Evaluation of enhanced haemolysis agar for detection of Listeria spp. and L. monocytogenes from production lines of fresh to cold-smoked fish

Enhanced haemolysis agar (EHA) was compared to the two conventional Listeria isolation agars Oxford and PALCAM for its ability to detect Listeria spp. from production lines of fresh to cold-smoked fish. The ability of EHA for distinguishing L. monocytogenes colonies from other Listeria spp. was also evaluated. A total of 243 fish and environmental samples were analysed. Overall, 42 samples were found to contain Listeria spp. Only 34 samples were positive simultaneously by the three plating media. Two samples considered to be negative by the two conventional agars were found to be positive after isolation on EHA. All three selective agars were shown to be less effective in recovering Listeria spp. after primary enrichment in half-Fraser broth, compared to secondary enrichment in Fraser broth after 24 and 48 h. From 79 Listeria but presumptive negative L. monocytogenes colonies, EHA identified correctly 76 Listeria spp. and presented three false-negative results_three colonies further identified as L. monocytogenes but showing no noticeable haemolysis on EHA. Twenty-three of the thirty-three L. monocytogenes presumptive positive colonies, were confirmed positive and ten were identified as L. seeligeri. Despite its ability of distinguishing L. monocytogenes from the other Listeria spp., unless it is produced as a commercial medium, EHA cannot be an alternative to time-consuming classical identification because the preparation of this medium is both time and labour intensive

Evaluation of mini-VIDAS rapid test for detection of Listeria monocytogenes from production lines of fresh to cold-smoked fish

This study was conducted to evaluate the efficacy of the mini-VIDAS Listeria monocytogenes (LMO) system (BioMe´rieux Vitek, Inc., Missouri, USA) for detection of L. monocytogenes in environmental and fish samples from three Portuguese cold-smoking plants and from their fresh fish suppliers. Mini-VIDAS-LMO is a fully automated system that uses fluorescent ELFA (Enzyme Linked Fluorescent Assay) technology for detection of Listeria monocytogenes antigens in food. It can be a rapid screening method alternative to time consuming classical isolation and identification. Two hundred and ninety five samples were tested in mini-VIDAS-LMO and in parallel by the ISO 11290-1 traditional protocol. The mini-VIDAS-LMO detected 8 of the 11 confirmed positive samples and presented 11 false positive results. The specificity of the mini-VIDASLMO found in this experiment was 0.96 and the sensitivity 0.7

Efficiency of four secondary enrichment protocols in differentiation and isolation of Listeria spp. and Listeria monocytogenes from smoked fish processing chains

Four secondary enrichment protocols (conventional methods: UVM II, Fraser 24 h and Fraser 48 h: Impedimetric method: Listeria electrical detection medium) were studied for their ability to isolate Listeria spp. and Listeria monocytogenes from fish and environmental samples collected along the processing chain of cold-smoked fish. From all methods, Listeria spp. and L. monocytogenes were respectively present in 56 and 34 of 315 samples analysed. Fraser broth incubated for 48 h gave the fewest false negative Listeria spp. results [4/56; (7.1%)], but concurrently only 15/34 (44.1%) samples were correctly identified as containing L. monocytogenes. Listeria electrical detection (LED) medium detected only 36/56 (64.3%) Listeria spp. positive samples. Despite this lower isolation rate, LED identified 20/34 (58.8%) L. monocytogenes positive samples correctly and gave fewer false positive results. The overall conclusion was that more than one isolation method is needed to accurately estimate L. monocytogenes contamination rates

Rice Bran Stabilisation and Oil Extraction Using the Microwave-Assisted Method and Its Effects on GABA and Gamma-Oryzanol Compounds

