying process on physicochemical characteristics and instrumental and sensory texture in dry-cured ham. Experiment 1: effect of thermal treatments (4-46°C) for 4h and 24h. Experiment 2: time effect (4-168h) of thermal treatments at 30°C and 36°C. Both experiments were done on small dry-cured ham dices. Experiment 3: time effect (4-168h) of thermal treatment at 30°C on both instrumental and sensory texture of 4-cm-thick sections of dry-cured ham. The thermal treatment at 30°C for 168h on both dry-cured ham muscle dices (20mm×20mm×15mm) and dry-cured ham sections (4cmthick) decreased softness, adhesiveness and pastiness in BF muscle, without increasing hardness in SM muscle or affecting moisture, a(w) and proteolysis index.

Effect of a 10-day ageing at 30°C on the texture of dry-cured hams processed at temperatures up to 18°C in relation to raw meat pH and salting time.

The aim of this study was to investigate the effect of a 10-day ageing at 30±2°C on the texture of dry-cured hams processed at temperatures up to 18±2°C for 12 months in relation with raw ham pH and salting time. Three pH groups (semimembranosus muscle at 24h post-mortem: Low pH<5.7, Medium pH=5.7⩽pH⩽5.9, and High pH>5.9), three salting times (6d, 10d and 14d) and two ageing temperatures (18°C and 30°C) were investigated. Physicochemical characteristics, instrumental and sensory texture and product sliceability were evaluated on biceps femoris and semimembranosus muscles. Hams with pH(SM24)<5.7 should be avoided in order to reduce the incidence of texture problems in dry-cured ham elaboration. Texture problems are especially important in hams with a reduced salt content that are mechanically sliced (not frozen). A 10-day ageing at 30°C could be useful for reducing the soft texture problems in dry-cured hams processed at temperatures up to 18°C for 12 months without affecting the product flavour.

Colorectal stenting as an effective therapy for preoperative and palliative treatment of large bowel obstruction: 9 years' experience.

BACKGROUND: Since their introduction, selfextending metal stents (SEMS) have established themselves as an option in the treatment of obstructive colorectal cancer. Thanks to stenting, patients traditionally treated with emergency surgery can now be converted to scheduled surgery with mechanical preparation of the colon and primary anastomosis. Stenting represents a valid one-step surgical alternative for intestinal obstruction of the colon. METHODS: We performed a prospective study of 95 patients (mean age, 68 years; range 48-94) with large bowel obstruction due to colorectal cancer treated with SEMS placed under fluoroscopic guidance, some as a bridge to surgery (group A) and others with palliative intent (group B). Computed tomography was performed for diagnostic purposes and to study the extent of disease. RESULTS: Treatment was palliative in 28 cases (group B) and as a bridge to surgery in 67 (group A). The latter group underwent mechanical preparation of the colon and elective surgery. No patients died as a result of the procedure. In 90 cases (95%), treatment was effective and the obstruction resolved. Complications were 4 cases of perforation, 1 of tenesmus, 4 obstructions and 4 migrations. In 7 cases, a second stent was inserted to allow subsequent scheduled surgery. CONCLUSIONS: Self-extending stents resolve colorectal cancer obstruction and allow optimal patient staging and scheduled surgical treatment. Stenting is also a useful option in advanced or irresectable tumors, avoiding the need for surgery and offering good palliation.

Microwave heating of cooked pork patties as a function of fat content.

In this study, the parameters heating rate, dielectric factors, and specific heat capacity, which determine the heating profiles and the dissipation of energy during microwave heating, were obtained for precooked pork patties. The pork patties studied were lean meat, pure back fat, and several lean meat/back fat mixtures. Microwave heating at 798 W power was not sufficient to accelerate the heating rates in 100% lean meat compared to 415 W. However, samples were able to heat up faster and dissipate more energy at 798 W power as fat content increased and moisture content decreased. The recorded differences in the specific heat capacity of the studied materials as a function of temperature seemed not to be the key factor to explain the observed temperature rises. Temperature rise seemed to have more to do with the interactions of fat with the electromagnetic field, and with viscosity changes during phase transitions. Trends found for the dielectric properties over microwave heating of meat products agree with data from other authors, but the influence of parameters related to the sample composition and structure should be taken into account. The dissipation factors (epsilon''/epsilon') provided a good approximation to the capacity of the samples containing lean meat and the lean meat/fat mixtures to transform the electromagnetic energy into heat. Neither the dielectric constant nor the loss or dissipation factors were able to clarify the high amount of energy transformed into heat in 100% back fat. Penetration depth and reflected power indicated that back fat allowed microwave energy to be repeatedly redirected to the material.

Instrumental evaluation of defective texture in dry-cured hams.

