Isolation and recovery of glycomacropeptide from milk whey by means of thermal treatment

During enzymatic process of cheese manufacturing, rennin cleaves κ-casein releasing two fractions: para-κ-casein and glycomacropeptide (GMP), which remains soluble in milk whey. GMP is a peptide with structural particularities such as chain carbohydrates linked to specific threonine residues, to which a great variety of biological activities is attributed. Worldwide cheese production has increased generating high volumes of milk whey that could be efficiently used as an alternative source of high quality peptide or protein in foodstuff formulations. In order to evaluate isolation and recovery on whey GMP by means of thermal treatment (90 °C), 18 samples (2 L each) of sweet whey, resuspended commercial whey (positive control) and acid whey (negative control) were processed. Indirect presence of GMP was verified using chemical tests and PAGE-SDS 15%. At 90 °C treated sweet whey, 14, 20 and 41 kDa bands were observed. These bands may correspond to olygomers of GMP. Peptide recovery showed an average of 1.5 g/L (34.08%). The results indicate that industrial scale GMP production is feasible; however, further research must be carried out for the biological and nutritional evaluation of GMP's incorporation to foodstuff as a supplement.

Antioxidant capacity of amaranth products: effects of thermal and enzymatic treatments

The effect of different process -defatting, protein concentration, thermal treatment, hydrolysis with Alcalase and in vitro digestion- on the antioxidant capacity of amaranth seeds was studied. The antioxidant capacity of the products was determined in methanolic and aqueous extracts and varied from 1.00 to 21.22 and 4.97 to 369.18 µ mol TE/g sample for DPPH and ORAC assays, respectively. The combination of protein concentration and hydrolysis with Alcalase led to products with higher antioxidant activity. However, after in vitro digestion, protein concentrate and its hydrolysate showed similar antioxidant capacity. A high correlation was observed between the antioxidant capacity and the total phenolic content for methanolic extracts, with r² values ranging from 0.6133 to 0.9352.

Phenolic content and antioxidant capacity in organically and conventionally grown eggplant (Solanum melongena) fruits following thermal processing

AbstractThermal processing and production practices used in vegetables can cause changes in their phytochemical contents. Eggplant is characterized by its high antioxidant content. The objective of this work was to determine levels of anthocyanins, polyphenols, and flavonoids and antioxidant capacity in organically and conventionally grown eggplant prepared fresh or subjected to one of three thermal preparation methods: boiling, baking or steaming. The soluble and hydrolyzable polyphenols and flavonoids content were quantified by Folin-Ciocalteu and Aluminum chloride methods, respectively. Anthocyanins were quantified according to the pH differential method. Antioxidant capacity was determined by DPPH and ORAC methods. The results showed differences between organic and conventional eggplant for some variables although cultivation method did not have a consistent effect. Hydrolysable polyphenol content was greater, and soluble and hydrolysable antioxidant capacities were higher in organically grown eggplant, while anthocyanin content was greater in conventionally grown eggplant. Fresh eggplant produced under conventional cultivation had a much greater content of anthocyanins compared to that of other cultivation method-thermal treatment combination. In general, steamed eggplant contained higher total polyphenol and flavonoid levels as well as greater antioxidant capacity. Steamed eggplant from both conventional and organic systems also had high amounts of anthocyanins compared to other thermal treatments.

Lactose hydrolysis potential and thermal stability of commercial β-galactosidase in UHT and skimmed milk

Abstract The commercial enzyme (E.C. = 3.2.1.23) from Kluyveromyces lactis (liquid) and Aspergillus oryzae(lyophilized) was investigated for its hydrolysis potential in lactose substrate, UHT milk, and skimmed milk at different concentrations (0.7; 1.0 and 1.5%), pH values (5.0; 6.0; 6.5 and 7.0), and temperature (30; 35; 40 and 55 ºC). High hydrolysis rates were observed for the enzyme from K. lactis at pH 7.0 and 40 ºC, and from A. oryzae at pH 5.0 and 55 ºC. The enzyme from K. lactis showed significantly higher hydrolysis rates when compared to A. oryzae. The effect of temperature and β-galactosidase concentration on the lactose hydrolysis in UHT milk was higher than in skimmed milk, for all temperatures tested. With respect to the thermal stability, a decrease in hydrolysis rate was observed at pH 6.0 at 35 ºC for K. lactisenzyme, and at pH 6.0 at 55 ºC for the enzyme from A. oryzae. This study investigate the hydrolysis of β-galactosidase in UHT and skimmed milk. The knowledge about the characteristics of the β-galactosidase fromK. lactis and A. oryzae enables to use it most efficiently to control the enzyme concentration, temperature, and pH in many industrial processes and product formulations.

Inactivation of Staphylococcus aureus in raw salmon with supercritical CO2 using experimental design

Abstract Considering the microbial safety of consumption of raw foods (Asian food), this study aimed to explore the inactivation S. aureus in raw salmon by supercritical CO2 treatment (SC-CO2). For this purpose, experimental design methodology was employed as a tool to evaluate the effects of pressure (120-220 bar), the depressurization rate (10 to 100 bar.min–1) and the salmon:CO2 mass relation (1:0.2 to 1:1.0). It was observed that the pressure and the depressurization rate was statistically significant, i.e. the higher the system pressure and depressurization rate, the greater the microbial inactivation. The salmon: CO2 mass relation did not influence the S. aureus inactivation in raw salmon. There was a total reduction in S. aureus with 225 bar, a depressurizing rate of 100 bar.min–1, a salmon: CO2 mass relation of 1:0.6, for 2 hours at 33 °C.

