Phage types, virulence genes and PFGE profiles of Shiga toxin-producing Escherichia coli O157:H7 isolated from raw beef, soft cheese and vegetables in Lima (Peru)

The present study was conducted in Lima Metropolitana to evaluate the prevalence of Shiga toxin-producing Escherichia coli (STEC) O157:H7 in raw beef, raw ground beef, soft cheese and fresh vegetables, sampled at different markets in the city. Between October 2000 and February 2001, 407 food samples were collected from different markets in the 42 districts of Lima Metropolitana. Samples were assayed for E. coli O157 by selective enrichment in modified Tryptic Soy Broth containing novobiocin, followed by immunomagnetic separation (IMS) and plating onto sorbitol MacConkey agar supplemented with cefixime and potassium tellurite. Fifty (12.3%) of 407 food samples resulted positive for E. coli O157 isolation (23 of 102 ground beef; 15 of 102 beef meat; eight of 102 soft cheese and four of 101 fresh vegetables). Thirty-five E. coli O157 isolates were further analysed for the presence of virulence genes. All 35 were positive by PCR for O157 rfbE, fliCh7, eae-gamma1 and ehxA genes. In addition, genes encoding Shiga toxins were detected in 33 of 35 isolates, five isolates (14%) encoded stx(1), stx(2), and 28 (80%) stx2 only. The isolates were of seven different phage types (PT4, PT8, PT14, PT21, PT34, PT54, and PT87) with three phage types accounting for 80% of isolates: PT4 (15 isolates), PT14 (8 isolates), and PT21 (5 isolates). Interestingly, the majority (31 of 35; 89%) of E. coli O157:H7 isolates characterized in this study belonged mainly to the phage types previously found in STEC O157:H7 strains associated with severe human disease in Europe and Canada. Pulsed-field gel electrophoresis (PFGE) of 32 isolates revealed 14 XbaI-PFGE groups (I to XIV) of similarity >85%, with 23 (72%) isolates grouped in five clusters. Some isolates from different districts presented a high clonal relatedness. Thus, PFGE group VIII clustered eleven strains from nine different districts. The broad range of PFGE subtypes found in this study demonstrates the natural occurrence of many genetic variants among STEC O157:H7 spread in Lima.     

Volatile compounds on the surface and within Iberian dry-cured loin

The profile of volatile compounds from external and internal areas of Iberian dry-cured loin was studied by headspace solid-phase microextraction. Higher levels of 16 volatile compounds (hexane, decane, 3-methylbutanal, several sulphur compounds and some aromatic hydrocarbons) were detected in the outer part of the loins. These differences could be owing to several factors, such as greater exposure to oxygen and dehydration conditions in the surface of the product, which favour oxidation reactions and Strecker degradation of amino acids. Moreover, the addition of spices on the surface and the proximity of a mould layer growing on the surface of the product could also contribute to the higher levels of these compounds on the external layer. However, other sulphur compounds coming from spices showed similar levels on the surface and within the loins. This different behaviour could be a consequence of different diffusion rates depending on the features of the compound and the matrix.     

Effect of slurry ice on chemical changes related to quality loss during European Hake (Merluccius merluccius) chilled storage

Slurry ice is a biphasic system consisting of small spherical ice crystals surrounded by seawater at subzero temperature. Its employment was evaluated in the present work as a new chilled storage method for whole European Hake (Merluccius merluccius) and compared to traditional flake icing. Different chemical analyses (nucleotide degradation, formaldehyde formation, lipid hydrolysis and oxidation, interaction compound formation, and electrophoretic protein profiles) related to quality changes were analysed and compared to sensory evaluation. An inhibitory effect on quality loss mechanisms was observed for the slurry ice treatment, according to nucleotide degradation (K value), free formaldehyde content, browning development, and sarcoplasmic protein profiles. No differences in lipid hydrolysis and oxidation could be distinguished by a comparison between both icing conditions. The sensory analysis showed a higher shelf-life time for slurry icing than flake icing (12 days and 5 days, respectively). Results confirm the practical advantages of using slurry ice as a chilled storage method.     

