Flokkur: Greinar
Recent activity has been in the development of quality index method (QIM) schemes suited to individual fish species. Earlier schemes did not take into account the differences among species. To do that, it is necessary to develop one scheme for each species, and the aim when developing QIM for various species is, also, to have the QI increase linearly with storage period of the fish expressed in equivalent days in ice. To develop any new scheme, QIM takes into account the inherent differences among fish species. It is necessary to have some specific knowledge about the fish species, to have on hand two tested and trained sensory panels, a facility to conduct storage experiments under standardized conditions, and to be able to make a statistical validation of the developed QIM scheme.
Food engineering refers to the engineering aspects of food production and processing. Food engineering includes, but is not limited to, the application of agricultural engineering and chemical engineering principles to food materials. Genetic engineering of plants and animals is not normally the work of a food engineer.
Food engineering is a very wide field of activities. Among its domain of knowledge and action are:
Design of machinery and processes to produce foods
Design and implementation of food safety and preservation measures in the production of foods
Biotechnological processes of food production
Choice and design of food packaging materials
Quality control of food production
This new book deals with food engineering research from around the globe.
The existence of endogenous acid proteinases in Alaska pollack surimi and their effect on mechanical properties of surimi films were investigated. The optimum pH of acid proteinases involved in the degradation of myosin heavy chain (MHC) was 3.0, and the optimum temperature was 45 °C. The degradation of MHC was completely inhibited by pepstatin A together with any one of cysteine proteinase inhibitors, suggesting that acid proteinases present in surimi are mainly cathepsin D and cysteine proteinases. The concomitant decrease of surimi film strength with the extent of MHC degradation was observed, but surimi films were formed even when most of MHC was degraded. The main associative forces responsible for the surimi films prepared at pH 3.0 were ionic bonds and hydrophobic interactions.
The effect of heat treatment of film-forming solutions on the properties of edible surimi films was investigated. The film-forming solutions prepared at pH 3 from frozen Alaska pollack surimi were heated to 45, 70 or 100°C to promote unfolding of surimi protein molecules. As a result, solubility, surface hydrophobicity, and reactive SH group of surimi proteins increased. After 45°C -treatment, the mechanical properties, film solubility, and protein solubility of surimi films were not affected and myosin heavy chain (MHC) of surimi proteins was degraded by endogenous acid proteinases. Conversely, at higher heating temperatures (70°C, 100°C), degradation of MHC was effectively inhibited and mechanical properties were improved, while the film solubility and protein solubility of surimi films decreased. It is revealed that the prevention of MHC degradation by heat treatment could improve mechanical properties of surimi films. The optimum condition was found to be heating the film-forming solutions (pH 3) at 70°C for 20min.
The light microclimate of phototrophic endoliths growing within the scleractinian corals Porites cylindrica and Montipora monasteriata was described by scalar irradiance microprobe measurements within different layers of the coral skeleton. Characterisation of the pigments in individual layers was done by reflectance spectroscopy with fibre-optic radiance microprobes. The spectral measurements showed the presence of an endolithic community largely comprised of the green alga Ostreobium sp. within a 1 to 2 mm thick green band 2 to 6 mm below the coral surface. Additionally, spectral signatures of cyanobacteria and anoxygenic phototrophic bacteria were detected both in the coral tissue-containing top layer and within the skeleton matrix. The light microclimate within the coral skeleton was extremely poor in visible light but enriched in far-red wavelengths. Only a fraction of the incident photosynthetically available radiation (PAR, 400 to 700 nm) penetrated the coral tissue-containing layer, wherein 90 to 99% of the incident irradiance was attenuated due to intense scattering and absorption. Near-infrared radiation (NIR, >700 to 1000 nm) was mainly scattered in the tissue-skeleton matrix and penetrated much deeper into the skeleton. Multiple scattering and light-trapping effects caused high NIR scalar irradiance levels in the topmost layers of the coral. Our data show that the endolithic community in healthy corals is strongly light-limited with respect to PAR, but not with respect to NIR in shallow waters where water absorption of NIR is not limiting. Light limitation of PAR is mainly imposed by the tissue-containing part of the coral, and could thus be alleviated during coral bleaching, resulting in blooming of the phototrophic endoliths.
