Food processing by high hydrostatic pressure

The use of high hydrostatic pressures (HHP) for food processing is finding increased application within the food industry. One of the advantages of this technology is that because it does not use heat, sensory, and nutritional attributes of the product remain virtually unaffected, thus yielding products with better quality than those processed traditional methods. HHP have the ability to inactivate microorganisms as well as enzymes responsible for shortening the life of a product. In addition to lengthening the shelf-life of food products, HHP can modify functional properties of components such as proteins, which in turn can lead to the development of new products. Equipment for large-scale production of HHP processed products are commercially available nowadays. Guacamole, sliced ham, oysters, and fruit juices are some of the products currently available on the market. HHP technology is one of the most promising nonthermal processes.     

Transport of methane and noble gases during gas push-pull tests in dry porous media

A field method called the gas push-pull test (GPPT) was previously developed and tested for the in situ quantification of aerobic methane (CH4) oxidation by soil microorganisms. The GPPT consists of an injection followed by extraction of reactant and tracer gases into and out of the soil. Quantification of microbial activities from GPPTs requires insight in the transport of reactant and tracer gases under diverse field conditions. We investigated how the transport of differenttracer gases (He, Ne, and Ar) compares to that of the reactant gas CH4 during GPPTs conducted in a well-defined, dry porous media that mimicked an open system. Transport of gaseous components during GPPT is mainly driven by advection resulting from injection and extraction and diffusion driven by concentration gradients. Regardless of the advective component (selected injection/ extraction, flow rates 0.2-0.8 L min(-1)), diffusion was the dominant transport mechanism for gaseous components. This resulted in dissimilar transport of CH4 and the tracers He and Ne. Numerical simulations of GPPTs showed that similar transport of these components is only achieved at very high injection/extraction rates that, in practice, are not feasible since they would imply extremely short duration times of GPPTs to allow for consumption of a measurable amount of reactant(s) by soil microorganisms. However, Ar transport was similar to that of CH4. Hence, Ar may be a good tracer provided that it is injected at high concentrations (e.g., >25% [v/v]) to overcome its background concentration in soil air. Using moderate injection/ extraction rates (e.g., 0.6 L min(-1)) with injected volumes of 10-30 L will result in GPPT durations of 1-3 h, which would suffice to attain a measurable consumption of reactant(s) in soils having relatively high (e.g., first-order rate constants >0.3 h(-1)) microbial activities.     

Effects of salt and temperature on proteolysis during ripening of Iberian ham

Fifty-five hams from Iberian pigs were processed using two different dry-curing techniques, traditional and modern. Salt content, non-protein nitrogen and its fractions (peptide, amino acid and volatile basic nitrogen) from Biceps femoris muscles were quantified. The existence of an overlapping effect of both temperature and salt content on the general non-protein nitrogen production was observed. The most intense proteolytic breakdown took place when higher temperatures were reached during the drying stage. The difference in salt concentration seems to contribute to generating different quantities in the non-protein nitrogen fractions. The inclusion at the end of the cellar stage of a stuffing period would permit increasing the accumulation of free amino acid in high salted hams.     

Depletion study of enrofloxacin and its metabolite ciprofloxacin in edible tissues and feathers of white leghorn hens by liquid chromatography coupled with tandem mass spectrometry

To ensure delivery of safe foods to consumers, withdrawal times for drugs must be respected according to the maximum residual limits established by regulatory agencies. Because of availability and price, feather meal is currently incorporated into animal feed as a protein source for farm species. Few data are available on residual drugs in feathers from treated animals. A depletion study was performed with laying hens treated intramuscularly with 5% enrofloxacin (Enromic) at 10 mg/kg body weight over 3 days. Thirty-three birds were treated and slaughtered at different times between 6 and 216 h after treatment; and samples of muscle plus skin, liver, kidney, and feathers were collected. High-performance liquid chromatography coupled with a tandem mass spectrometry method was validated before sample analysis to determine the decision limit, detection capability, recovery, and precision. Liver was the edible tissue with the slowest drug depletion. A withdrawal time of 6 days was calculated based on European Union maximum residual limits (100 microg/kg). A withdrawal time of 9 days was calculated based on Japan maximum residual limits (10 microg/kg). Enrofloxacin plus ciprofloxacin concentrations in feathers remained high through all sampling periods. Thus, feathers from treated animals should not be fed to food-producing animals.     