Thermal modelling of commercial lithium-ion batteries

The accelerating adoption of electrical technologies in vehicles over the recent years has led to an increase in the research on electrochemical energy storage systems, which are among the key elements in these technologies. The application of electrochemical energy storage systems for instance in hybrid electrical vehicles (HEVs) or hybrid mobile working machines allows tolerating high power peaks, leading to an opportunity to downsize the internal combustion engine and reduce fuel consumption, and therefore, CO2 and other emissions. Further, the application of electrochemical energy storage systems provides an option of kinetic and potential energy recuperation. Presently, the lithium-ion (Li-ion) battery is considered the most suitable electrochemical energy storage type in HEVs and hybrid mobile working machines. However, the intensive operating cycle produces high heat losses in the Li-ion battery, which increase its operating temperature. The Li-ion battery operation at high temperatures accelerates the ageing of the battery, and in the worst case, may lead to a thermal runaway and fire. Therefore, an appropriate Li-ion battery cooling system should be provided for the temperature control in applications such as HEVs and mobile working machines. In this doctoral dissertation, methods are presented to set up a thermal model of a single Li-ion cell and a more complex battery module, which can be used if full information about the battery chemistry is not available. In addition, a non-destructive method is developed for the cell thermal characterization, which allows to measure the thermal parameters at different states of charge and in different points of cell surface. The proposed models and the cell thermal characterization method have been verified by experimental measurements. The minimization of high thermal non-uniformity, which was detected in the pouch cell during its operation with a high C-rate current, was analysed by applying a simplified pouch cell 3D thermal model. In the analysis, heat pipes were incorporated into the pouch cell cooling system, and an optimization algorithm was generated for the estimation of the optimalplacement of heat pipes in the pouch cell cooling system. An analysis of the application of heat pipes to the pouch cell cooling system shows that heat pipes significantly decrease the temperature non-uniformity on the cell surface, and therefore, heat pipes were recommended for the enhancement of the pouch cell cooling system.

Thermal and moisture content effects on storability and seed dormancy releasing on Brachiaria brizantha cultivars

Brachiaria species normally show a double seed dormancy mechanism, mainly on fresh-harvested seeds, leading to germination percentages lower than those of viability detected by tetrazolium test (TZ) and causing problems as to storage, trading and seed inspection activities. The adoption of the methodology to detect the constants of the viability equation (high storage temperatures and fixed moisture contents) made feasible in this research to isolate the effects of 40, 50 and 65°C on B. brizantha cultivars Marandu, Mulato 1 and Mulato 2 seed dormancy releasing, after storage with moisture contents ranging from 1.9 and 17.8%. Seed samples presented high dormancy levels, detected by TZ and it was complete and partially released by chemical scarification and accelerated ageing test, respectively. No statistical differences were observed as to the speed of germination (T50); however, differences among cultivars were detected as to number of seed per gram. Sorption and desorption isotherm curves were similar for the cultivars. Seed dormancy releasing was better achieved at 40 and 50°C with mc ranging from 7.6 to 10.8%. The temperature of 50°C appears to be adequate for seed dormancy releasing in all mc analyzed. No significant seed dormancy releasing result was observed at 65°C. The cultivar Marandu presented the highest storability throughout the experiment.

Development of laboratory exercises for basic nuclear thermal hydraulics measurements

The thesis focuses on light water reactors (pressurized water reactors, boiling water reactors) and measurement techniques for basic thermal hydraulics parameters that are used in a nuclear power plant. The goal of this work is a development of laboratory exercises for basic nuclear thermal hydraulics measurements.

Determination of the thermal parameters of high-power batteries by local heat

A new approach to the determination of the thermal parameters of high-power batteries is introduced here. Application of local heat flux measurement with a gradient heat flux sensor (GHFS) allows determination of the cell thermal parameters in di_erent surface points of the cell. The suggested methodology is not cell destructive as it does not require deep discharge of the cell or application of any charge/discharge cycles during measurements of the thermal parameters of the cell. The complete procedure is demonstrated on a high-power Li-ion pouch cell, and it is verified on a sample with well-known thermal parameters. A comparison of the experimental results with conventional thermal characterization methods shows an acceptably low error. The dependence of the cell thermal parameters on state of charge (SoC) and measurement points on the surface was studied by the proposed measurement approach.

Visualization of thermal-hydraulic nodes

The purpose of this thesis was to develop a program that can illustrate thermal-hydraulic node dimensions used in SMABRE simulations. These created node illustrations are used to verify the correctness of the designed simulation model and in addition they can be included in scientific reports. This thesis will include theory about SMABRE and relevant programs that were used to achieve the ending results. This thesis will give explanations for different modules that were created and used in the finished program, and it will present the different problems encountered and provide the solutions. The most important objective in this thesis is to display the results of generic VVER-1000 node dimensions and verify the correctness in the displayed part. The finished program was created using code language Python.