RICEPLUS - POCI-01-0247-FEDER-033389 2020.09555BDRice bran oil (RBO) is a valuable ingredient extracted from rice bran (RB), a side stream of polishing rice grain in the milling process. RBO is rich in bioactive ingredients with potential health benefits, such as gamma-oryzanol (GO) and gamma-aminobutyric acid (GABA). Despite its benefits, the quality of RBO depends on the degree of stabilisation of the RB, which is easily affected by lipase enzymes, and thus needs an effective treatment prior to RBO production. To assess the potential of the microwave-assisted method for RB stabilisation and RBO extraction, three Carolino rice varieties (Ariete, Teti, Luna) were tested. The effect of RB stabilisation was evaluated via acid value, water absorption, and GO and GABA levels. The RBO yield was optimised by solvent, temperature, and solvent-to-sample ratio, and the GO and fatty acid levels were determined. The RB stabilisation for the Luna variety did not affect the GO and GABA; for the Ariete and Teti varieties, the GO decreased by 34.4% and 24.2%, and the GABA increased by 26.5% and 47.0%, respectively. The GO levels in RBO samples were not affected by RB stabilisation. The RBO nutritional value was confirmed by the suitable ratio (>2) between polyunsaturated (PUFA) and saturated fatty acids (SFA), with the Teti variety presenting the highest ratio.publishersversionpublishe

Microbiological characterization of fresh cheeses made in Portugal from raw materials to final products

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Monitorização das propriedades de textura, organoléticas e microbiológicas de fiambre de perna de porco fatiado e embalado em atmosfera modificada ao longo do seu tempo de vida

O uso de atmosfera modificada (AM), como técnica de conservação na embalagem de produtos fatiados cárnicos, tem sido uma solução eficaz para assegurar a qualidade do produto e prolongar o respetivo tempo de vida útil, podendo alcançar mercados mais longínquos. Amostras de fiambre da perna extra de porco, foram embaladas com uma mistura de gás com 30% de CO2 e 70% de N2, em bandejas termoformadas de APET/EVOH/PE e seladas com filme PE/PVDC. Ao longo de 35 dias foi monitorizada a evolução da composição da mistura de gases, determinados parâmetros físico-químicos, tais como pH, teor de humidade, parâmetros de cor e textura, propriedades organoléticas e microbiológicas. O fiambre foi também avaliado sensorialmente, através de uma análise descritiva quantitativa, em relação ao brilho, cor, aroma, aparência global, flavour, textura (dureza e coesividade) e sabor a sal. Os resultados dos parâmetros físico-químicos não revelaram diferenças significativas ao longo do tempo de armazenamento , com a excepção de alterações na intensidade da cor e ligeiras alterações de textura. O painel detetou diferenças entre produtos frescos e os tempo s mais tardios de armazenamento. Não foram detetad os microrganismos patogénicos em nenhuma das amostras analisadas.Projecto n.º 38869 EXTRASLICED45, co - financiado pelo FEDER através do COMPETE - POFC, no âmbito do QREN 2007 - 201

Comparison of milk from two different cow breeds Barrosã and Frísia

Milk from two different cow breeds, Barrosã and Frísia, was studied. Within the same breed five and four milk samples were taken respectively for chemical and microbiological analysis. The following chemical parameters were analysed in triplicate: Total Fat, Fatty Acids Identification and Quantification, Protein, Casein, Albumin, Non-protein Nitrogen, Vitamin A, Vitamin D, Phosphorus, Potassium, Sodium, Iron, Magnesium, Calcium, Ash, Total solids, Lactic acid and Acidity. In general terms milk from Barrosã breed showed higher values for all analysed parameters except for Total Fat, Total Solids and Vitamin D. Statistical analysis, by testing the chemical parameters all together using the Hotelling T2 test showed that milk samples from the two cow breeds were significantly different (α=0,05). Microbiological analysis (Total Viable Counts (30ºC), Escherichia coli, Staphylococcus coagulase + and Listeria monocytogenes) was also performed. Staphylococcus coagulase + was found in one milk sample from Barrosã breed. Listeria monocytogenes was found in two milk samples from Frísia breed

Sensory evaluation of meat from entire male pigs raised with different feeding and housing conditions

