Prevalence of verotoxigenic Escherichia coli O157 (VTEC O157) and compliance with microbiological safety standards in bovine carcasses from an industrial beef slaughter plant

The presence of Salmonella spp. and levels of Enterobacteriaceae and aerobic plate count were determined in 300 bovine carcasses randomly collected in an industrial cattle slaughterhouse in Catalonia (Spain) as part of a control programme to validate good slaughter practices according to Commission Regulation No 2073/2005. The verotoxigenic Escherichia coli O157 (VTEC O157), although not currently legislated, was also investigated in the same carcasses due to the importance of bovines as a reservoir for this micro‐organism. Virulence genes (vtx1, vtx2 and eae), the presence of fliC_H7 and antimicrobial susceptibility were studied in E. coli O157 isolates. Levels of Enterobacteriaceae and aerobic colonies and the presence of Salmonella were within the admissible range stipulated by current legislation. However, VTEC O157 was detected in 14·7% of carcasses. Among the VTEC O157 strains tested for antimicrobial susceptibility, 65% were multiresistant. Overall, the results of this study indicate that even with good manufacturing practices, contamination with VTEC O157 can occur and cattle meat can pose a risk to human health. These results confirm the need for a review of the appropriateness of introducing antimicrobial treatments in the processing of cattle carcasses in Europe.

Significance and Impact of the Study

This study describes the prevalence of verotoxigenic and multidrug‐resistant E. coli O157 strains in bovine carcasses. These results suggest that despite the good manufacturing practices used in the slaughterhouse studied (the largest in Catalonia slaughtering over 81 000 cattle per year), the absence of verotoxigenic E. coli O157 in bovine carcasses cannot be guaranteed.     

High-pressure processing – effects on microbial food safety and food quality

High-pressure processing (HPP) is a nonthermal process capable of inactivating and eliminating pathogenic and food spoilage microorganisms. This novel technology has enormous potential in the food industry, controlling food spoilage, improving food safety and extending product shelf life while retaining the characteristics of fresh, preservative-free, minimally processed foods. As with other food processing methods, such as thermal processing, HPP has somewhat limited applications as it cannot be universally applied to all food types, such as some dairy and animal products and shelf-stable low-acid foods. Herein, we discuss the effects of high-pressure processing on microbial food safety and, to a lesser degree, food quality.     

Quantifying the relative contribution of ante- and post-mortem factors to the variability in beef texture

This study aims to investigate the relative contribution of ante- and post-mortem factors to the final quality of beef. In all, 112 steers (four breed-crosses) were arranged in a 2 × 2 × 2 factorial experimental including production system, growth implant and β-adrenergic agonist strategies. Carcasses were suspended by the Achilles tendon or the aitch bone and meat was aged for 2/6/13/21/27 days (longissimus muscle) or 2/27 days (semimembranosus muscle). Meat quality traits related to beef texture were measured. Statistical analyses were developed including ante- and post-mortem factors and their relative contribution to the variability observed for each measured trait was calculated. The main factor responsible for the variability in sarcomere length was the suspension method (91.1%), which also influenced drip-loss (44.3%). Increasing the percentage of British breeds increased (P < 0.05) the intramuscular fat content in longissimus muscle, but only when implants were not used. Thus, the breed-cross, implant strategy and their interaction were responsible for >58% of the variability in this trait. The variability in instrumental and sensory tenderness was mainly affected by post-mortem factors (carcass suspension, ageing time and their interaction), explaining generally ∼70% of the variability in these traits. Breed-cross was the second most important effect (∼15%) when carcass suspension was not considered in the model, but still ageing time was responsible for a much larger proportion of the variability in tenderness (>45%). In conclusion, post-mortem handling of the carcasses may be much more effective in controlling beef tenderness than pre-mortem strategies.     

