Genotype- by-environment interaction for marketable tuber yield in advanced potato clones using AMMI and GGE methods

Analysis of genotype-by-environment interaction (GEI) is critical in the local potato breeding and selection programme to obtain information on the performance of the genotypes for yield adaptability and stability. The objective of this study was to assess the marketable tuber yield of 18 advanced potato clones compared to the commercial variety Spunta at four locations (Bigara, Réduit, St. Antoine and Rivière du Poste), representative of four major soil types in Mauritius. They were analysed for adaptability and stability using the additive main effects and multiplicative interaction (AMMI) model and genotype main effect and genotype x environment interaction (GGE) biplot. Five clones gave significantly the highest marketable tuber yield in terms of overall ranking with yield increase of 47.4% to 59.6% over the control variety Spunta. AMMI analysis of variance detected significantly (P < 0.001) higher proportion of variation in marketable tuber yield due to environment (42%); followed by genotype x environment interaction (21%) which justified multi-locational testing. AMMI1 biplot demarcated clones 142/161/2 and 142/161/5 as high yielding and most stable while AMMI 2 biplot identified the winning genotypes for a specific environment. Thus, clones142/161/4 and 161/142/16 had specific adaptation to Bigara, 29/5/2 and 21/5/3 were adapted to St. Antoine, 21/5/10 to Rivière du Poste whereas 29/5/3 was adapted to Réduit. The GGE biplots identified clones 142/161/2 and 142/161/5 as the two most desirable genotypes close to the “ideal genotype”. The “which- won- where” view of the GGE biplot further pointed to the presence of two mega-environments, which corresponded to the sub-humid irrigated/humid environments (Réduit, St. Antoine and Rivière du Poste) and the high altitude super-humid environment (Bigara). These results showed that in future both AMMI and GGE methods can be integrated in the local potato breeding programme to select superior genotypes through multi-year and multi-locational yield evaluation. &nbsp

Development of dry-cured sausages using spent-hen meat: manufacturing practices and product physical, chemical and microbiological quality

Laying hens that complete their egg production cycle in one year constitute one important by-product of the egg industry. They are referred to as spent-egg laying hens, spent layers, or spent hens. Locally, the meat of these spent hens is mainly sold on the fresh market and fetches a significantly lower price than fresh broiler meat. One of the avenues to improve the utiliza­tion of spent-hen meat is to process it into higher value-added products that are palatable and reasonable in cost. The food processing technique that has been chosen is fermentation and drying to produce dry-cured fermented sausages. The research hypotheses were as follows: the meat, skin and abdominal fat of spent-hen meat are technologically suitable for making dry-cured sausages; fermentation/drying can lead to a safe, shelf-stable and quality poultry sausage. Thus, this study was conducted to develop and evaluate a fermented/dried 100-per­cent-poultry sausage made from spent-layer meat and fat. Sausages were prepared using ground meat (breast, thigh and drumstick), skin, and abdominal fat at 10, 15 and 25% levels, salt, sodium nitrite, garlic, and glucose. The mix was inoculated with Lactobacillus plantarum at a rate of ~5.0 log10 colony-forming units (CFU/g). The sausages were stuffed in non-edible cellulose casings. They were dried at 30°C and 85% relative humidity for 15 days, and sampled at 0, 3, 6, 9, 12 and 15 days for analysis of protein and fat contents, color, pH, water activity, total viable count, Salmonella spp., Staphylococcus spp., and L. plantarum counts. Each treatment (25 sausages) was replicated three times. Irrespective of fat levels, pH sharply declined in all batches from an initial value of 6.0–6.3, to 5.3 at day 3, and finally to 4.8–4.9 at day 15 of drying. The average initial moisture content of the sausages was 70% (wet basis). It decreased gradually during the fermentation/drying period to about 51–53% on day 6, and 35% on day 15, irrespective of fat levels. All experimental batches showed similar mass loss over drying time. Mass loss was more pronounced during the first six days (50–55%) and was mainly attributed to moisture loss, as fat drip losses were negligible. Water activity gradually declined from an initial value of 0.97 to 0.71 for the three fat levels. The sausage color changed to reddish brown as from day 3. This translated in decreasing L* (lightness) and positive b* (yellowness) values, and increasing positive a* (redness) values (Figure 1 and Table I). No Salmonella was detected in any samples analyzed. Counts of Staphylococcus spp. were high with 104/g to 108/g at the end of the fermentation/drying period. L. plantarum counts increasedduring the first five days of fermentation from 4.9 to 8.7 log10 CFU/g and remained practically at this level for the rest of the drying period. There was unwanted mould growth on the cel­lulose casings as from day 3. In all cases, the sausages lacked the compactness typical of dry-cured sausages. The meat and fat particles in the final sausages were not uniformly distributed. This may be due to the low melting point of the fat thereby caus­ing smearing of fat particles. Overall, the potential of using spent-layer meat for the manu­facture of dry-fermented sausage was shown to be technologi­cally feasible. However there is a need to optimize the process­ing steps, especially with regard to the starter culture, and the temperature and relative humidity of fermentation/drying, to improve the safety and quality of the sausages

Traditional processing of pork meat in Rodrigues island: processing techniques and product quality

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Prevalence of Shiga-toxigenic <em>Escherichia coli</em> in Mauritian dairy cattle

