Edward Pospiech

Changes of myofibrillar and centrifugal drip proteins and shear force of psoas major and minor and semitendinosus muscles from calves, heifers and cows during post-mortem ageing

Changes in myofibrillar protein content and centrifugal drip proteins of psoas major and minor (PM) and semitendinosus (ST) muscles of calves, heifers and cows taken from carcasses on the 1st, 6th and 12th day of post-mortem cold storage were estimated. Washed myofibrils and centrifugal drip from muscles were analysed using SDS-PAGE 10 and 12% polyacrylamide gels. No significant changes were observed in content of contractile proteins, α-actinin and regulatory proteins (except for TN-T). There were no significant differences between muscles from investigated groups and between muscles aged in chilled conditions. The levels of titin T1 during ageing varied slightly. The 30 kDa-fraction appearance was fastest in calf, slower in heifer and slowest in cow muscles. More pronounced differences in the level of protein degradation with regards to muscle type, age of animals and time of storage were found in the centrifugal drip of meat. In the drip, the level of high molecular weight proteins was higher in muscles from young animals and in the muscles stored longer. The opposite was observed in case of 26-28 kDa proteins. Their amount in muscle drip decreased with increased storage time. The rate of proteolysis and release of cytoskeletal proteins during cold storage of muscles were related to change in shear values of roasted meat. The highest rate of protein degradation was observed in PM calf muscle and the lowest rate in ST cow muscle. The fastest tenderization process was registered in calves muscles and the slowest tenderization in cows.

The effect of the packaging system and storage time on myofibrillar protein degradation and oxidation process in relation to beef tenderness

This study investigated the impact of packaging systems on the degradation and oxidation of beef proteins regarding beef tenderness of longissimus lumborum (LL) and biceps femoris (BF) muscles stored in vacuum skin packaging (VSP), a modified atmosphere with high oxygen concentration (MAP), and combined of these two methods (VSP+MAP). A significant decrease in the Warner-Bratzler shear force (WBSF) in VSP at D14 and D28 for LL was observed compared to BF. A significant effect of packaging system on troponin-T (Tn-T) and desmin degradation was shown (p≤0.001). A high concentration of oxygen in MAP and VSP+MAP affected protein oxidation, which was reflected in myosin oxidative cross-linking. An increase of WBSF values detected in steaks packed in VSP and VSP+MAP systems could be caused by the intensification of protein oxidation. Furthermore, BF was more susceptible to oxidation compared to LL. The VSP+MAP packaging system has resulted in the maintenance of a bright, red color, however has not improved the beef tenderness.

Proteomic analysis of Lupinus angustifolius (var. Zeus and Bojar) and Lupinus luteus (var. Lord and Parys) seed proteins and their hydrolysates

BACKGROUND Proteins enzymatic digestion is a very complex process, during which some components are degraded, whereas others remain in an unchanged form. Moreover, enzymatic hydrolysis is one of the most popular methods used to reduce the allergenicity of food proteins. In the present study, the efficiency of enzymatic hydrolysis of lupin seed proteins was assessed by proteomic analysis as performed by two-dimensional gel electrophoresis (2-DE) coupled with mass spectrometry identification. Two digestion systems were used: oriented digestion carried out by trypsin and model in vitro digestion mimicking the conditions present in the gastrointestinal tract. RESULTS The comparisons of 2-DE maps of proteins isolated form different lupin seed species revealed that the differences in proteins expression were observed mainly in the central parts of gels (i.e. in the molecular weight range from 20 to 70 kDa, and the pH range 5-7). In total, 27 differentially expressed proteins spots were successfully identified by mass spectrometry analysis. An important reduction in the number of proteins spots on 2-DE maps was observed when trypsin and the in vitro digestion model were applied. The protein spot insensitive to digestion in both hydrolysis systems was identified as β-conglutin. CONCLUSIONS The results of the present study provide insight into the nature of the digestion process that may take place after lupin seed protein intake and highlight the important fact that some of the proteins are insensitive to digestive enzyme activity. Moreover, evaluation of digestion activity of trypsin towards lupin seed proteins may be used for the development of specific processes with respect to hypoallergenic food production.