To examine whether there is a relationship between the degree of Campylobacter contamination observed in product lots of retail Icelandic broiler chicken carcasses and the incidence of human disease, 1,617 isolates from 327 individual product lots were genetically matched (using the flaA short variable region [SVR[) to 289 isolates from cases of human campylobacteriosis whose onset was within approximately 2 weeks from the date of processing. When there was genetic identity between broiler isolates and human isolates within the appropriate time frame, a retail product lot was classified as implicated in human disease. According to the results of this analysis, there were multiple clusters of human disease linked to the same process lot or lots. Implicated and nonimplicated retail product lots were compared for four lot descriptors: lot size, prevalence, mean contamination, and maximum contamination (as characterized by direct rinse plating). For retail product distributed fresh, Mann-Whitney U tests showed that implicated product lots had significantly (P = 0.0055) higher mean contamination than nonimplicated lots. The corresponding median values were 3.56 log CFU/carcass for implicated lots and 2.72 log CFU/carcass for nonimplicated lots. For frozen retail product, implicated lots were significantly (P = 0.0281) larger than nonimplicated lots. When the time frame was removed, retail product lots containing Campylobacter flaA SVR genotypes also seen in human disease had significantly higher mean and maximum contamination numbers than lots containing no genotypes seen in human disease for both fresh and frozen product. Our results suggest that cases of broiler-borne campylobacteriosis may occur in clusters and that the differences in mean contamination levels may provide a basis for regulatory action that is more specific than a presence-absence standard.
Frequency and numbers of Campylobacter spp. were assessed per freshly processed, contaminated broiler carcass. Campylobacter-positive flocks were identified by cecal sample analysis at slaughter. These flocks had been tested as Campylobacter negative at 4.1 ± 0.9 d prior to slaughter. Levels of contamination were estimated using 2 sampling approaches per carcass: (1) free weep fluids and (2) whole-carcass, 100 mL of distilled water rinses. Estimations of counts were determined by directly plating dilutions of weeps and rinses onto Campy-Cefex agar and incubating the plates at 41.5°C under microaerobic atmosphere. Confirmation was provided by latex agglutination to quantify levels per milliliter of weep and per 100 mL of rinse. Thirty-two slaughter groups (∼20 carcasses per group) were compared from 2003 to 2004. The Campylobacter-positive weep frequency was 84.8%, whereas the frequency for rinse samples was 74.4% (P < 0.001). Enumeration of Campylobacter spp. on positive samples ranged from 0.70 to 6.13 log10 cfu/mL of weep (geometric mean of 2.84) and from 2.30 to 7.72 log10 cfu/100 mL of rinse (geometric mean of 4.38). The correlations between weep and rinse were 0.814 with 0.5 mL of rinse and 0.6294 when applying 0.1 mL of rinse The quantitative regression analyses for these 2 corresponding tests were log10 rinse (for 0.5 mL of inoculum) = 1.1965 log10 weep + 0.4979, and log10 rinse (for 0.1 mL of inoculum) = 1.322 log10 weep − 0.1521. FlaA SVR sequencing of isolates indicated that the same genotypes were found in weep and rinse samples. Weep and rinse sampling led to different proportions of Campylobacter-positive carcasses detection, but we demonstrated that this difference was reduced by increasing the amount of rinse fluid used for plating.
Whole meat of Blue marlin (Makaira mazara) was used to prepare edible films. Protein solubility in film-forming solutions was high at acidic and alkaline pHs, while that at neutral pH was close to zero. Acidic and alkaline pHs improved the tensile strength while the effects of pH, on elongation at break, water vapour permeability and light transmission of the films, were not significant. From the film solubility in various protein denaturants it was revealed that the main interaction responsible for the formation of acidic and alkaline pH films was hydrophobic interaction, while that for neutral pH films was ionic bonding.