Master of Science / Food Science Institute / Jayendra K. Amamcharla / Milk protein concentrate (MPC) powders are high-protein dairy ingredients obtained from membrane filtration processes and subsequent spray drying. MPC powders have extensive applications due to their nutritional, functional, and sensory properties. However, their flow properties, rehydration behavior, and morphological characteristics are affected by various factors such as processing, storage, particle size, and composition of the powder. Literature has shown that knowledge about the powder flowability characteristics is critical in their handling, processing, and subsequent storage. For this study, FT4 powder rheometer (FT4, Freeman Technologies, UK) was used to characterize the flowability of MPC powders during storage. This study investigated the flowability and morphological characteristics of commercial MPC powders with three different protein contents (70, 80, and 90%, w/w) after storage at 25ºC and 40ºC for 12 weeks. Powder flow properties (basic flowability energy (BFE), flow rate index (FRI), permeability, etc.) and shear properties (cohesion, flow function, etc.) were evaluated. After 12 weeks of storage at 40ºC, the BFE and FRI values significantly increased (P < 0.05) as the protein content increased from 70 to 90% (w/w). Dynamic flow tests indicated that MPC powders with high protein contents displayed higher permeability. Shear tests confirmed that samples stored at 40ºC were relatively less flowable than samples stored at 25ºC. Also, the lower protein content samples showed better shear flow behavior. The results indicated that MPC powders stored at 40ºC had more cohesiveness and poor flow characteristics than MPC powders stored at 25ºC. The circle equivalent diameter, circularity, and elongation of MPC powders increased as protein content and storage temperature increased, while the convexity decreased as protein content and storage temperature increased. Overall, the MPC powders evidently showed different flow properties and morphological characteristics due to their difference in composition and storage temperature. Literature has shown various methods for determining the solubility of dairy powders, but it requires expensive instruments and skilled technicians. The front-face fluorescence spectroscopy (FFFS) coupled with chemometrics could be used as an efficient alternative, which is commonly used as fingerprints of the various food products. To evaluate FFFS as a useful tool for the non-destructive measurement of solubility in the MPC powders, commercially procured MPC powders were stored at two temperatures (25 and 40ºC) for 1, 2, 4, 8, and 12 weeks to produce powders with different rehydration properties, which subsequently influenced their fluorescence spectra. The spectra of tryptophan and Maillard products were recorded and analyzed with principal components analysis. The solubility index and the relative dissolution index (RDI) obtained from focused beam reflectance measurement was used to predict solubility and dissolution changes using fluorescence spectra of tryptophan and Maillard products. The solubility index and RDI showed that the MPC powders had decreased solubility as the storage time and temperature increased. The results suggest that FFFS has the potential to provide rapid, nondestructive, and accurate measurements of rehydration behavior in MPC powders. Overall, the results indicated that solubility and dissolution behavior of MPC powders were related to protein content and storage conditions that could be measured using FFFS.