Introduction: Boar taint is an off-odour/off-flavour found in meat from entire male pigs due to two main compounds: androstenone and skatole. The incidence of boar taint is of concern when considering the use of entire males for pork meat production. Objectives: This study aims at evaluating sensory characteristics of meat from entire male pigs raised under specific conditions in order to reduce or eliminate the boar taint. Methods: Belly meat from entire male pigs raised under six different conditions (normal housing versus improved housing) and feeding with different levels of added inulin (0%, 3% and 6%) was analysed. A Quantitative Descriptive Analysis (QDA®) methodology was applied to samples, previously cooked and presented in closed jars, and the panel, composed by 10 trained panellists, was asked to assess odour and flavour of skatole and androstenone, texture and sweet flavour. Results: Significant differences (p<0.05) were found between samples concerning skatole and androstenone odour and flavour, and texture compared to control samples. Conclusions: As expected, the boar taint was stronger in samples where no addition of inulin and no improved conditions were applied. It can be concluded that the inulin addition into pig feed have positive effects when conjugated with better housing conditions.info:eu-repo/semantics/publishedVersio

Anti-hypertensive activity of horse mackerel pulverized with three different extracts from marine origin

Hypertension is a serious risk factor and the most prevalent trigger to fatal cardiovascular diseases such as stroke and myocardial infarction. The marine environment is a unique source of molecules with biological activity such as antioxidant, anti-coagulant and anti-hypertensive activities. In this study, the anti-hypertensive activity of horse mackerel fillets (HMF) pulverized with each of the following marine extracts (derived from enzymatic hydrolysis) were determined: microalgae (Tetraselmis sp. incubated with subtilisin and cellulase), Mussel_Sub (Mytilus galloprovincialis minced and incubated with subtilisin protease) and Mussel_ Pro+Alc (Mytilus galloprovincialis boiled and incubated with Protamex and Alcalase). Horse mackerel fillets were evenly sprayed with each extract and frozen until subsequent analyses. Non-sprayed HMF were used as control. Aqueous extracts were prepared from HMF by sonication. Anti-hypertensive activity was determined by the angiotensin I-converting enzyme (ACE) inhibitory activity method. Data are presented in Table.1 as average±standard deviation of two replicates. Table 1. Anti-hypertensive activity of Horse Mackerel fillets sprayed with Extracts from Marine Origin. Horse mackerel fillet showed by itself an interesting anti-hypertensive profile. Notwithstanding, the tested marine-derived extracts effectively increased its biological potential(up to four-fold), with the best anti-hypertensive profile being achieved with microalgae and Mussel_Pro+Alc extracts. These extracts have an enormous potential to be used in the development of innovative food products that emphasize functionality, convenience, nutrition and health – goal of the project VALORMAR (POCI-024517-FEDER)(PPS1).info:eu-repo/semantics/publishedVersio

Extracts from marine origin as functional ingredients to improve the antioxidant activity of horse mackerel (trachurus trachurus)

Marine species have been largely described as a source of antioxidant extracts. The production of antioxidant extracts from microalgae and mussels may be an interesting sustainable approach for food industry, since microalgae are easy to produce, and mussel’s commercialization generates losses and waste. Thus, this work studied the effect of three marine extracts, produced from Tetraselmis sp. and Mytilus galloprovincialis, on the antioxidant activity of Horse Mackerel fillets (HMF), with the goal of developing functional ingredients for food industry. Three extracts were produced by enzymatic hydrolysis: Tetraselmis (cellulase and subtilisin), Mussel_Sub (subtilisin) and Mussel_ Pro+Alc (Protamex and Alcalase). All the extracts were ultra-filtrated using a 3KDa cut-off. HMF were evenly sprayed with each extract, and a control without extract was used. Aqueous extracts were prepared from HMF by sonication. The antioxidant activity was determined by ORAC and ABTS assays. The results obtained for the ORAC were 15.2±3.0, 45.2±1.8, 37.6±2.6 and 20±5.0 μM Trolox Equivalent (TE)/g of sample, and the ABTS activity was 6.5±0.2, 12.9±0.6, 8.5±0.1, and 14.0±0.4 μM TE/g of sample for control, Tetraselmis, Mussel_Sub and Mussel_Pro+Alc, respectively. Fillet sprayed with Tetraselmis extract presented statistically significant differences for ORAC and ABTS results (three and two-fold), and Mussel_Pro+Alc for ABTS results (two-fold), when compared to control fillets (pThe marine extracts application enhanced the antioxidant activity of the HMF, with Tetraselmis extract showing the higher potential in both antioxidant assays, thus it may be promising as an ingredient for the development of functional food aiming preservation properties as well as health promotion.info:eu-repo/semantics/publishedVersio