Relationships between the density of different indicator organisms on sheep and beef carcasses and in frozen beef and sheep meat

AIM: To describe the relationship between the concentration of different indicator bacteria in red meat. METHODS AND RESULTS: Enumeration data for aerobic plate count (APC), Enterobacteriaceae, coliforms and Escherichia coli biotype I were analysed from an Australia-wide survey of beef carcasses, sheep carcasses, frozen beef and frozen sheep meat. In all commodities, there was only low-to-moderate rank correlation (0.16-0.47) between concentration of APC and concentration of each Gram-negative indicator. Rank correlations between counts of Gram-negative indicators were much higher (0.47-0.92) especially when nondetections were excluded from analysis (0.78-0.94). Receiver-operator characteristics analysis showed that detection of coliforms can predict the presence of E. coli biotype I with almost 100% sensitivity but fails to predict absence in 2.7-8.5% of samples not containing E. coli biotype I. CONCLUSIONS: Enumeration of coliforms is a useful adjunct to enumeration of E. coli biotype I or Enterobacteriaceae in red meat. The density of coliforms or Enterobacteriaceae can be used to predict the presence or absence of E. coli biotype I, although when the latter is at low prevalence errors in positive test prediction can be large. SIGNIFICANCE AND IMPACT OF THE STUDY: A quantitative basis is provided for comparing the concentration of different indicator bacteria measured in the production, regulation and trade of red meat.     

Production of propionic acid by microbiological way. Part 2. Effect of the pH value on cell growth and acid production

The batch propionic acid fermentation of sugar cane molasses by Propionibacterium acidi propionici PP-1 was studied at various pH values ranging from 5 to 7. The optimum pH range for cell growth was between 6 and 7, whereas the specific growth rate decreased with the pH in the acidic range down to 0.197 h^?1 at pH 5. The propionic acid yield increased with decreasing pH; it changed from 22% (wt/wt) at pH 7 to 38% at pH 5. It has been obvious that this process is inhibited by the products of the fermentation and more severely in the acidic range where the acids are in an unionized state. A generalized equation of the non-competetive inhibition was adjusted for each pH value, and kinetic inhibition constants were estimated.     

Applications of nonthermal plasma technology on safety and quality of dried food ingredients

Cold plasma technology is an efficient, environmental-friendly, economic and noninvasive technology; and in recent years these advantages placed this novel technology at the centre of diverse studies for food industry applications. Dried food ingredients including spices, herbs, powders and seeds are an important part of the human diet; and the growing demands of consumers for higher quality and safe food products have led to increased research into alternative decontamination methods. Numerous studies have investigated the effect of nonthermal plasma on dried food ingredients for food safety and quality purposes. This review provides critical review on potential of cold plasma for disinfection of dried food surfaces (spices, herbs and seeds), improvement of functional and rheological properties of dried ingredients (powders, proteins and starches). The review further highlights the benefits of plasma treatment for enhancement of seeds performance and germination yield which could be applied in agricultural sector in near future. Different studies applying plasma technology for control of pathogens and spoilage micro-organisms and modification of food quality and germination of dried food products followed by benefits and current challenges are presented. However, more systemic research needs to be addressed for successful adoption of this technology in food industry.     

System expansion and allocation in life cycle assessment of milk and beef production

Background, Goal and Scope  System expansion is a method used to avoid co-product allocation. Up to this point in time it has seldom been used in LCA studies of food products, although food production systems often are characterised by closely interlinked sub-systems. One of the most important allocation problems that occurs in LCAs of agricultural products is the question of how to handle the co-product beef from milk production since almost half of the beef production in the EU is derived from co-products from the dairy sector. The purpose of this paper is to compare different methods of handling co-products when dividing the environmental burden of the milk production system between milk and the co-products meat and surplus calves. Main Features  This article presents results from an LCA of organic milk production in which different methods of handling the co-products are examined. The comparison of different methods of co-product handling is based on a Swedish LCA case study of milk production where economic allocation between milk and meat was initially used. Allocation of the co-products meat and surplus calves was avoided by expanding the milk system. LCA data were collected from another case study where the alternative way of producing meat was analysed, i.e. using a beef cow that produces one calf per annum to be raised for one and a half year. The LCA of beef production was included in the milk system. A discussion is conducted focussing on the importance of modelling and analysing milk and beef production in an integrated way when foreseeing and planning the environmental consequences of manipulating milk and beef production systems. Results  This study shows that economic allocation between milk and beef favours the product beef. When system expansion is performed, the environmental benefits of milk production due to its co-products of surplus calves and meat become obvious. This is especially connected to the impact categories that describe the potential environmental burden of biogenic emissions such as methane and ammonia and nitrogen losses due to land use and its fertilising. The reason for this is that beef production in combination with milk can be carried out with fewer animals than in sole beef production systems. Conclusion, Recommendation and Perspective  Milk and beef production systems are closely connected. Changes in milk production systems will cause alterations in beef production systems. It is concluded that in prospective LCA studies, system expansion should be performed to obtain adequate information of the environmental consequences of manipulating production systems that are interlinked to each other.     

