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 brine thawing/salting on endogenous enzyme activity and sensory quality of Iberian dry-cured ham

Simultaneous brine thawing/salting process was applied as an alternative to traditional pile salting process using 51 frozen Iberian hams. The effect of this type of salting process on endogenous enzyme activity and sensory quality of Iberian dry-cured hams was analysed. The frozen hams were simultaneously thawed and salted with saturated brine, with and without vacuum pulses, and were compared to hams thawed under refrigeration and traditionally salted. The peptidase and lipase activities were measured at the end of salting and post-salting stages. The activity of cathepsin B+L was reduced in the two brine salted batches while few differences among batches were observed for the other peptidases. Several lipase activities were significantly reduced in the two brine salted batches. The brine thawed processing affected the free fatty acid content at the different stages although the differences were more appreciated at the beginning of the process and no differences were observed at the end. The long ripening time makes these differences negligible and the consumer did not appreciate any differences between the sensory quality of Iberian brine/thawed hams and traditional Iberian thawed pile salted hams.     

Time-related changes in cathepsin B and L activities during processing of Jinhua ham as a function of pH, salt and temperature

Sixty experimental Jinhua hams were processed by traditional methods using green hams from local crossbred pigs of Lanxi, Zhejiang province, PR China. Biceps femoris was sampled from five hams randomly taken after each processing stage. Potential activities of cathepsin B and L were determined. The effects of temperature, salt content, pH value and nitrate content on the activities of cathepsin B and L were evaluated using response surface methodology (RSM) and the actual activities of cathepsin B and L during Jinhua ham processing were calculated. The results showed that potential activities of cathepsin B and L decreased gradually from 11332.05 to 9955.50 Ug(-1) prior salting to 1055.32-1359.90 Ug(-1) at the end of post-aging, respectively. After processing, about 9.31% original potential activity of cathepsin B and 13.66% original potential activity of cathepsin L were left. Temperature, pH value and salt content showed significant effects on cathepsin B and L activities. By stepwise regression analysis, two quadratic regression equation models were built individually for estimating cathepsin B and L activities. The models predicted that the actual activities of cathepsin B and L were less than 5% of their corresponding potential activities most of the time before half of loft-aging and about 15% and 20% during the rest processing periods. Nevertheless, cathepsin B and L retained actual activities throughout processing, especially during loft-aging and post-aging periods.     

Analysis of raw meat to predict proteolysis in Parma ham

Four hundred and thirty-seven pigs (223 purebred Italian Large White, 97 Italian Landrace, and 117 Duroc), were studied to examine the effect of breed on meat quality and assess the possibility of relating proteolysis of dry-cured hams to raw meat quality. The Duroc pigs had intramuscular fat contents and water holding capacities (M. Semimembranosus) significantly higher than those of the Large White and Landrace. The latter had a significantly higher pH(24h) and cathepsin B activities significantly lower than the Duroc breed. The dry-cured hams (M. Biceps femoris) from the three breeds were significantly different in proximate composition, proteolysis and weight loss at the end of ageing. Data for green hams (including salt content) were used to compute a model to fit the proteolysis of the corresponding dry-cured hams. The variables included in the model (R(2)=0.53 and P<0.01) were cathepsin B activity of raw ham, pH(24h), weight loss after the first salting step, and the salt content of the dry-cured ham. The raw hams with the highest cathepsin B activities, the lowest pH(24h), and the highest weight loss after the first salting were those in which greatest proteolysis occured.     

Effects of high-pressure processing on proteolytic enzymes and proteins in cold-smoked salmon during refrigerated storage

The present paper describes the effects of high-pressure processing on the activity of proteolytic enzymes in cold-smoked salmon and enzyme extracts for pressures up to 300 MPa. The activities of the three enzymes, cathepsin B-like, cathepsin B + L-like and calpains were reduced at all pressure levels of up to 300 MPa (at ca. 9 °C for 20 min) in crude enzyme extracts prepared from cold-smoked salmon. Calpain almost completely inactivated at 300 MPa. High-pressure did not influence general proteolytic activity but activated the enzymes in muscles at higher pressure levels studied until 18 days of storage. An increase in the activity of cathepsin B + L-like and calpain was seen after 12 days of refrigerated storage. Myosin heavy chain was less affected at higher pressure levels (300 MPa) only as shown by Sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) of proteins and further refrigerated storage had no obvious effects on proteins.     