Effect of illumination on the display life of fresh pork sausages packaged in modified atmosphere. Influence of the addition of rosemary, ascorbic acid and black pepper

Pork forelegs were used for manufacturing fresh sausages, treated with different natural antioxidants (rosemary, ascorbic acid and black pepper), packaged in 80% O₂ + 20% CO₂ atmosphere and displayed at 2 ± 1 °C under different lightings (darkness, standard fluorescent, low-UV colour-balanced lamp and standard fluorescent plus a UV-filter). Two packs for each treatment were opened every 4 days for subsequent analysis of colour CIE L^∗, a^∗, b^∗, TBARS, microbial psychrotrophic aerobes and sensory discolouration and off-odour. Lighting with standard fluorescent was highly deleterious for sausage display life, which fell from 12 to 8 days due mainly to early discolouration. Inserting a UV-filter extended display life to 12 days, while the use of a low-UV lamp was not effective in protecting from discolouration. Addition of rosemary plus ascorbic acid, in the absence of black pepper, retarded discolouration only in sausages illuminated with the UV-filter, reaching a display life of 16 days, equal to that of sausages maintained in the dark.     

Atmospheric DMSO degradation in the gas phase: Cl-DMSO reaction. Temperature dependence and products

The reactions of Cl atoms and ClO radicals with CH3-SOCH3 (DMSO) have been studied using the discharge flow method with direct detection of DMSO, CO, and products by mass spectrometry. The absolute rate constant at room temperature measured for reaction 1, (CH3)2SO + Cl --> products, was k(1) = (1.7 +/- 0.3) x 10(-11) cm3 molecule(-1) s(-1). For reaction 2, (CH3)2SO + ClO --> products, only an upper limit could be established, k(2) < or = 6 x 10(-14) cm3 molecule(-1) s(-1) Reaction 1 has been found to proceed through adduct formation and further decomposition involving the cleavage of the C-S bound. The pressure effect on the Cl-DMSO reaction from 0.5 to 3 Torr was negligible, and the temperature dependence in the range 273-335 K was also very slight. The results obtained are related to previous studies of sulfur compounds, and the atmospheric implications are also discussed in relation to the homogeneous sinks of DMSO. Tropospheric lifetimes of DMSO based on average Cl and ClO concentrations and the measured rate constants have been calculated showing that the contribution of reaction 1 must be of minor relevance in the marine boundary layer. Reaction 2 is so slow that it does not play any role within the atmospheric sulfur chemistry.     

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.     

Determination of flonicamid and its metabolites in bell pepper using ultra-high-performance liquid chromatography coupled to high-resolution mass spectrometry (Orbitrap)

The development and validation of a method to determine flonicamid and its metabolites as TFNA (4-trifluoromethylnicotinic acid), TFNG (N-(4-trifluoromethylnicotinoyl) glycine) and TFNA-AM (4-trifluoromethylnicotinamide) in bell pepper samples by ultra-high-performance liquid chromatography coupled to Orbitrap mass spectrometry (UHPLC-Orbitrap-MS) was performed. A fast and simple extraction procedure with acidified acetonitrile and salts (magnesium sulfate and sodium chloride) was used. The methodology was validated, checking for specificity, recovery, precision, limits of detection (LODs) and limits of quantification (LOQs). The recoveries ranged from 84% to 98%, and precisions were lower than 17%. Finally, LODs ranged from 1 µg kg^–1 (flonicamid) to 6 µg kg^–1 (TFNA-AM), while LOQs ranged from 10 µg kg^–1 (flonicamid) to 30 µg kg^–1 (TFNA-AM). Bell pepper samples were analysed and concentrations up to 98 µg kg^–1 (flonicamid) were detected, although the sum of flonicamid and metabolites did not exceed the maximum residue limit (MRL) set by the European Union.     

Timing of the inhibitory effect of fruit on return bloom of ‘Valencia’ sweet orange (Citrus sinensis (L.) Osbeck)

BACKGROUND: In Citrus the inhibitory effect of fruit on flower formation is the main cause of alternate bearing. Although there are some studies reporting the effect on flowering of the time of fruit removal in a well‐defined stage of fruit development, few have investigated the effect throughout the entire fruit growth stage from early fruitlet growth to fruit maturity. The objective of this study was to determine the phenological fruit developmental stage at which the fruit begins its inhibitory effect on flowering in sweet orange by manual removal of fruits, and the role of carbohydrates and nitrogen in the process. RESULTS: Fruit exerted its inhibitory effect from the time it was close to reaching its maximum weight, namely 90% of its final size (November) in the present experiments, to bud sprouting (April). The reduction in flowering paralleled the reduction in bud sprouting. This reduction was due to a decrease in the number of generative sprouted buds, whereas mixed‐typed shoots were largely independent of the time of fruit removal, and vegetative shoots increased in frequency. The number of leaves and/or flowers per sprouted shoot was not significantly modified by fruit load. CONCLUSION: In ‘Valencia’ sweet orange, fruit inhibits flowering from the time it completes its growth. Neither soluble sugar content nor starch accumulation in leaves due to fruit removal was related to flowering intensity, but some kind of imbalance in nitrogen metabolism was observed in trees tending to flower scarcely. Copyright © 2010 Society of Chemical Industry