In the first experiment, the effect of the stress relaxation time on texture evaluation of biceps femoris (BF) muscle from dry-cured hams was studied. The specimens were compressed to 25% of their original height and the crosshead speed was 5mm/s. The force decay versus time was recorded and Peleg's model was fitted with different relaxation times. Whatever relaxation time was used, Peleg's model did not describe simultaneously the initial fall of force and the asymptotic tendency of force decay correctly. The initial force and force decay at 2s and at 90s are proposed to assess texture in dry-cured ham. In the second experiment, stress relaxation (SR) and texture profile analysis (TPA) tests were performed on BF and semimembranosus (SM) muscles of 10 hams with abnormal softness and 10 hams with normal texture, at different assay conditions: sample temperature (4°C or 20°C); compression crosshead speed (1mm/s or 10mm/s). The instrumental texture test and the assay conditions that detected defective textures better depended on the muscle considered: for BF muscle the SR test at 4°C and at 1mm/s and for SM muscle the TPA test at 10mm/s at both 4°C or 20°C.

Technologies to shorten the drying period of dry-cured meat products.

Dry-cured meat products are well-known for their unique sensory characteristics. However, the traditional process is very time consuming. The process can be shortened especially by accelerating the drying period, which is the most time consuming. This paper deals with some technological, safety and sensorial aspects for producing fermented sausages and dry-cured hams when the process time is shortened. Different techniques, such as temperature increase and thickness reduction, and the effects of some ingredients and additives are discussed. A Quick-Dry-Slice process based on a continuous system that combines both convective and vacuum drying could accelerate the drying of slices after the desired pH is reached in fermented sausages. There are safety concerns when processes are shortened, but possible additional hurdles, such as the introduction of bacteriocin-producing starter cultures and high-pressure treatments at the end of the process, could reduce them. Methods to speed up the development of typical colour, texture and flavour and their limitations are also discussed.

Softness in dry-cured porcine biceps femoris muscles in relation to meat quality characteristics and processing conditions.

The aim of the study was to quantify the effect of meat quality characteristics and some processing conditions on the softness of dry-cured biceps femoris (BF) muscles. The BF muscles were dissected from forty hams and classified according to their pH(BF) into three groups: LpH (pH<5.66), MpH (5.66⩽pH⩽6.00) and HpH (pH>6.00). BF muscles within each pH(BF) group were distributed into three different Salting levels (1%, 2% or 4% of added NaCl). Muscles were salted, vacuum-packed and stored at 3°C for 30 days. The post-salting BF muscles were classified into two intramuscular fat (IMF) levels: Low (IMF<4%) and High (IMF⩾4%). Thereafter, the muscles were divided into two pieces and dried at two of the three different Drying levels (1.5, 2 and 2.5g H(2)O/g desalted dry matter). Then, each piece was divided into two samples that were packed in N(2) and stored at 5°C or 30°C for 1 month. Stress Relaxation was used to evaluate texture. Dry-cured BF muscles with initial pH>6.0, with IMF>4% or with added NaCl levels less than 2% were more prone to show soft texture. Softness in dry-cured muscles can be reduced by applying an ageing temperature of 30°C for 30 days, despite increasing proteolysis. The softness reduction by ageing at 30°C compared with 5°C is expected to be higher when applied to drier samples, which show a smaller increase in proteolysis.

High pressure applied to frozen ham at different process stages. 1. Effect on the final physicochemical parameters and on the antioxidant and proteolytic enzyme activities of dry-cured ham.

This paper describes the effect of high pressure (400MPa and 600MPa) applied to frozen hams at early stages of the dry-cured ham process: green hams (GH) and hams at the end of the resting stage (ERS), on some physicochemical parameters and on antioxidant and proteolytic enzyme activities in the final product. No significant differences were observed among treatments either in the drying kinetics or in the physicochemical characteristics. However, when high-pressure was applied to frozen GH hams it produced a superficial denaturation that affected salt absorption and, consequently, the proteolysis index. The high-pressure treatment applied during the processing of previously frozen GH and ERS hams reduced the antioxidant enzyme activities slightly (superoxide dismutase, catalase and glutathione peroxidase) but did not affect the cathepsin B and the cathepsin B+L activities.

High pressure applied to frozen ham at different process stages. 2. Effect on the sensory attributes and on the colour characteristics of dry-cured ham.

This paper describes the effect of high pressure (400MPa and 600MPa) applied to frozen hams at early stages of the dry-cured ham process: green hams (GH) and hams at the end of the resting stage (ERS), on the appearance, some texture and flavour parameters and on the instrumental colour characteristics of dry-cured hams. Pressurized hams showed slightly lower visual colour intensity than the control ones. In general, pressurization did not have a significant effect on the flavour characteristics of the final product. The 600-MPa hams from the ERS process showed significantly lower crumbliness and higher fibrousness scores than the control and the 400-MPa hams. However, none of these differences were enough to affect the overall sensory quality of the hams negatively. Regarding instrumental colour characteristics (L(∗)a(∗)b(∗)), an increase in lightness was observed in the biceps femoris muscle from GH hams pressurized at 400MPa and 600MPa but not in the ERS hams.

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.

Texture parameters of dry-cured ham m. biceps femoris samples dried at different levels as a function of water activity and water content.