The effect of green ham pH and NaCl concentration on cathepsin activities and the sensory characteristics of dry-cured hams

There is a tendency to reduce the amount of NaCl in the manufacturing process of Spanish dry-cured ham. NaCl, pH and temperature determine the stability of this product. This study was concerned with the evaluation of green ham pH and sodium chloride concentration on cathepsin activities, physico-chemical parameters and sensory characteristics of dry-cured hams. Two different amounts of salt (55 and 80 g kg⁻¹) and two different pH levels (pH at 24 h post mortem <5·8; pH at 24 h post mortem >6·2) were used. Physico-chemical composition, cathepsin activity and a number of sensory parameters were evaluated. Hams with high pH displayed lower cathepsin activity, NPN, saltiness and hardness whereas the levels of brightness, crumbliness, pastiness and adhesivity were found to be higher than in normal hams. A high level of salt produced greater cathepsin B and B+L activity and lower pastiness and adhesivity than the samples with a low NaCl level. © 1998 SCI.     

Comparison of calpain and cathepsin (B,L and D) activities during dry-cured ham processing from heavy and light large white pigs

Calpain and cathepsin (B, L and D) levels in the Semimembranosus and the Biceps femoris muscles were determined during dry-curing of hams from heavy and light Large White pigs, to evaluate the use of heavy pigs in the production of high quality dry-cured hams. Calpains were detected only in green hams and after the salting step, while cathepsins were observed throughout the curing. Hams from heavy pigs showed lower enzyme levels than hams from light pigs, particularly in green hams. The lower levels could be attributed to the slower protein turnover of heavy pigs. Commercial improvement by means of slow curing processes on heavy White hams is suggested.     

Effects of high pressure treatment on the proteolytic enzymes in meat

This paper describes the effects of high-pressure treatment on proteolytic enzymes in muscle, especially catheptic enzymes which influence meat tenderization, and on acid phosphatase, used as an index of disruption of lysosomal membranes. Acid phosphatase activity in the extract from pressurized muscle increased with increasing pressure applied to the muscle up to 500 MPa. Activity of cathepsin B, D and L increased up to 400 MPa, then tended to decrease at 500 MPa. Cathepsin H and aminopeptidase B decreased with the increasing pressure. Measurements of enzymic activity in the pressurized crude extract, to investigate the pressure effect on the enzymes themselves, showed that all enzymes studied in this paper lost their enzymic activity as applied pressure increased. When the pressurized extracts were subjected to the gel-filtration chromatography, a decrease in the activities of cathepsin H and aminopeptidase B and an increase in the activities of cathepsins B and L and acid phosphatase were observed. It seems that the decrease in activity of the enzymes eluted early from the column (cathepsin H and aminopeptidase B) is due to decrease in the amount of protein eluted by the pressure treatment, whereas the increase in activity of the enzymes eluted late (cathepsin B, L and acid phosphatase) is due to an increase in the amount of protein eluted. From the results, it was concluded that the pressure-induced increase in the amount of protease activity in the muscle was due to the release of the enzymes from lysosomes.     

Effect of high-pressure treatment on the survival of Listeria monocytogenes Scott A in sliced vacuum-packaged Iberian and Serrano cured hams

High-pressure treatment is useful for increasing the microbiological safety of ready-to-eat foods. With dry-cured hams, this treatment can be applied to the finished product after slicing and vacuum packaging. The effect of high-pressure treatment on the survival of inoculated Listeria monocytogenes Scott A and on the sensory characteristics of two Spanish dry-cured hams, Iberian and Serrano, was investigated. Ham slices were inoculated with L. monocytogenes at 6 x 10(6) CFU/g and held at 4 degrees C for 20 h before high-pressure treatment. During this holding period, the population of the pathogen declined by 0.44 and 0.51 log CFU/g in Iberian and Serrano hams, respectively. Treatment at 450 MPa for 10 min at 12 degrees C reduced L. monocytogenes populations by 1.50 and 1.16 log CFU/g in Iberian and Serrano hams, respectively. During the first week of storage at 4 or 8 degrees C, L. monocytogenes populations declined by an average 0.89 log CFU/g in pressurized Iberian ham and 2.09 log CFU/g in pressurized Serrano ham. After 60 days at 4 or 8 degrees C, the respective populations in pressurized and control hams were 3.24 and 4.70 log CFU/g for Iberian ham and 2.73 and 5.07 log CFU/g for Serrano ham. The color parameters L* and a* were not influenced by high-pressure treatment, and parameter b* was increased only in Iberian ham. Sensory characteristics of hams were not affected by high-pressure treatment. Treatment of Iberian and Serrano hams at 450 MPa for 10 min significantly reduced the population of L. monocytogenes Scott A without a detrimental effect on the sensory characteristics of the hams.     

