Effects of high-pressure processing on the safety, quality, and shelf life of ready-to-eat meats

Ready-to-eat (RTE) meats (low-fat pastrami, Strassburg beef, export sausage, and Cajun beef) were pressure treated at 600 MPa, 20 degrees C, for 180 s to evaluate the feasibility of using high-pressure processing (HPP) for the safe shelf-life extension of these products. After processing, samples were stored at 4 degrees C for 98 days during which time microbiological enumeration and enrichments were performed. Additionally, sensory analyses were undertaken to determine consumer acceptability and purchase intent over the duration of storage. Counts of aerobic and anaerobic mesophiles, lactic acid bacteria, Listeria spp., staphylococci, Brochothrix thermosphacta, coliforms, and yeasts and molds revealed that there were undetectable or low levels for all types of microorganisms throughout storage. Comparison of consumer hedonic ratings for unprocessed and processed meats revealed no difference in consumer acceptability, and no deterioration in the sensory quality was evident for any of the products tested during the study. Additionally, inoculated pack studies were conducted to determine if HPP could be used as a postlethality treatment to reduce or eliminate Listeria monocytogenes and thus assess the potential use of HPP in a hazard analysis critical control point plan for production of RTE meats. Inoculated samples (initial level of 10(4) CFU/g) were pressure treated (600 MPa, 20 degrees C, for 180 s) and stored at 4 degrees C, and survival of L. monocytogenes was monitored for 91 days. L. monocytogenes was not detected by plating methods until day 91, but selective enrichments showed sporadic recovery in three of the four products examined. The results show that HPP at 600 MPa, 20 degrees C, for 180 s can extend the refrigerated shelf life of RTE meats and reduce L. monocytogenes numbers by more than 4 log CFU/g in inoculated product.     

Salmonella carriage in an Irish pig herd: correlation between serological and bacteriological detection methods

Salmonella carriage in pigs represents a serious health problem that undoubtedly contributes to the spread of human disease. Thus, the efficient and reliable testing of farm animals for bacteria such as Salmonella is an important aspect of any efficient control strategy. Serological analysis of 15 meat juice samples detected antibodies against Salmonella in some. but not all, of the animals identified bacteriologically as harboring the pathogen, indicating a lack of correlation between the bacteriological and serological methods used for Salmonella detection. The results suggest that testing by enzyme-linked immunosorbent assay is appropriate at the herd level, with culture methods preferable for individual animal analysis. A novel culture protocol detected Salmonella in the cecal contents of 15 pigs, whereas a method based on the European Standard identified only 9 pigs as being Salmonella-positive. During the study, an unusual finding was the relatively high incidence of Salmonella London carriage in the pigs tested.     

Microbiological risk assessment for personal care products

Regulatory decisions regarding microbiological safety of cosmetics and personal care products are primarily hazard‐based, where the presence of a potential pathogen determines decision‐making. This contrasts with the Food industry where it is a commonplace to use a risk‐based approach for ensuring microbiological safety. A risk‐based approach allows consideration of the degree of exposure to assess unacceptable health risks. As there can be a number of advantages in using a risk‐based approach to safety, this study explores the Codex Alimentarius (Codex) four‐step Microbiological Risk Assessment (MRA) framework frequently used in the Food industry and examines how it can be applied to the safety assessment of personal care products. The hazard identification and hazard characterization steps (one and two) of the Codex MRA framework consider the main microorganisms of concern. These are addressed by reviewing the current industry guidelines for objectionable organisms and analysing reports of contaminated products notified by government agencies over a recent 5‐year period, together with examples of reported outbreaks. Data related to estimation of exposure (step three) are discussed, and examples of possible calculations and references are included. The fourth step, performed by the risk assessor (risk characterization), is specific to each assessment and brings together the information from the first three steps to assess the risk. Although there are very few documented uses of the MRA approach for personal care products, this study illustrates that it is a practicable and sound approach for producing products that are safe by design. It can be helpful in the context of designing products and processes going to market and with setting of microbiological specifications. Additionally, it can be applied reactively to facilitate decision‐making when contaminated products are released on to the marketplace. Currently, the knowledge available may only allow a qualitative or semi‐quantitative rather than fully quantitative risk assessment, but an added benefit is that the disciplined structuring of available knowledge enables clear identification of gaps to target resources and if appropriate, instigate data generation.     