Instrumental texture parameters of m. biceps femoris (BF) samples from six commercial dry-cured hams, dried to a different degree, were related to water activity and water content. Samples were carved into cubes and Texture Profile Analysis (compression 50%, 10 mm high samples), water activity (a(w) 25 °C) and water content analyses were performed. A negative non-linear relationship between hardness and water content and water activity was observed. From this relationship, critical X and a(w) values, below which there is a dramatic increase in hardness, can be found (around 0.55 kg H(2)O/kg dry matter and around 0.70, respectively). Cohesiveness and springiness showed a positive linear relationship with water content and water activity.

Profiles of water content, water activity and texture in crusted dry-cured loin and in non-crusted dry-cured loin.

This study compares the profiles of water activity (a(w)), water content (X) and texture in loin with crusted surface versus those profiles in loin without crust, and establishes a mathematical model able to describe hardness based on a(w) and/or X. Two loins (m. longissimus dorsi) were dry-cured, aged and then each one was divided into four pieces. Two of them were dried at 15±2 °C, 50±3% RH (CL treatment) and the other two were dried at 2±2 °C, 80±3% RH (NCL treatment). The pieces of CL were dried under more severe conditions in order to develop a crust on the surface. Three-millimetre thick slices were taken from the most external part towards the inner part. The slices were prepared (10×10×3 mm) for texture profile analysis (TPA). Measurements of a(w) and X were carried out on each slice. Variance analyses and non-linear regression analyses were performed to create a model for loin hardness prediction through X and/or a(w) and a linear regression model for cohesiveness and springiness. CL loins showed a higher hardness and chewiness and lower cohesiveness at the surface (3-mm thickness) than the NCL loins. Hardness and chewiness, fitted with a non-linear model, were better described by X than by a(w). Springiness showed a low relationship with X and a(w). The on-line monitoring of X and a(w) at the surface of the product would enable an estimation of the profiles of water content, a(w) and texture and it could be, therefore, a useful tool to avoid crusting.

Relationship between water content, NaCl content, pH and texture parameters in dry-cured muscles.

The aim of the present study was to describe the effect of NaCl and pH on the relationship between water content and hardness, cohesiveness and springiness in dry-cured muscles. 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 on the semimembranosus muscle at 24-h postmortem. The semimembranosus and biceps femoris muscles were cut from hams, cured and individually packaged in bags and were laid in trays in a room at 2±2°C for 45days. Thereafter nine samples from each muscle were shaped like a parallelepiped and dried until different levels of drying, ranging from 28.5% to 59.7% water content, were attained. The rest of the muscle was ground and packaged until its subsequent physicochemical analysis. At the end of the drying period, a Texture Profile Analysis was used to determine textural parameters. The results indicated that for a range of X (kg H(2)O/kg dry matter) between 0.8 and 1.3 the hardness remains practically unchanged while for X<0.6 the hardness increases substantially. The samples from hams with low pH(SM) had greater hardness, cohesiveness and springiness than those from hams with high pH(SM). Dry-cured muscles with lower NaCl content showed lower hardness, cohesiveness and springiness, especially in those with pH(SM)>6.2. At X values lower than 0.6 the hardness was more influenced by water content than by NaCl content or pH(SM).

Characterisation of young bulls of the Bruna dels Pirineus cattle breed (selected from old Brown Swiss) in relation to carcass, meat quality and biochemical traits.

Seventy-four young bulls of the Bruna dels Pirineus beef cattle breed were reared in a typical production system and slaughtered at an average age of 381 days and live weight of 541 kg. The animals were evaluated for productive traits, carcass quality, meat quality, eating quality and biochemical characteristics of m. longissimus thoracis (LT). Biochemical measurements included intramuscular fat (IMF) and collagen proportion, haem pigment concentration, lactate dehydrogenase and isocitrate dehydrogenase activities and type I (MHC I) fibre percentage determined by ELISA. Bruna dels Pirineus bulls achieved high growth rates during the fattening period (1.63 kg/day) and showed good carcass quality, with a high dressing-out proportion (607 g/kg, hot carcass), a good conformation score (U; EUROP) and a moderate fatness score (3;1-5). Carcass composition was estimated from the sixth rib joint dissection (682 g/kg lean proportion, 127 g/kg total dissectable fat and 163 g/kg bone). IMF (24.3 g/kg) and MHC I (27.9%) showed high variabilities (CV>30%). Sensory analysis of LT included beef and livery odour and flavour intensity, and overall tenderness and juiciness assessment of loin samples (14-day ageing). Beef odour and flavour were slightly positively correlated with IMF and carcass fatness score (P<0.05). Fatness, MHC I, insoluble collagen and cooking losses tended to affect the livery flavour intensity positively. This variable was significantly higher in meat from bulls of lower carcass quality (i.e. lower conformation score, lower lean proportion; P<0.05) and higher type I fibre percentage. Loin overall tenderness and juiciness were not affected by the biochemical traits studied, however, they were negatively affected by cooking loss (P<0.05).