Changes in glycolysis process in bulls’ meat carcasses subjected to different tenderization treatments

Background. Electrical stimulation and conditioning of carcasses are carried out to improve the quality of meat. The aim of the study was to evaluate the effect of these treatments on the glycolysis process and tenderness of beef. Material and methods. The longest lumbar muscles (m. longissimus lumborum) were the experimental material. They were divided into four groups by tenderization treatments: ES – high voltage electrical stimulation, KD – conditioning for 18 h at a temperature of 12–15°C, ES+KD – electrical stimulation and conditioning, in conjunction, K – standard cooled carcasses. Glycolysis was evaluated on the basis of the pH value, the content of glycogen and lactic acid after 45 min, and 3, 14, 17, 21, and 28 days post mortem. Tenderness was measured on the 3rd, 14th, 17th, 21st and 28th day based on shear force evaluations. Results. At 45 min after slaughter the value of pH of the muscles was decreasing at the highest rate in the case of ES and ES+KD. Meat of those carcasses displayed the best tenderness after 3 and 14 days, especially when compared to K samples (p ≤ 0.05). Conclusions. Among the evaluated meat tenderization treatments, ES had the greatest impact on improving meat tenderness. The conjunction of ES and KD did not cause significant changes in the process of glycolysis and meat tenderization.

20. The Effect of Muscle Type and Time of Storage on Myofibrillar Protein Proportion in Beef

Abstract Tenderness is usually associated with the proteolysis occurring in muscles. However, most of the studies concentrate on one muscle only. The aim of this study was to describe the changes in myofibrillar protein percentage proportions during the ageing of 8 bovine muscles. Investigations were conducted on the muscles from different parts of the carcass, from the forequarter: m. pectoralis profundus, m. infraspinatus, m. triceps brachii, m. serratus ventralis, and from the hindquarter: m. biceps femoris, m. semimembranosus, m. semitendinosus and m. longissimus dorsi (thoracis et lumborum). The effect of muscle type was significant for all parameters except for percentage proportions of titin (3000÷3700 kDa), MHC (205 kDa) and protein fractions between <205÷42> kDa. Differences between the muscles varied depending on the analysed proteins and the time of storage. A significant effect of ageing time for titin, nebulin (approx. 800 kDa), proteins of molecular weight of 38 kDa, proteins smaller than 42 kDa and in the range of 3000÷205 kDa, 205÷42 kDa and 38÷20 kDa was observed. The decrease of percentage proportions of titin, nebulin and proteins in the range of 3000÷205 kDa and an increase of protein bands in the range of 38÷20 kDa and proteins below 42 kDa was also observed. During the storage period of beef from the 2nd to the 14th day, the progress of myofibrillar proteolysis was different in each muscle. The changes of tenderness were not related to shear force values. It is probable that the changes in other constituents of meat might influence the tenderness more than those in myofibrillar proteins.

Detection of allergenic additives in processed meat products: Allergens in meat products

Allergic responses to food components are an increasing problem all over the world. It is therefore important to protect people who are vulnerable to food allergens against accidental and unintended consumption of products containing allergic ingredients. The meat industry commonly uses various allergic additives in the production of processed products, such as legumes (soy, peas, beans), milk and egg preparations, cereals containing gluten (wheat, rye, barley and oats), and spices (celery and mustard). These meat additives have specific technological properties, which help to create a texture or flavor profile, or affect the nutritional value, although some of them, such as soy, mustard, milk and egg white proteins, can cause severe allergic reactions. The aim of this paper is to discuss the application of various recently established methods of detection of allergenic additives in processed meat products - for instance cold cuts and sausages. The new methods are based mainly on protein, DNA, and isoflavones or phytic acid analysis. The article also characterizes the latest trends in the development of research on methods that would enable quick and reliable identification of targeted allergens in meat products.

Immunoreactivity changes during lupin seed storage proteins digestion

Lupin seeds are already widely used as an ingredient in different food products. Their attractiveness is related mainly to their high protein content that is characterised by a favourable amino acid composition, as well as the desired technological properties. However, with the increase of lupin seeds usage in food manufacture, their potential allergic properties have been demonstrated. The aim of this work was to study the immunoreactivity changes taking place during the enzymatic hydrolysis of the major seed proteins of narrow-leafed (Lupinus angustifolius, varieties Zeus and Bojar) and yellow (L. luteus, var. Lord and Parys) lupin species. Two digestion systems were used, namely the in vitro model simulating digestion taking place in digestive track, and specific hydrolysis carried out by trypsin. The obtained hydrolysates were analysed by means of one-dimensional electrophoresis, and their immunoreactivity was assessed with the use of a sera pool from patients with lupin-specific IgE. An important reduction in allergenicity of lupin seed proteins was observed when trypsin digestion was applied. The digestion in the in vitro model revealed the possibility of formation of neoallergens which were identified on the basis of mass spectrometry results as β-conglutin fraction.