Quantitative histological analysis of bovine small intestines before and after processing into natural sausage casings.

A histological study was undertaken to determine the efficiency in the removal of the mucosa and Peyer's patches by standard processing of bovine intestines into natural sausage casings. The second objective was to calculate the quantity of lymphoid and nervous tissue per consumable sausage. For the histological analysis, intestinal samples were collected from 80 beef cattle during the slaughter process. Fresh and cleaned intestines were compared in analyzing the thickness of the intestinal wall, weight reduction during cleaning, removal of the mucosal layer, and the presence of lymphoid and neural tissue after cleaning. The obtained data indicate a weight reduction of about 50% during standard cleaning procedures, as 90% of the mucosa and 48% of the lymphoid tissue are removed. Based on the quantitative histological image analysis, it was calculated that 1 m of cleaned casings, weighing on average 64 g, contains about 2.8 g of mucosa, 0.3 g of lymphoid tissue, and 0.1 g of neural tissue. Assuming, in a worst-case scenario, that the sausage casing is ingested when consuming 200 g of sausage at one meal, this consumption includes 0.09 g of lymphoid tissue and 0.02 g of neural tissue as part of the sausage casing. These data can be included in a risk assessment on the potentialexposure of consumers to bovine spongiform encephalopathy infectivity after eating sausages in beef casings.

Comparative histological studies of mechanically versus manually processed sheep intestines used to make natural sausage casings.

The natural sausage casings industry is large and worldwide, and casings prepared from the small intestine of sheep form a large part of it. Food safety authorities in several countries have been concerned about the risk to consumers from the bovine spongiform encephalopathy (BSE) agent. Although this agent could enter the European small ruminant population via infected feed, there is no evidence that it has. Because the BSE agent introduced experimentally into sheep and goats has a tissue distribution very similar to that found in animals with natural cases of scrapie, the agent would likely be found in the intestine and lymph nodes of some infected sheep from an early age. When natural casings are prepared from the intestine, the ileum (known to be infected in animals with natural cases of scrapie) is removed and the intestine is cleaned such that the inner (tunica mucosa) and outer (tunica serosa and tunica muscularis) layers are removed, leaving only the submucosa. There are two main methods for cleaning the intestine: manual and mechanical. The cleaning efficiency of these two methods was examined in the commercial environment as practiced on healthy sheep considered fit for human consumption in Turkey and Great Britain. The investigation involved a qualitative and quantitative histological approach. There was no significant difference in cleaning efficiency between the two methods, although there was some variation. No Peyer's patches or residues of them were found in any part of the cleaned casings. This finding is important because in sheep infected with transmissible spongiform encephalopathies (TSEs) Peyer's patches are likely to contain a major part of the intestinal infectivity. No serosa was found in any casing, but some residual mucosa and muscularis was retained, with more of the former than the latter. The results indicate that the cleaning efficiency of the two methods was broadly equivalent, that there was significant removal of tissue that could promote TSE infection, and that TSE risk reduction likely would be achieved by both methods, although this probability could not be quantified by the methods used in this study.

[Local and regional veterinary history]. / Lokale en regionale veterinaire geschiedenis.

Continuing a review, written in 1992, an overview is given of the five recent studies on local themes. The author emphasizes that telling a story of local traditions and usages, of striking personalities or personal experiences can illuminate the problems of a broader national or even international context. He points to the fact that the local archives contain many materials of veterinary historical relevance waiting for exploitation.

Immunohistochemical detection of brain tissue in heated meat products.

Immunohistochemical methods were used to determine whether brain tissue could be detected in test batches of meat products prepared with known levels of this tissue (0, 1, 5, 10, or 20% bovine brain tissue or 5% porcine brain tissue). Four different, commercially-available antibodies were examined: anti-Neurofilament (anti-NF), anti-MyelinBasicProtein (anti-MBP), anti-NeuronSpecificEnolase (anti-NSE) and anti-GlialFibrillaryAcidicProtein (anti-GFAP). Results obtained with the four antibodies differed with the heat treatment applied to the products (pasteurisation or sterilisation). The amount of immunoreaction product in the raw meat product varied with the antibody, even when the sample contained the same amount of brain tissue. The staining pattern also varied with the antibody. Overall, the anti-MBP antibody proved to be most useful in detecting brain tissue in finely comminuted heated meat products.

[Feminization of veterinary medicine in the Netherlands 1925-2000]. / De feminisering van de diergeneeskunde in Nederland, 1925-2000.