A preliminary study on the quality and safety of milk in donkeys positive for Toxoplasma gondii

Toxoplasmosis is one of the five parasitic diseases considered as a priority for public health action. The consumption of raw milk products represents a possible risk, in particular for certain categories of people. The aim of this study was to evaluate the possible effects of Toxoplasma gondii on milk yield and quality in sero-positive animals with parasitemia. Eighteen healthy lactating Amiata jennies, between 90 and 180 days were included in the study. Four donkeys scored positive for immunofluorescent antibody test (IFAT), and each IFAT positive donkey presented parasitic DNA both in the blood and milk. No significant differences were found between milk yield in PCR-positive donkeys compared with the negative cases, however the former tended to have a greater production. Milk quality in the positive donkeys showed a significantly lower percentage of casein (0.72% v. 0.81%) and ash (0.32% v. 0.37%). Positive cases had a highly significant larger average diameter of globules (2.35 µm) and fewer globules/ml (2.39×10⁸). Somatic cell and bacterial counts were normal and in agreement with the literature. Toxoplasma gondii did not seem to present clinical forms in lactating jennies. Further in vivo studies are needed to further assess the risk of T. gondii transmission through donkey milk, together with the impact of different stages of infection on milk quality.     

NADP‐glutamate dehydrogenase activity in nonstarter lactic acid bacteria: effects of temperature,pH and NaCl on enzyme activity and expression

Aims: To screen the glutamate dehydrogenase (GDH) activity of nonstarter lactic acid bacteria (NSLAB) and to determine the effects of temperature, pH and NaCl values used for cheese ripening on enzyme activity and expression of GDH gene. Methods and Results: A subcellular fractionation protocol and specific enzyme assays were used. The effect of temperature, pH and NaCl on enzyme activity was evaluated. The expression of GDH gene was monitored by real‐time PCR. One selected strain was also used as adjunct starter for cheese making to evaluate the catabolism of free amino acids and the production of volatile organic compounds (VOC) during cheese ripening. The cytoplasm fraction of all strains showed in vitro NADP‐dependent GDH activity. NADP‐GDH activity was markedly strain dependent and varied according to the interactions between temperature, pH and NaCl. Lactobacillus plantarum DPPMA49 showed the highest NADP‐GDH activity under temperature, pH and NaCl values found during cheese ripening. RT‐PCR analysis revealed that GDH expression of Lact. plantarum DPPMA49 was down‐expressed by low temperature (<13°C) and over‐expressed by NaCl (1·87–5·62%). According to NADP‐GDH activity, the highest level of VOC (alcohols, aldehydes, miscellaneous and carboxylic acids) was found in cheeses made with DPPMA49. Conclusions: The results of this study may be considered as an example of the influence of temperature, pH and NaCl on enzyme activity and expression of functional genes, such as GDH, in cheese‐related bacteria. Significance and Impact of the Study: It focuses on the phenotypic and molecular characterization of the NADP‐GDH in lactobacilli under cheese‐ripening conditions. The findings of this study contribute to the knowledge about enzymes involved in the catabolism of amino acids, to be used as an important selection trait for cheese strains.     

水培条件下pH值对柳枝稷幼苗生长发育的影响

土壤的p H值是限制植物生长发育的一个关键因素。柳枝稷是一种可作为牧草,水土保持的多年生C4能源植物。试验在水培条件下,利用裂区试验设计,以柳枝稷品种(系)为主区,水培液p H值为副区,对反映柳枝稷幼苗生长发育状况的指标进行统计分析。结果显示,随水培液p H值的酸碱强度增大,柳枝稷不同品种(系)幼苗的分蘖数、株高、苗鲜重、根冠比、根系活力以及净光合速率都极显著降低(P0.01),而幼苗保护酶活性以及丙二醛(MDA)含量则极显著升高(P0.01)。尤其是当PH值低于5.0时,幼苗的受到的胁迫更为明显,幼苗超氧化物歧化酶(SOD)和过氧化物酶(POD)活性反而急剧下降。与酸胁迫(p H值7.0)相比,柳枝稷对碱胁迫(p H值7.0)的适应能力更强,其中以西稷2号的抗逆性表现最好。因此应用柳枝稷在边际土壤地区推广种植时,要尽量避免强酸性土壤(p H值5.0),且选用西稷2号品系较为适宜。     

