Chemical and Biomolecular Engineering - Research Publications
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ItemThe effect of pH on the fat and protein within cream cheese and their influence on textural and rheological properties(Elsevier BV, 2020-12-01)The effect of variation in acid gel pH during cream cheese production was investigated. The gel microstructure was denser and cheese texture firmer, as the pH decreased from pH 5.0 to pH 4.3, despite the viscoelasticity of these gels remaining similar during heating. Protein hydration and secondary structure appeared to be key factors affecting both cheese microstructure and properties. Proteins within the matrix appeared to swell at pH 5.0, leading to a larger corpuscular structure; greater β-turn structure was also observed by synchrotron-Fourier transform infrared (S-FTIR) microspectroscopy and the cheese was softer. A decrease in pH led to a denser microstructure with increased aggregated β-sheet structure and a firmer cheese. The higher whey protein loss at low pH likely contributed to increased cheese hardness. In summary, controlling the pH of acid gel is important, as this parameter affects proteins in the cheese, their secondary structure and the resulting cream cheese.
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ItemDesign and characterization of casein-whey protein suspensions via the pH-temperature-route for application in extrusion-based 3D-Printing(Elsevier BV, 2021-03)The current interest in individualized food through additive manufacturing has identified a need for more information on the formulation and printability of potential ingredients. Here, the effect of formulation parameters of casein–whey protein suspensions like the pH (4.8–5.4) as well as the casein content (8.0–12.0% (w/w)) mixed with whey protein (2.0–3.0% (w/w)) and the effect of pre-processing parameters including the denaturation of whey proteins (80 °C, 10 min; adjusted pH 6.55, 6.9 and 7.1) on the gel formation via the pH–temperature (T)-route was studied. Rheological measurements showed that the sol–gel transition temperature (G’ = 1 Pa) decreased and the aggregation rate of the casein–whey protein suspensions increased with increasing heating pH value. The aggregation rate was considered to be a key parameter predicting the printability of formulations. By exceeding a certain aggregation rate (250 Pa/10 K), casein–whey protein suspensions were found to be printable resulting in firm and stable gels.
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ItemCharacterising the influence of milk fat towards an application for extrusion-based 3D-printing of casein-whey protein suspensions via the pH-temperature-route(ELSEVIER SCI LTD, 2021-09)This study presents the design and characterisation of casein−whey protein suspensions (8.0/10.0% (w/w) casein and 2.0/2.5% (w/w) whey protein) mixed with dairy fat (1.0, 2.5 and 5.0% (w/w) total fat) processed via the pH−temperature-route in preparation for 3D-printing. Mechanical treatment was applied to significantly decrease the particle size of the milk fat globules and increase surface area, creating small fat globules (<1 μm) covered with proteins, which could act as pseudo protein particles during gelation. Different proteins covered the fat globule surface after mechanical treatment, as a result of differences in the pH adjusted just prior to heating (6.55, 6.9 or 7.1). The protein-fat suspensions appeared similar by transmission electron cryogenic microscopy and the zeta-potential of all particles was unchanged by the heating pH, with a similar charge to the solution (~−20 mV) occurring after acidification (pH 4.8/5.0) at low temperatures (2 °C). A low heating pH (6.55) resulted in increased sol−gel transition temperatures (G՛ = 1 Pa) and a decreased rate of aggregation for protein−fat suspensions. A higher heating pH (6.9 and 7.1) caused an increased rate of aggregation (aggregation rate ≥ 250 Pa/10 K), resulting in materials more promising for application in extrusion-based printing. 3D-printing of formulations into small rectangles, inclusive of a sol−gel transition in a heated nozzle, was conducted to relate the aggregation rate towards printability.