The feminisation of veterinary medicine occurred in The Netherlands, as elsewhere in the world, in the course of the twentieth century. In 1930, Jeannette Voet (1907-1979) was the first female veterinarian graduate of the Faculty of Veterinary Medicine of Utrecht University. In contrast with the first Dutch female physician who graduated in 1878, Jeannette Voet was not an active feminist. Instead, she concentrated on the development of various fields of veterinary medicine during her career. Nevertheless, she played an important role in the acceptance of women in Dutch veterinary medicine. The integration of women into all areas of the veterinary profession was a gradual process. Meat inspection, in particular, proved to be rather conservative in its acceptance of female veterinarians. The number of women veterinarians in the profession increased only gradually throughout the twentieth century. In 1970, women represented not more than 5 % of all veterinarians in The Netherlands. A significant increase in female students was first observed in the 1980s. The large influx of city girls who are primarily interested in companion animal and horse medicine is still quite remarkable. The average percentage of female first-year students between 1988 and 1992 was 60; over the last 5 years, this increased to 70%. Between 1988 and 1999, the average percentage of female graduates grew from 35 to 60%. Consequently, the proportion of Dutch female veterinarians increased from 5 to 25% between 1970 and 2000. In spite of this development, the representation of women veterinarians among policymaking officials, leading veterinary authorities and academic staff (particularly at the professor level) is still quite low. From this point of view, veterinary medicine could still be considered as 'a man's job'. Feminisation of veterinary medicine is often explained by an increase in the numbers of companion animals and horses and part-time jobs or by a different, gender-based attitude towards animals. Another, simpler, explanation is that fewer male students are attracted to veterinary medicine because they can make more money in other professions. More historical sociological research, including a comparison with feminisation in other sciences and broader society, is necessary to obtain a deeper insight into this phenomenon. Regardless, feminisation is likely to further change the veterinary profession in the near future.

[From horse doctor to cow leech to veterinary manager. Regulation of the market for veterinary services in historical perspective]. / Van paardendoctor-koemeester tot veterinair manager; regulering van de veterinaire markt in historisch perspectief.

In the course of the last two centuries veterinarians succeeded in gaining a monopoly with respect to a number of specific tasks within society under the motto "to the benefit of man and animal alike". Today, a veterinary infrastructure exists in the western world, which is usually taken for granted by society. Before the responsibility for maintaining animal resources and protecting both animal and human health were entrusted to veterinarians, both the process of scientific progress and professionalization of veterinary medicine were necessary. In this paper the regulation of the market for veterinary services in The Netherlands is decribed. Until World War II, the military and the colonies represented a major demand for veterinary services. A healthly livestock has always been considered as a main concern by the Dutch government with respect to the domestic food supply as well as exports. State intervention concerning veterinary medicine therefore focused on the organized campaigns against livestock diseases. Early national veterinary legislation originated from this concern, as is still the case today within the EU framework. The protection of human health only became part of the veterinary professional domain at a relatively late stage. Due to a strong economic growth from the 1960s onwards, veterinary practice was extended with the care for an increasing number of companion animals. The veterinary profession and its employment are subject to changes in society, such as the number of animals and the significance that is paid to the different species. In 1900 there were 4 million production animals in The Netherlands, while the human population counted 5 million. One century later, not less than approximately 130 million farm animals and 30 million companion animals are living in this country, which now has about 16 million inhabitants. Consquently, the total number of active vets increased from about 250 to 4,000 in the same period, while the number of group and solo practices both increased.

Effect of initial mild curing, with additives, of hog and sheep sausage casings on their microbial quality and mechanical properties after storage at difference temperatures.

Sausage containers, derived from animal intestines, are usually preserved by salting and/or drying. Adequately salted final products are microbiologically fully acceptable. However casings, even those packed in dry salt, sometimes deteriorate in quality. Experiments were performed to improve salting procedures by adding food-grade additives to the salt to improve the microbiological and mechanical properties of the casings. Before storage, casings were cured by slush- or dry-salting with or without additives for 3 weeks, and after that the rinsed and re-salted (dry- or slush-salting) casings were stored for 6 months at different temperatures (10, 20, and 40°C). During storage, growth of halophylic bacteria was observed in control casings (salted, no additives) but not in casings cured with citric or lactic acid and their relative sodium salts. The casings cured with citric acid/Na(3)-citrate had good mechanical properties and filling characteristics when assessed after prolonged storage at 10°C.

Determinants of tenderisation in beef Longissimus dorsi and Triceps brachii muscles.