Modeling the growth boundary of Staphylococcus aureus for risk assessment purposes

Knowing the precise boundary for growth of Staphylococcus aureus is critical for food safety risk assessment, especially in the formulation of safe, shelf-stable foods with intermediate relative humidity (RH) values. To date, most studies and resulting models have led to the presumption that S. aureus is osmotolerant. However, most studies and resulting models have focused on growth kinetics using NaCl as the humectant. In this study, glycerol was used to investigate the effects of a glass-forming nonionic humectant to avoid specific metabolic aspects of membrane ion transport. The experiments were designed to produce a growth boundary model as a tool for risk assessment. The statistical effects and interactions of RH (84 to 95% adjusted by glycerol), initial pH (4.5 to 7.0 adjusted by HC1), and potassium sorbate (0, 500, or 1,000 ppm) or calcium propionate (0, 500, or 1,000 ppm) on the aerobic growth of a five-strain S. aureus cocktail in brain heart infusion broth were explored. Inoculated broths were distributed into microtiter plates and incubated at 37 degrees C over appropriate saturated salt slurries to maintain RH. Growth was monitored by turbidity during a 24-week period. Toxin production was explored by enterotoxin assay. The 1,280 generated data points were analyzed by SAS LIFEREG procedures, which showed all studied parameters significantly affected the growth responses of S. aureus with interactions between RH and pH. The resulting growth/no growth boundary is presented.     

Growth of Salmonella during sprouting of alfalfa seeds associated with salmonellosis outbreaks

Growth of Salmonella was assessed during sprouting of naturally contaminated alfalfa seeds associated with two outbreaks of salmonellosis. Salmonella was determined daily in sprouts and sprout rinse water samples by a three-tube most probable number (MPN) procedure and a commercial enzyme immunoassay (EIA). Growth of Salmonella in the sprouts was reflected in the rinse water, and the MPNs of the two samples were generally in agreement within approximately 1 log. The results from EIA testing of sprouts and water samples were also in agreement. The pathogen was present in the seed at less than 1 MPN/g, and it increased in number to maximum population levels of 102 to 10(3) MPN/g in one seed lot and 10(2) to 10(4) MPN/ g in the other seed lot. Maximum populations of the pathogen were apparent by day 2 of sprouting. These results show the ability of the pathogen to grow to detectable levels during the sprouting process, and they provide support for the recommendation to test the sprout water for the presence of pathogens 48 h after starting seed sprouting. The effectiveness of a 10-min, 20,0000-microg/ml (ppm) calcium hypochlorite treatment of the outbreak-associated seeds was studied. For both seed lots, the hypochlorite treatment caused a reduction, but not elimination, of Salmonella contamination in the finished sprouts. These results confirm the need to test each production batch for the presence of pathogens, even after 20,000 microg/ml (ppm) hypochlorite treatment of seeds, so that contaminated product is not distributed.     

An optimized FAIRE procedure for low cell numbers in yeast

We report an optimized low‐input FAIRE‐seq (Formaldehyde‐Assisted Isolation of Regulatory Elements‐sequencing) procedure to assay chromatin accessibility from limited amounts of yeast cells. We demonstrate that the method performs well on as little as 4 mg of cells scraped directly from a few colonies. Sensitivity, specificity and reproducibility of the scaled‐down method are comparable with those of regular, higher input amounts, and allow the use of 100‐fold fewer cells than existing procedures. The method enables epigenetic analysis of chromatin structure without the need for cell multiplication of exponentially growing cells in liquid culture, thus opening the possibility of studying colony cell subpopulations, or those that can be isolated directly from environmental samples.     

