Effect Of High Hydrostatic Pressure On The Structure Of Milk Protein Concentrates And Micellar Casein Concentrates

Milk proteins are used in a wide variety of food and give structure to dairy foods like cheese and yogurt. As consumers increasingly demand high protein foods with minimal processing, high pressure processing (HPP) has received attention as a nonthermal alternative to pasteurization, but this process can also be used as a tool to structurally modify proteins. This research explores structural changes to the main classes of milk, the casein micelles and serum proteins, induced by HPP. Experiments were conducted on suspensions of milk protein concentrate (MPC) and micellar casein concentrate (MCC) at 2.5 and 10% casein (w/v), treated at 150 to 450 MPa for 15 minutes at ambient temperatures. The samples were analyzed for particle size, mineral and protein distribution, and renneting kinetics using rheology and particle sizing. Scanning electron microscopy (SEM) was also used to provide direct imaging of milk protein structure before and after pressure treatment. Increasing pressures increased levels of serum calcium by up to a factor of 4 times as well as increased levels of soluble [alpha]-caseins. In 10% MCC, pressure treatment at 150 or 450 MPa significantly increased the elastic modulus of rennet gels by up to 3 times while treatment at 250 or 350 MPa only resulted in two-fold increases and no reduction in the rennet coagulation time compared to controls. In 10% MPC, treatments led to a monotonic increase in elastic modulus and aggregation rates in rennet gels. Pressurization of 10% samples also led to the formation of weak gel structures. Scanning electron micrographs showed evidence of small spherical substructures, 15-20 nm in diameter, which were tightly networked in 10% samples treated at 450 MPa. These results present some evidence for substructure in the casein micelle and suggest that micelle formation upon pressure release may involve the formation of an intermediate. Interpretations of the data in this experiment and SEM images support the iii existence of casein submicelles as the structural unit of the casein micelle. These results also suggest that casein dissociation and reformation with HPP may be a two-stage process involving the dissociation of micelles into submicelles followed by the disintegration of submicelles into individual casein proteins while reaggregation follows this process in reverse. Pressure induced dissociation of casein was found to be both concentration and pressure level dependent. This research illustrates some effects of HPP on dairy proteins which may enable new applications for these proteins in a variety of new dairy-based and protein-fortified foods. i

Modeling Dye Assisted Photocoagulation of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is major cause of blindness in Americans aged 50 years and up. In 2010, there were more than 2 million cases of AMD in the United States and the National Eye Institute projects that there will be nearly 5.5 million cases per year by 2050. The more detrimental form of AMD, the “wet” form, is caused by the development of new blood vessels within the macular region of the eye, a condition known as choroidal neovascularization (CNV). Several treatment modalities are available for AMD, however the most common is laser photocoagulation in which the abnormal blood vessels are coagulated using a high intensity laser as a heating source. While this treatment modality is effective, high temperatures within the deep eye tissue can cause unwanted collateral damage. Optimizing this thermal treatment thus amounts to minimizing the duration of treatment such that the abnormal blood vessels are destroyed but damage to other tissues is minimized. One possible extension was also explored in this study which is the injection of highly absorbent dye into the abnormal feeder vessel to improve the laser absorbance. The model used in this study employs a 3D Cartesian geometry over which Pennes bioheat equation is solved for the temperature profile over a time scale of 1 second. The thermal damage is then analyzed by observing the temperature history in abnormal and healthy tissue with the goal of achieving a cumulative effective number of minutes at 43oC greater than 80 minutes within the target tissue, the feeder vessel, while minimizing the thermal damage elsewhere. Results from the model suggest that after 1 second of laser application, temperatures in the feeder vessel rapidly rise to a maximum of 67oC and temperatures in the retinal pigment epithelium (RPE) rise to 86oC. In the hottest section of the feeder vessel, that section which is directly exposed to the center of the laser spot, the desired thermal damage is achieved within 0.55 s. The model was assessed for sensitivity to thermal properties as well as the absorbance coefficient, μa, in the feeder vessel and RPE sections. Results from this analysis suggested a change in temperature of less than 0.5% when these parameters were varied within the reasonable limits found in the literature. This suggests good applicability of the results to individual patients. The use of dye to target and improve heat transfer is a novel improvement to the existing photocoagulation process. To assess the efficacy of such a modification, the absorbance coefficient was increased from 4610 m-1 to 9000 m-1 to simulate the effect of the dye. The results show very little variation in feeder vessel temperatures suggesting that dye assisted photocoagulation is not a large improvement from the current process. The effect of blood flow velocity was also assessed in this study. As expected, it was found that increasing blood flow velocity shifted the maximum temperature in the feeder vessel along the direction of flow and resulted in slightly lower maximum feeder vessel temperatures as the blood cools the feeder vessel by convection. The results of this study suggest that shorter treatment times may be useful in reducing collateral tissue damage, however a treatment time of 1 second is justified as a margin of safety to ensure complete destruction of the desired tissue

Differences in moisture sorption characteristics and browning of lesser mealworm (Alphitobius diaperinus) ingredients

Lesser mealworm (Alphitobius diaperinus) is an insect species that can be reared on an industrial scale for human consumption. In this study, the hydration behavior of processed lesser mealworm food ingredients (whole powder, protein concentrate, textured protein) was analyzed in comparison to whey protein concentrate and tofu. Moisture adsorption isotherms were determined gravimetrically over 0.11–0.96 water activity range at 5 and 20 °C, and seven sorption models were applied to fit the experimental data. The Guggenheim-Anderson-de Boer model performed best on the isotherms of all studied samples. The determined adsorption isotherms were type III according to Brunauer classification. Mealworm protein concentrate presented the strongest hydration capacity at 20 °C, followed by whey protein concentrate and whole mealworm powder. Textured mealworm protein and tofu exhibited similar hydration behavior at 5 °C. Moreover, browning and agglomeration of mealworm protein concentrate powder were observed at water activities of 0.73 and higher, which can be explained by its composition and porous structure and were not typical for whey protein concentrate. The moisture adsorption results are important for the prediction of lesser mealworm ingredients shelf-life or prevention of undesirable quality changes during storage, but more research on microbial growth and sensory quality is needed.</p

Vendre des bières au Cambodge – jusqu’à en mourir?

En 2000, l’ONG (organisation non gouvernementale) cambodgienne SiRCHESI (Citoyen(ne)s de Siem Reap pour la santé, l’éducation et les questions sociales) s’est intéressée de près au problème du VIH/sida et a pu constater que les vendeuses de bière se trouvaient particulièrement affectées par ce virus. Ces femmes, déjà exposées, par leur métier, à la violence et aux abus sexuels, étaient contraintes d’absorber des quantités d’alcool à la fois dangereuses et nocives et, sous-payées, de prendre le risque de se vendre. On leur refusait l’accès au traitement antirétroviral hautement actif (TAHA). L’ONG, en appliquant la recherche-action, met en place les initiatives et programmes locaux dont les objectifs sont, d’une part, d’inciter les brasseurs internationaux à prendre toutes leurs responsabilités en matière de santé et de sécurité de ces travailleuses et, d’autre part, de mettre un terme à l’inégalité de genre, en particulier en ce qui concerne l’administration du TAHA