Tenderisation of bovine Mm. longissimus dorsi and triceps brachii and factors impacting tenderisation were studied. Mm. longissimus dorsi and triceps brachii of 12 Friesian-Holstein cows (age 3-11 years; 212-349 kg carcass weight) were sampled at various times post mortem (p.m.) for determination of pH, temperature, fibre type and morphology, connective tissue distribution, SDS-PAGE of myofibrillar proteins, Warner-Bratzler shear force, sarcomere length and osmolality. The stretched position of the M. triceps brachii (sarcomere length 2.35 ± 0.24 µm) resulted in a relatively low shear force at 1 day p.m. (6.2 ± 0.9 kg/cm(2)) with further storage having little additional effect. M. longissimus dorsi entered rigor in a more contracted state (sarcomere length 1.65 ± 0.11 µm), resulting in a relatively high shear force at 1 day p.m. (10.3 ± 2.3). Stepwise linear regression was used to calculate the best 1- to 3-variable equations for shear force of M. longissimus dorsi at 1, 7 and 14 days p.m. and the decrease in shear force between 7 and 14 days p.m. Shear force at 1 day p.m. appeared to be determined mainly by the speed of pH- and temperature-decline. Proteolysis of myofibrillar proteins and animal age appeared to be the main determinants for shear force at 1 and 14 days p.m. The average surface area of type I fibres could explain part of the variation in the decrease in shear force between 1 and 14 days p.m.

Mechanical and microstructural characteristics of meat doughs, either heated by a continuous process in a radio-frequency field or conventionally in a waterbath.

Meat doughs, all having the same chemical composition, were pasteurised to a comparable heat intensity (calculated as Cook values: target level of 5 min at 100°C): (i) while flowing through a glass tube (inner diameter 50 mm) mounted in a special radio-frequency (27 MHz) heating section; (ii) after flowing unheated through the glass tube at the same rate and heated in a waterbath; and (iii) after sampling immediately after the pump and heated in a waterbath. The cooked products were sampled in the core and at the rim of the product for rheological (oscillation and uniaxial compression tests at small strain), fracture measurements (uniaxial compression tests at high strain) and microstructural evaluation (light microscopy and video image analysis). Additional core samples were used for a sensory evaluation (triangle tests) of the texture of the differently processed doughs. The fast heating rate (25-30 K/min) at a mass flow of the dough of 100 kg/h (mean velocity 0.014 m/s) during dielectrical pasteurisation affected the mechanical character, the microstructure and the triangle test results of core samples from the sausages, compared to heating in a waterbath. Flow of the unheated dough through the tube of the continuous processing equipment, followed by heating in a waterbath, had little effect on the results of the mechanical tests, the microscopical evaluation and the triangle tests. The radio-frequency heated products had both higher storage and loss moduli (were more firm), fractured at higher stress values and were considered more firm in the sensory evaluation. The microstructure of dielectrically heated versus other samples displayed a more open structure of the protein matrix with larger irregularly shaped fat particles that were surrounded by relatively thin and compact protein bridges. The effects of flow and heating method on the behaviour of rim samples were very similar to their effects on the core of the products. A comparison of the mechanical behaviour of core and rim samples only was significant for radio-frequency heated doughs. The rim samples had lower storage and loss moduli and fractured at lower stress values than the core samples. Micrographs of the dielectrically heated rim versus core samples displayed more orientation of connective tissue particles in the direction of flow and of elongated, larger and irregularly shaped fat particles. Probably, shear at the wall of the tube affected the characteristics of the rim samples. All heated doughs displayed hardly and cooking losses. The radio-frequency heated products always displayed a thin layer of moisture on their surface and occasionally a little fat separation.

Changes in lightness of porcine lean meat batters during processing.

The pattern of changes of lightness (L(∗)) for porcine lean meat batters (PLMBs) with time was divided in two phases: chopping process (Phase 1) resulting in a sharp increase of L(∗), and the subsequent storage of the batters for 24 h at 15°C (Phase 2). During Phase 2, L(∗)-values decreased with time approximating a plateau. The subjects of study were effects on the course of L(∗) of: (1) added sodium chloride and phosphate in Phase 2, (2) the fate of air bubbles embedded in the batters in Phases 1 and 2, and (3) changes in light absorption by the pigment myoglobin in Phase 2. (1) Sodium chloride and phosphate appeared to have very little impact on the changes in L(∗) during storage of the PLMBs at 15°C, although microstructural changes were distinct. (2) Continuous entrapment of air during the chopping process had a major effect on the increase of L(∗) in Phase 1, air bubbles being scattering elements in the PLMB. Disproportionation caused a decrease in the number of small air bubbles, resulting in a decrease of L(∗) during the early stage of Phase 2 (about 35 min), immediately after the chopping stage was finished. (3) Strong evidence was obtained that shifts in the absorption traits of pigments (red nitric oxide myoglobin was formed at the cost of grey met-myoglobin) during the period from 1 to 5 h, caused a marked decrease in the pattern of L(∗) during Phase 2.