The application of chemical additives, known as grinding aids (GA), dates back to 1930 in the cement industry. As opposed to the cement industry, where the use of GAs is on the final processing step, it could be one of the first process steps in ore beneficiation. A few investigations addressed the GA applications in ore dressing; therefore, further studies are required to better understand the GA effects on the product properties and downstream separation processes. This thesis undertakes a comparative study on the dry grinding of magnetite and the resulting product characteristics with and without GAs. The main aim is to reduce energy consumption and to address some of the challenges associated with dry processing.  The effects of GAs on the dry batch ball milling of magnetite were examined to analyze the energy consumption (Ec), particle size distribution, flow properties, bulk properties, surface morphology, particle fineness, and surface chemistry of products. Their effects on the ground product were systematically explored by sieve analysis, powder rheology, BET surface measurements, optical microscopy analysis, and zeta potential measurements. Compared with the absence of GAs, the dry grinding efficiency of magnetite increased after using GAs; however, an optimal dosage exists based on the GA type. Among GAs which considered in this investigation (Zalta™ GR20-587 (Commercial GA) and Zalta™ VM1122 (Commercial viscosity aid) as well as sodium hydroxide), Zalta™ VM1122, a polysaccharide-based additive, was the most effective GA where by using this GA; the Ec decreased by 31.1% from 18.0 to 12.4 kWh/t. The PSD became narrower and finer (P80 decreasing from 181 to 142 µm), and the proportion of the particles (38–150 µm) increased from 52.5 to 58.3%. In general, the results reveal that at sufficient GA dosages, they reduce the average particle size, increase the specific surface area, and narrow the particle size distribution. However, an excessive amount of GAs could be detrimental to the grinding performance.  Further studies on powder rheology indicated that the used GAs resulted in improved material flowability compared to grinding without additives (in the examined dosage range). The rheology measurements by the FT4 Powder Rheometer showed strong linear correlations between basic flow energy, specific energy, and the resulting work index when GAs was considered for grinding. There was a strong correlation between the grinding parameters and flow parameters (r &gt; 0.93). These results confirmed the effect of GA on ground particles' flowability. Zalta™ VM1122 showed the best performance with 38.8% reduction of basic flow energy, 20.4 % reduction of specific energy, 24.6% reduction of aerated basic flow energy, and 38.3% reduction of aerated energy. The present investigation showed that the predominant mechanism of GAs is based on the alteration of rheological properties. Further investigation on the surface properties showed that using GAs could increase the surface roughness, which is beneficial for downstream processes such as froth flotation. Zalta™ VM1122 resulted in increased surface roughness and minimum microstructural defects from the optical microscope images. Furthermore, Zalta™ VM1122 (non-ionic) resulted in similar zeta potentials and pH values for the product compared to experiments without GA. These comparable product properties are advantageous as they minimize any potential negative effects on all possible downstream processes. / Kolarctic CBC (KO1030 SEESIMA)

Additive manufacturing with the use of metals have been a steadily increasing field, being able to create products with a higher degree of complexity than traditional processing techniques. SLM is a popular AM process that uses metal powder as feedstock, and one of the key components of this process is the powder rheology. In recent years the use of a powder rheometer has been shown to be a good way of evaluating powder rheology of metal powders used within AM processes, but there is a clear lack of standardised tests and methods. In this study the Compressibility, Permeability, and Aeration test for 316L powders used within SLM processes was evaluated with a FT4 powder rheometer. 15 powders that had undergone printing in SLM processes were studied. This showed that the compressibility test had the best results in differentiating the bad preforming powders, thereafter the Aeration test. The Permeability test wasn’t able to differentiate the bad preforming powders with the settings used. This study demonstrates that some tests with a powder rheometer can evaluate the powder performance in SLM processes, but further research to evaluate the tests and standardise the settings are needed for clearer test results. / Additiv tillverkning med metall är ett område som stadigt ökat i intresse, främst på grund av möjligheten att producera produkter med en mycket högre grad av komplexitet i jämförelse med traditionella processmetoder. SLM är en populär AM process som använder metallpulver som råmaterial, och en av huvudkomponenterna för processen är pulvrets reologi. Under senare år har användningen av en pulver-reometer visat sig ett bra sätt att utvärdera pulver-reologi för metallpulver som används inom AM, men det finns en klar avsaknad av standardiserade test och metoder. I denna studie utvärderas Kompressabilitet, Permeabilitet, och Aerabilitet testen för 316L pulver producerade för SLM processer med en FT4 pulver-reometer. 15 pulver som genomgått SLM printing studerades. Studien visar att kompressabilitets testets utfall bäst överensstämde med det som setts under SLM processen, och bäst urskilde pulvren som fungerat dåligt att printa med, därefter Aerations testet. Permeabilitets testet kunde inte urskilja de sämre pulvren med de inställningarna som användes. Studien demonstrerar att vissa test och index samlade med ett pulver reometer är mer tillförlitliga än andra när det gäller för att utvärdera pulvrets prestanda inom SLM processer, men vidare forskning och studier krävs för att utvärdera testen och standardisera inställningar baserat på pulvret som testas.