Effects of high pressure application (400 and 900 MPa) and refrigerated storage time on the oxidative stability of sliced skin vacuum packed dry-cured ham

The effect of high pressure processing at 400 MPa and 900 MPa on the oxidative stability of sliced and vacuum packaged commercial dry-cured ham was determined by analyzing the antioxidant enzyme activities, TBARS levels (thiobarbituric acid reactive substances), vitamin E content and physicochemical characteristics during refrigerated storage for 50 days in different light conditions. In dry-cured ham pressurized at 400 MPa color changes and sensory analyses were also assessed. The high pressure process at 900 MPa produced a decrease in superoxide dismutase (SOD) and glutathione peroxidase (GSHPx) activities and increased vitamin E content. In contrast, pressurization at 400 MPa, increased SOD activity, and showed no effect on vitamin E content and GSHPx activity. In general the physicochemical parameters determined (fat, moisture and collagen) were unaffected by pressurization. Treatment at 400 MPa increased the instrumental color measurement of lightness (L* values, CIELAB). This level of pressure also modified the hardness, chewiness, saltiness and color intensity. These changes of the sensory attributes in dry-cured ham were significant, but small.     

PROTEASES IN FRESH PORK MUSCLE AND THEIR INFLUENCE ON BITTER TASTE FORMATION IN DRY-CURED HAM

Legs from 10–12 month old heavy pigs were assayed for cathepsin B and peptidase activities, and dry-cured following regulatory standard procedures. Dried hams were analyzed for proximate muscle (biceps femoris) composition, free amino acids (FAA), enzyme activities and perception of bitter taste by a trained sensory panel. Protein breakdown, measured by nonprotein nitrogen (NPN), and FAA content were greater in the more bitter samples, as were cathepsin B and dipeptidyl (DPP I and DPP II) activities. In contrast, hams with null or mild bitter intensity exhibited higher aminopeptidase activities in both the fresh and aged muscle. A distinct FAA pattern was found for each class with the bitter hams being abundant in methionine, asparagine and isoleucine and less rich in tyrosine, arginine and ornithine.     

Effect of low-temperature preservation on the quality of vacuum-packaged dry-cured ham: Refrigerated boneless ham and frozen ham cuts

The effect of storage on dry-cured ham quality was studied. Sixteen vacuum-packaged boneless dry-cured hams and sixteen vacuum-packaged dry-cured ham cuts were stored in darkness under refrigeration (4±2°C; 8 months) or freezing (-18±1°C; 24 months), respectively. Instrumental colour and texture, physico-chemical and biochemical parameters, sensory profile and consumer acceptability and purchase satisfaction were measured throughout storage. The overall quality of refrigerated boneless dry-cured hams and frozen dry-cured ham cuts showed only limited changes throughout long-term storage. Significant changes involved loss of odour and flavour, increased adhesiveness and modification of hardness, the Semimembranosus muscle became tender while Biceps femoris became harder, leading to a higher textural homogeneity. In agreement with those changes, the overall acceptability assessed by a trained panel decreased throughout storage, though this was significant regarding only frozen hams. However, consumer evaluation of acceptability, as well as satisfaction with hypothetical purchasing, did not vary significantly throughout storage.     

Pattern of Muscle Proteolytic and Lipolytic Enzymes from Light and Heavy Pigs

Samples of muscle Semimembranosus were removed from light and heavy pork hams 3 days after slaughtering and analysed for chemical composition and proteolytic and lipolytic enzyme activity. Light hams were higher in moisture content and cathepsin (B and B+L) activity, and lower in peptidase (pyroglutamyl and dipetidyl IV) activity; the absence of further differences in proteolytic and in lipolytic enzymes could be due to large variation coefficients found within both ham classes. The use of principal components analysis displayed distinct patterns for light and heavy samples, with the latter being mainly characterised by greater peptidase-to-proteinase ratio and, to a lesser extent, by higher lipase activity. It was concluded that different chemical and enzyme patterns in fresh meat might be the cause of the wide variations in protein and lipid breakdown mechanisms that are often encountered in dry-cured pork derivatives.     

Changes on enzymatic activity and on sarcoplasmic and myofibrillar proteins of frozen-stored hake (Merluccius merluccius) pre-treated by high pressure

High-pressure (HP) pre-treatments were applied on European hake (Merluccius merluccius) followed by a frozen accelerated experiment (−10 °C). A central composite design ranging pressure levels (150–450 MPa) and frozen storage time (0–150 days) was used, being evaluated the enzymatic activities and muscle proteins. Acid phosphatase and calpain activities decreased after 150 days of frozen storage (58%/56% and 38%/56% for non-/HP-treated samples, respectively). Cathepsin B showed higher reductions (98%) for longer storage times. Furthermore, HP and frozen storage did not affect significantly cathepsin D activity, only slightly decreasing at 169 MPa. Furthermore, HP seemed to not affect myofibrillar proteins, while sarcoplasmic proteins were clearly affected by HP and frozen storage time, resulting in a reduction of about 53% or 23% for 431 or 450 MPa, respectively. Thus, HP could be used to lowering the deleterious effect of proteases on frozen European hake.     