Utility of immunohistochemical identification of muscle proteins in microstructural studies of comminuted meat products.

A series of experiments was conducted in an attempt to immunohistochemically identify specific muscle proteins in raw bovine muscle, meat batters and finely comminuted meat products. Three different antibodies were investigated-monoclonal anti-actin (IgG), polyclonal anti-desmin (IgG) and polyclonal anti-myoglobin (IgM). In addition, the fluorescent compound nitrobenzooxadiazole (NBD)-phallacidin was tested. The utility of the antibody anti-desmin proved to be poor. Anti-myoglobin and NBD-phallacidin were useful in muscle tissues that had been technologically treated to a limited extent. Anti-actin reacted with actin present in raw muscle tissue, in muscle samples comminuted with and without additives and in muscle samples that had been comminuted with additives and subsequently heated to 80°C and 115°C. However, its reactivity was markedly more distinct in raw than in processed samples. The utility of current immunohistochemical techniques to study the microstructure of processed meats seems to be limited due to the rapid denaturation of the specific muscle proteins.

[Hygienic aspects of pig's head meat. 2. Mechanical separation of pigs' heads]. / Hygiënische aspecten van varkenskopvlees. 2. Mechanisch separeren van varkenskoppen.

Deboning pigs' heads is a labour-intensive process. According to information supplied by the industry, mechanical separation of pigs' heads offers good prospects. Data on the hygienic implications of this process were not known. These were studied more closely in an experimental design. The bacteriological and sensory qualities as well as the chemical and histological composition of the product were compared with those of manually obtained pig's head meat. In addition, the yield of the process of separation was determined. Three groups of heads were mechanically separated, viz. untreated heads and heads which had previously been dipped in water having an initial temperature of 100 degrees C for one minute and five minutes respectively. These studies served to verify the fact that mechanical separation of pigs' heads is technically possible. Previous dipping of the heads in water at a temperature of 100 degrees C produced a considerable improvement of the yield in meat, which was due to setting of the rind. The chemical composition of the product was roughly identical with that of manually obtained head meat. However, tissue composition and structure of the tissues differed markedly. An important drawback is the higher count of Enterobacteriaceae in the product. These bacteria are probably released on compression from sites which are difficult of access such as the nose, the pharyngeal cavity and the alveoli. In addition, they may be possibly protected by a covering layer of mucus. Therefore, mechanical separation is not regarded as acceptable from the point of view of hygiene.

[Hygienic aspects of pig's head meat. 1. Obtaining and processing pigs' heads]. / Hygiënische aspecten van varkenskopvlees. 1. Winning en bewerking van varkenskoppen.

Pigs's head meat is mainly obtained in specialised deboning plants and provides raw materials for the manufacture of meat products and snacks. Few data on hygiene in processing and production of pig's heads or on the bacteriological quality and tissue composition of pig's head meat have so far been published. The object of the present investigation was to supplement these data and to examine the extent to which this quality could be improved by Good Manufacturing Practices (GMP's). A total number of 11 slaughter-houses and 14 deboning plants were studied. Hygiene was assessed by two investigators on the basis of a check list. Temperatures of rooms, heads and head meat were measured. Twenty-one samples (7 x 3) were taken in each of nine deboning plants for bacteriological and histological examination. The investigations carried out in slaughter-houses showed that pig's heads were only washed in five out of eleven slaughter-houses. Cleansing and disinfection of the apparatus used in splitting the carcasses were omitted or merely carried out incidentally during slaughter. Assessment of hygiene in the deboning plants ranged from adequate to satisfactory in 13 out of 14 plants. The average aerobic colony count in Log N g-1 of pig's head meat was 6.7 +/- 0.7; this was 4.4 +/- 0.9 for counts of colony-forming units (CFU) of Enterobacteriaceae. Tonsils, mucous membranes, bone, hair and dirt were found to be present in 8, 13, 21, 39 and 9 per cent of the samples respectively. As a result of the manual cleavage of heads, relatively large bone particles (greater than 8 mm) were detected in the head meat. It is concluded that an improvement of the hygienic quality of pig's head meat can mainly be achieved by taking more care in obtaining pig's heads.

[Identification and prevention of meat poisoning]. / De onderkenning en preventie van vleesvergiftigingen.