Characteristics of lactose-free frozen yogurt with κ-carrageenan and corn starch as stabilizers

Frozen yogurt is a type of dairy product that is considered to be a more healthful alternative to conventional ice cream due to its lower fat content and the presence of viable lactic acid bacteria. Lactose-free products are a growing trend in the dairy industry, and lactose-free yogurts and ice creams can both be found on the market. However, lactose-free frozen yogurt has not yet reached the market. In this study, we aimed to investigate the effect of adding κ-carrageenan (0.05, 0.1, and 0.15%) and corn starch (1, 2, and 3%) on acidity, texture, viscosity, overrun, melting properties, color attributes, and sensory characteristics of lactose-free frozen yogurts. Lactose was reduced by enzymatic hydrolysis during the fermentation process. The effectiveness of the hydrolysis was measured by HPLC, and lactose was reduced to 0.05% after 80 min of incubation with the enzyme. The addition of stabilizers did not change overrun and melting properties of frozen yogurt, but it did affect pH, titratable acidity, and color parameters. The product with 0.15% κ-carrageenan had the highest hardness and stickiness values. Moreover, κ-carrageenan had a positive effect on sensory attractiveness of lactose-free frozen yogurt, and it reduced the coarse texture in comparison with the control without stabilizers. A lactose-free frozen yogurt with good quality and nutritional characteristics was produced, particularly with the use of κ-carrageenan as stabilizer.     

Yoghurt‐type beverage with partial substitution of milk by a chickpea extract: Effect on physicochemical and flow properties

The objective of this study was to determine the evolution of physicochemical and flow properties of a yoghurt‐type beverage partially replaced with a chickpea extract over a period of 22 days. From two chickpea extracts, Blanco Noroeste was selected for its higher protein content. Six yoghurt‐type formulations were prepared, stored at 4 °C and analysed on days 1, 8, 15 and 22. pH was 4.24–4.75, while brightness was 81.7–94.5. Flow properties of the yoghurt‐type exhibited a non‐Newtonian behaviour. From three formulations that underwent sensory evaluation, the 30:70 mix obtained the highest acceptation. This yoghurt‐type beverage exhibited characteristics similar to natural yoghurt.     

Food protozoa safety assessment and risk in school restaurants in Armenia,Colombia

This work assessed the risk of protozoa in 10 school restaurants in Armenia (Quindío, Colombia) by analyzing the presence of Cryptosporidium spp, Giardia duodenalis, Blastocystis, and Cyclospora cayetanensis DNA in the food, water, and living and inert surfaces of school restaurants and in stools of children who ate at these restaurants. Of the 213 food, water, and surface samples, 6.6% were positive using PCR to test DNA for Blastocystis; 3.8% for Cryptosporidium spp; 0.9% for G. duodenalis; and 0% for C. cayetanensis. In 187 stool samples analyzed via microscopy from children who attended the restaurants, 40 (21.4%) were positive for Blastocystis and 21 (11.2%) were positive for Giardia spp. Via PCR, 20 (10.7%) were positive for Cryptosporidium and 0 (0%) for C. cayetanensis. A higher positivity in children's stools for Blastocystis spp was correlated with lower compliance in property conditions and for higher positivity of Giardia spp in children's stool was related to lower knowledge by food manipulators. Inspection scores can identify restaurants with higher risk for protozoa infection.     

Simulation and analysis of a sugarcane juice evaporation system

The production of sugar and alcohol is the main objective of the sugarcane processing industry. The evaporation of sugarcane juice has a high energetic cost and is usually performed in multiple-effect evaporators. The loss of performance during operation due to fouling makes the process more complex. In this study, modeling, simulation, validation, and analysis were performed for a sugarcane juice industrial evaporation system (IES) composed of a falling film evaporator followed by three short vertical-tube evaporators arranged in parallel. The IES model was developed using a commercial process simulator and validated with data from the plant. The IES had marked performance losses in the first 14 days of operation, mainly due to fouling in the first effect, with a 30% decrease in the evaporation rate.