Complexity,convexity and combinations of theories

We restrict our attention to decidable quantifier-free theories, such as the quantifier-free theory of integers under addition, the quantifier-free theory of arrays under storing and selecting, or the quantifier-free theory of list structure under cons, car and cdr. We consider combinations of such theories: theories whose sets of symbols are the union of the sets of the symbols of the individual theories and whose set of axioms is the union of the sets of axioms of the individual theories. We give a general technique for determining the complexity of decidable combinations of theories, and show, for example, that the satisfiability problem for the quantifier-free theory of integers, arrays, list structure and uninterpreted function symbols under +, ≤, store, select, cons, car and cdr is NP-complete. We next consider the complexity of the satisfiability problem for formulas already in disjunctive normal form: why some combinations of theories admit deterministic polynomial time decision procedures while for others the problem is NP-hard. Our analysis hinges on the question of whether the theories being combined are convex; that is, whether any conjunction of literals in the theory can entail a proper disjunction of equalities between variables. This leads to a discussion of the role that case analysis plays in deciding combinations of theories.     

Phase Transitions and Therrnoluminescence of a Plasma-Sprayed Zinc Silicate Phosphor

A plasma-sprayed zinc silicate phosphor was heat-treated at ∼800°C informing gas; the major phase present was the metastable β phase, as revealed by bright yellow fluorescence under uv excitation. On heat treatment at ∼1000°C in air, a green, fluorescence developed as a result of the formation of the stable a phase. However, its thermo luminescence characteristics were different from those of the original P1 phosphor used for spraying     

Comparison of the wear resistance of various grades of cemented carbides that may find application in wood machining

A laboratory test is described in which specimens of rectangular cemented carbide tool inserts of a standard size are allowed to slide against a rapidly rotating fiberboard disc in either the presence or the absence of a mist spray of a dilute organic acid (tannic acid or acetic acid) to simulate the cutting of green wood and cured wood respectively. It is shown that the worn surfaces of cemented carbide tools used in (field) service are remarkably similar to the worn surfaces of specimens used in the laboratory (simulation) tests.Extensive results are presented that show quantitatively the progressive wear of a wide range of cemented carbides as a function of time for sliding under wet and dry conditions. It is shown that wear depends on the type and amount of binder present in the cemented carbide and on the nature of the environment. Materials with Co-Cr and Ni-Cr binders containing significant amounts of chromium showed the greatest resistance to wear.     

Biomagnification of perfluoroalkyl compounds in the bottlenose dolphin (Tursiops truncatus) food web

The environmental distribution and the biomagnification of a suite of perfluoroalkyl compounds (PFCs), including perfluorooctane sulfonate (PFOS) and C8 to C14 perfluorinated carboxylates (PFCAs), was investigated in the food web of the bottlenose dolphin (Tursiops truncatus). Surficial seawater and sediment samples, as well as zooplankton, fish, and bottlenose dolphin tissue samples, were collected at two U.S. locations: Sarasota Bay, FL and Charleston Harbor, SC. Wastewater treatment plant (WWTP) effluents were also collected from the Charleston area (n = 4). A solid-phase extraction was used for seawater and effluent samples and an ion-pairing method was used for sediment and biotic samples. PFCs were detected in seawater (range <1-12 ng/L), sediment (range <0.01-0.4 ng/g wet weight (ww)), and zooplankton (range 0.06-0.3 ng/g ww). The highest PFC concentrations were detected in WWTP effluents, whole fish, and dolphin plasma and tissue samples in which PFOS, C8 and C10-PFCAs predominated in most matrices. Contamination profiles varied with location suggesting different sources of PFC emissions. Biomagnification factors (BMFs) ranged from <1 to 156 at Sarasota Bay and <1 to 30 at Charleston. Trophic magnification factors (TMFs) for PFOS and C8-C11 PFCAs indicated biomagnification in this marine food web. The results indicate that using plasma and liver PFC concentrations as surrogate to whole body burden in a top marine predator overestimates the BMFs and TMFs.