In this contribution to a series 'Papers of Yesterday and Today' a retrospective review of developments in the identification and control of meat 'poisoning' defined as infections and intoxications following the ingestion of bacteriologically unsound meat and meat products is presented. Starting from two classical Dutch papers, viz. by H. J. H. Stempel (1891) and K. Hoefnagel (1899) illustrating the knowledge of meat 'poisoning' acquired in the nineties of the 19th century, developments in the field of bacteriological research on meats and the resulting efforts to manage meat 'poisoning' are summarised. Attention is paid to the role of Dutch veterinarians in investigations on the aetiology of meat infections resulting in the adoption of legal meat inspection in 1922 and the ensuing reduction in the occurrence of mass outbreaks of meat poisoning. However, despite marked improvement of the standard of hygiene in the food industry in general and expert monitoring of meat production lines by veterinarians in particular, infections and intoxications transmitted by meat and meat products are still quite prevalent. Essentially, their management can only be achieved by strict adherence to Good Manufacturing Practices (GMP) throughout animal husbandry, slaughter, distribution and storage, termed longitudinally integrated safety assurance. Professional monitoring by an up-to-date meat inspection system, however, continues to be indispensable in the prevention of food-borne infections and intoxications. Some recommendations are made for effective intervention in the infection cycle of food-transmitted pathogens originating from the high infection pressure on slaughter lines, resulting from contamination acquired at previous stages of the animal production chain.

Histometric and chemical methods for determining collagen in meats.

In this paper we discuss the advantages and disadvantages of using histometric and chemical methods for detecting collagenous connective tissue in meat products. Twelve samples of different kinds of smoked sausage meat of known recipe were examined chemically and by two histometric procedures. The results obtained with the histometric procedures were almost identical (r = .96) and there was a strong correlation (r = .88) between the results of one histometric procedure and those obtained with the chemical method. It is concluded that histometric and chemical testing methods are equally valuable in that they both provide an objective quality judgement of the meat under investigation. However, since both methods have certain drawbacks and involve certain errors they should be used in conjunction with each other and not independently. In this way it should be possible to obtain a more complete picture of the composition and/or quality of meats than that obtained via chemical analysis alone.

[Histometric study of meat products. A literature review]. / Histometrisch onderzoek van vleeswaren. Een literatuuroverzicht.

In the present paper, the literature on the development of methods for histometric monitoring the quality of meats is reviewed. The value of specific techniques, statistical interpretation of results and the practicability of automation of histometric analysis are examined more closely. It is concluded from the study of the literature that histometric examination of meats allows an objective assessment of volume percentages of tissue components. When a distinct difference in contrast between various tissues is achieved by specific staining methods, developments in the field of image analysis systems will allow automation of the quantitative histological examination of meats.

Tissue composition of mechanically deboned pork (MDP).

The tissue composition of the mechanically deboned pork produced by a discontinuous pressure system was investigated. By means of quantitative microscopy volume ratios (in terms of volume in volume fractions) of striated muscle, collagenous and elastic connective tissue, bone and cartilage in homogenized samples from eight different producers were determined. Crude protein, fat, calcium and the hard bone residue were determined chemically. In addition, we measured the size of the hard bone particles. The muscle/connective tissue ratio varied from 0·3 to 6·9. The hard bone residue, determined by means of the KOH-method, varied from 0·05 to 0·62%. 0·6% of the bone particles were larger than 3 mm. In addition to chemical analysis we regard quantitative microscopy for the determination of the tissue composition of mechanically deboned pork as imperative for quality control.

[Keeping qualities of bovine udders (author's transl)]. / Houdbaarheid van runderuiers.

Three trials were made, in which mammary tissues obtained under hygienic conditions were stored together with discharged milk at 4 degrees and 20 degrees C. Bacteriological, histological, organoleptic and pH studies were done to assess the keeping qualities and spoilage of these tissues. The results of these studies showed that mammary tissues stored at 4 degrees C together with discharged milk will remain stable for a maximum period of four days. Inadequate chilling or failure to chill (as is often the case on storage in receptacles in the field) is inadmissible because of spoilage (one day) and the rapid growth of Staphylococcus aureus. The discharged milk stored along with the mammary tissues will have an adverse effect on the keeping qualities of the tissues. Spoilage of mammary tissues may occur as well in the superficial layer as in the deeper layers as both the surface and the subjacent tissues harbour bacteria. Penetration of bacteria from the surface to the deeper tissues does not occur. The paper concludes with recommendations based on previous studies and above mentioned investigation regarding good manufacturing practices where the production, storage and treatment of bovine udders are concerned.