A method for identification of frozen meat used for production of cooked ham

A simple method to distinguish if the meat used for production of cooked hams was frozen or unfrozen was developed. Several analytical parameters of quality in meat products (general and colour parameters and protein fraction) were determined in two types of cooked hams: one elaborated with refrigerated (R) and another with frozen and thawed (F/T) raw hams. Student's t-test was applied to compare both groups, but it could not be concluded if R and F/T cooked hams had the same quality or not. For this reason two multivariate statistical analyses, Factor (FA) and Discriminant Analysis (DA), were applied. The application of FA resulted in the separation of the two groups of cooked hams and allowed the selection of the parameters which were used in Discriminant Analysis (DA). A discriminant function, that is both easy to use and to interpret, was obtained.     

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.     

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.     

Influence of high pressure application on the nutritional, sensory and microbiological characteristics of sliced skin vacuum packed dry-cured ham. Effects along the storage period

The effect of high pressure processing at 600 MPa on sliced and vacuum packaged commercial dry-cured ham was determined by analyzing the induced color changes, the physicochemical characteristics, the microbiological count and the changes in sensory attributes and also its effect on lipid oxidation measured through TBARS (thiobarbituric reactive substances), antioxidant enzyme activities and the content of fatty acid from total, free and phospholipid fractions. This effect was also studied during 50 days refrigerated storage with different light conditions. The high pressure processing at 600 MPa modified the color of dry-cured ham producing an increase in lightness L*-parameter. Many sensory attributes were also modified resulting in an increase in hardness, chewiness, brightness, odor intensity and saltiness, while reducing color intensity. High pressure produced a reduction in the aerobic count. The oxidative stability of the pressurized dry-cured ham was not altered as observed from the absence of differences in fatty acid contents and antioxidant enzyme activities. Initially pressurization produced a decrease in TBARS levels, however this effect was not found after 50 days of refrigerated storage.

Industrial relevance

The application of high hydrostatic pressure (HHP) in food technology is a useful tool to combine a minimal processing that increases the shelf-life of the food products, maintaining their safety and nutritional properties and with minimal changes in flavor or taste. This processing technology is very important to increase the safety of the sliced foods which are prone to the microbiological deterioration, as cured meat products and cooked ham. Pressurization of sliced dry-cured ham at 600 MPa has been shown effective reducing spoilage associated microorganisms. The present study was carried out to evaluate the oxidative stability, nutritional quality, safety and sensory attributes of dry-cured ham pressurized at 600 MPa. This is very important because the hypothesis that HHP does not affect to sensorial characteristics needs to be confirmed in different kind of foods. Also, the possible causes of the observed effects should be explained by the study of physic–chemical parameters. In this way the oxidative stability is an important issue because some authors claimed that HHP can increase oxidation in food containing lipids.     

Structural and Textural Quality of Kinu-Tofu Frozen-then-Thawed at High-Pressure

To determine effects of high-pressure thawing on quality of high-pressure frozen tofu, kinu-tofu (soybean curd) was frozen 90 min at ca ?20°C at 100 MPa (ice I), 200 MPa (liquid phase), 340 MPa (ice III), 400, 500 or 600 MPa (ice V), then thawed at the same pressure. Texture and structure of this tofu (D) were compared with high-pressure-frozen tofu thawed at atmospheric pressure (A: 90 min frozen; B: 90 min frozen then 2 days at ?30°C; C: 160 min frozen). When tofu was frozen at 200- 500 MPa, ice crystals were largest to smallest in B > A and C > D; pore size of D was the same as untreated tofu. Results indicated ice crystals never grew when frozen at 200–500 MPa. Growth occurred during reduction of pressure at ca ?20°C, frozen storage or while thawing at atmospheric pressure due to phase transition.     

Activity of cathepsin B, D, H and L in Spanish dry-cured ham of normal and defective texture

Thirty-six specimens of Spanish dry-cured ham from 18 different batches were studied to determine the influence of endogenous enzymes on the textural quality of the end product. It was shown that, the residual enzyme activity of cathepsins B+L is a reliable indicator of textural defects associated with strong proteolysis in Spanish dry-cured ham. In contrast, the activity of cathepsin B, which varied widely among samples, was less influential. Salt levels can have a moderate effect on the residual enzyme activities. Other compositional parameters also influence the properties of the end product; the amount of protein in semimembranosus muscle was found to be less and the moisture greater in texturally defective specimens. Also, the efficiency of the drying-curing process was less in hams yielding poor textures.