Shiga-toxigenic Escherichia coli (STEC) are important human pathogens (1). They are characterized by their ability to pro­duce Shiga toxins (stx1 and stx2). Seven STEC have been shown to withstand food processing procedures that are expected to ensure food safety. Clinical symptoms associated with STEC infection can vary from abdominal cramps and acute bloody diarrhea to more severe aftereffects including hemorrhagic coli­tis, hemolytic uremic syndrome and thrombocytopenic purpura, which can lead to kidney failure and death. Dairy cattle, which excrete STEC in their feces, are a major source of STEC infection (2). Humans become infected with STEC through direct contact with infected animals or by inges­tion of contaminated water, raw and unpasteurized milk, meat products, and/or plant-derived products (4–6). The objectives of this study were to estimate both cow-level and farm-level point prevalence estimates of STEC fecal shedding in Mauritian dairy cattle and to characterize putative STEC isolates based on their virulence factors. A cross-sectional study was conducted to investigate the preva­lence of STEC in the dairy cattle population of Mauritius. Fecal samples were collected from 150 individual dairy cattle from 38 dairy farms located throughout the nine district regions of the island. Collected samples were enriched in modified Tryptic Soy broth followed by isolation on CHROMagarTM STEC (3). Suspected isolates were streaked onto EMB agar, further puri­fied on nutrient agar and subsequently cryopreserved in glyc­erol until further investigation. Putative isolates were charac­terized using molecular techniques (7, 8) for the presence of chromosomal sequences encoding Shiga toxin genes (stx1 and stx2), the intimin protein (eaeA) and the plasmid-encoded hemo­lysin (hlyA). Out of the 38 farm samples, 29 farms (76%) were found to be positive for presumptive STEC isolates. From the 150 fecal samples collected, 111 (74%) were found to harbor presump­tive STEC isolates (Table I). Polymerase-chain-reaction- (PCR-) based characterization has confirmed the presence of STEC in a number of fecal samples. Results obtained so far indicate that STEC are common members of the gut microbiome of dairy cattle in Mauritius. Presumptive STEC isolates are currently being screened with PCR targeting stx1, stx2, eaeA and hlyA genes. This epidemiological study on STEC is the first of its kind in Mauritius and in the Indian Ocean region. It aims at providing new information concerning the presence of STEC in Mauritian dairy cattle. It involves the use of the latest chromogenic agar (CHROMagarTM STEC) available on the market. This culture medium has been designed for the detection of a wide range of STEC from different sources. The study highlights the importance of implementing proper sanitary measures at the dairy farm level to prevent cross contamination of milk and the surrounding environment

Microbiological and physico-chemical characterization of the Rodriguan chinese sausage

Rodrigues Island is a dependency of the Republic of Mauritius and is located at about 653 km northeast of it. Pig fattening is an important livestock activity in Rodrigues and pork is the most widely consumed meat (1). It is reported that Rodriguan pork has special sensorial attributes, firstly because pigs are fed with traditional starchy crops such as cassava, banana and sweet potato, and kitchen wastes, and secondly because of the rearing method which is mainly an outdoor system. In a previous study (2), the range of processed products made from pork and their processing techniques were described. The Rodriguan chinese sausage, a traditional dry-cured pork-based product, is one of the most popular products and is considered as an authentic product of Rodrigues (Figure 1). It could be eventually promoted and marketed with an appellation such as the geographical indi­cation label. However, from a food safety standpoint, there is a lack of information on the microbiological and physico-chemical characteristics of the finished product. The main objective of this work was to determine the microbio­logical and physico-chemical characteristics of the Rodriguan chinese sausage with a view to establish the standard profile of the product. The study also aimed to identify weaknesses and make recommendations to improve safety, quality and shelf life of the product. Sausages were sampled thrice from ten random family-owned processing units in seven villages and retail outlets of Rodrigues from November 2013 to January 2014. At each outlet, two sau­sages were taken and air-transported in sealed plastic bags within two days to the Faculty of Agriculture laboratory for analysis. All analyses were carried out using ISO (International Organization for Standardization) protocols. The total viable count and lactic acid bacteria count ranged from 7.8 to 8.11 and from 7.08 to 7.50 log10 CFUg-1, respectively (Table I). The total coliform and Staphylococcus spp. counts were about 3 log10 CFUg-1 each. Neither Escherichia coli nor Salmonella spp. were detected in the samples analyzed. The water activity, pH and lactic acid content of the sausages fell within the range of values typical of dry-fermented sausages (Table II). However, significant variations between samples were noted with regard moisture, protein, fat and ash contents. Similarly, water activity and pH values showed marked varia­tions between the sausages. In contrast, no significant differences were noted in the L*, a* and b* color attributes as defined by the Commission internationale de l’éclairage (CIE). Results confirmed that the Rodriguan chinese sausage satisfies the criteria of dry-cured raw meat products (3) and is overall a fairly safe and stable product. However, significant variations exist in its physico-chemical and microbiological characteristics probably due to variations in processing by the different artisans. There is thus a need to standardize the processing steps so as to improve the microbiological quality and safety of the sausage

Genomic analysis of sewage from 101 countries reveals global landscape of antimicrobial resistance

Antimicrobial resistance (AMR) is a major threat to global health. Understanding the emergence, evolution, and transmission of individual antibiotic resistance genes (ARGs) is essential to develop sustainable strategies combatting this threat. Here, we use metagenomic sequencing to analyse ARGs in 757 sewage samples from 243 cities in 101 countries, collected from 2016 to 2019. We find regional patterns in resistomes, and these differ between subsets corresponding to drug classes and are partly driven by taxonomic variation. The genetic environments of 49 common ARGs are highly diverse, with most common ARGs carried by multiple distinct genomic contexts globally and sometimes on plasmids. Analysis of flanking sequence revealed ARG-specific patterns of dispersal limitation and global transmission. Our data furthermore suggest certain geographies are more prone to transmission events and should receive additional attention