The origins of agriculture in the Americas

Three independent centers of domestication and agricultural origin have been identified in the Americas: the south-central Andes, Mexico, and most recently, eastern North America. Much of the evidence for early domesticates in these three regions has been excavated from higher elevation dry caves and rock shelters. These sites contain remarkably well preserved plant and animal remains, along with a record of short-term occupation by small groups of hunter-gatherers and early cultivators. As a result it has long been thought that plants and animals were brought under domestication in the Americas by small, seasonally mobile societies living in upland settings. The age of small seeds and other plant materials recovered from such dry caves and believed to represent early domesticates was, of necessity, determined indirectly, through conventional large-sample radiocarbon dating of organic material thought to be contemporaneous. In each of the three regions, the earliest domesticates were believed to date between 7,000 and 10,000 B.P. The origin of agriculture in the Americas was thought to be roughly contemporary with the transition from foraging to farming in the Near East (Fertile Crescent, ca. 10,000 B.P.) and China (Yangtze Corridor, ca. 8,500 B.P.). Since the mid-1980s, however, the age of many of the proposed early domesticates in the Americas, as well as their contexts of domestication, have been re-examined, beginning in eastern North America. The excavation of larger and more sedentary river valley settlements in eastern North America has yielded ample evidence of the cultivation of domesticated seed plants. This evidence is as old as or older than that recovered from seasonally occupied upland caves and rock shelters. In addition, a new and more rigorous standard for evidence of domestication has been adopted in eastern North America. That standard, which requires direct dating of seeds and other plant parts that exhibit clear, unequivocal, and well-documented morphological markers of domestication, is now being applied throughout the Americas, producing conservative timetables of domestication and agricultural origins that contradict alternative, more speculative chronological frameworks. Under the new standard of evidence, domestication of plants in all three independent centers (and in the Andes, domestication of animals) appears to have taken place between about 5,500 and 4,000 years ago, much more recently than previously was thought. Several lines of evidence also suggest that the Native American societies that first brought these species under domestication may not have been exclusively seasonally mobile hunter-gatherers of higher-elevation environments. In each of the three regions, domesticates recovered from upland caves may reflect a transition to a farming way of life accomplished by societies occupying more sedentary settlements in river valleys. In some cases, upland caves containing domesticates may represent one component in the seasonal round of early food production by societies occupying nearby river valleys; in others, they may mark the subsequent expansion of food production economies out of rich river valley resource zones into adjacent upland environments.     

Effect of the inclusion of food waste in pig diets on growth performance, carcass and meat quality

Food waste from fish and fruit shops was used as an alternative to the grain in grower-finisher pig diets. Two diets were formulated on an iso-nutrient basis (14 MJ digestible energy per kg, 160 g crude protein per kg on a dry-matter basis) to contain 0 g of food waste per kg in the control diet and 50 g of fish-shop waste per kg and 120 g of fruit-shop waste per kg in the experimental diet. In the study, 28 pigs per diet (seven pigs per pen) were fed ad libitum from 20 kg to 100 kg, then, they were slaughtered and the carcass characteristics determined. The inclusion of food waste in the diet had no significant effect (P>0.05) on average daily feed intake (2.12 v. 2.20 kg/day), average daily gain (0.74 v. 0.78 kg/day), or gain/feed (0.35 v. 0.35 kg per kg). In the case of the experimental diet, backfat thickness was significantly lower (18.0 v. 21.3 mm, P < 0.01). The results of the taste test indicated that the meat from food waste-fed pigs had acceptable organoleptic quality although a very light aroma to fish was observed in the bacon (P < 0.01).It was concluded that food waste from the fish and fruit shops could be included in grower-finisher pig diets without any detrimental effect on growth performance and only minor effects on carcass characteristics and meat quality.