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ItemEffects of shredding on the functionality, microstructure and proteolysis of low-moisture mozzarella cheese(ELSEVIER SCI LTD, 2021-06)Low-moisture mozzarella cheese (LMMC) is commonly shredded before packaging, however, the effects of shredding are not fully understood. Industrially-produced block and shredded LMMC were studied during 8 weeks of storage at 4 °C. Cheese shredded on 15 d and at 8 weeks of age, coated with microcrystalline cellulose and stored in a modified atmosphere (70% N₂ and 30% CO₂), had an altered microstructure after 8 weeks compared with vacuum-packed block cheese. In the latter case the fat formed a more dispersed phase. Proteolysis was higher in shredded samples and a higher level of two bacterial proteases was detected. Despite these differences, the meltability and stretchability of the block and shredded LMMC were similar. The microstructure and functionality of cheese shredded at 15 d and stored for a further 6 weeks was similar to cheese shredded at 8 weeks, suggesting there is a flexible period for performing cheese shredding processes.
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ItemStructure and functionality of almond proteins as a function of pH(ELSEVIER, 2021-10)Almond proteins have potential utility in a range of food and beverages but it is not clear how pH affects protein structure and function. The behaviour of almond protein isolate was examined under conditions of neutral and acidic pH (pH 7 and 4). The isolate was highly soluble (70–80%) at either pH. An increase in acidity lead to protein unfolding, an increase in random coil structure and the appearance of lower molecular weight proteins due to acidic hydrolysis. These structural changes at pH 4 increased the capacity for foam formation and foam stability, increased viscosity and led to concentration and age dependent thickening. Gels, similar in strength but with distinct microstructures and properties were obtained following heating. At pH 7, a particulate type gel with an interconnected protein network was formed, while the gel at pH 4 had a dense continuous protein matrix. The gels differed in their susceptibility to chemical disruption, suggesting different underlying molecular interactions. The ability to alter protein structure and properties as a function of pH and heating could be used to broaden the application of almond proteins and develop a variety of food products, such as protein supplements and vegan alternatives to traditional products.
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ItemBioactives from Whey: A Sustainable Approach to Enzymatic Production of Sialyl-N-acetyllactosamine(AMER CHEMICAL SOC, 2022-05-16)The use of dairy whey to manufacture pharmaceutical products fosters sustainable environmental and economic development. This study represents a new strategy for upgrading of whey to 3′-sialyl-N-acetyllactosamine (3′-SLN) as an important structural component of glycoproteins and a receptor analog capable of forming complexes with hemagglutinins on influenza viruses. N-Acetyllactosamine (LacNAc) was enzymatically produced and purified directly from whey with no pretreatment required. An engineered and recombinantly produced sialidase with trans-sialylation ability from the non-pathogenic Trypanosoma rangeli was then used to transfer sialic acid from whey-derived, sialylated casein glycomacropeptide (CGMP) to this LacNAc. A maximum of 0.92 mM 3′-SLN was obtained at an equimolar ratio of LacNAc to bound sialic acid in CGMP; on the other hand, a molar ratio of 10 gave a fourfold greater 3′-SLN concentration. The variations in the concentration of 3′-SLN and free sialic acid during the hydrolysis reaction were modeled under different reaction conditions using machine learning and mechanistic approaches. The mechanistic analysis of the reaction indicated that the relative initial trans-sialylation rate to hydrolysis rate is directly proportional to the initial LacNAc concentration, with the ratio of trans-sialylation to hydrolysis rate constants equal to 111 M-1. The maximum 3′-SLN yield obtained was 75% based on α-2,3-sialic acid bound to CGMP. Separation of CGMP and reuse of enzyme were also investigated in an enzymatic membrane reactor.
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ItemNo Preview AvailableNutrient enrichment of dairy curd by incorporation of whole and ruptured microalgal cells (Nannochloropsis salina)(Elsevier, 2022-12-01)This work investigated incorporation of Nannochloropsis salina into renneted dairy gels and curd. Whole and ruptured microalgal cells did not impair κ-casein macropeptide cleavage by the rennet enzyme. However, insoluble components of ruptured cells impeded gelation, presumably by hindering interactions between renneted casein micelles. Confocal imaging showed that whole cells were retained and homogenously distributed within the protein network of the gels and cooked curd, whereas ruptured algae formed large aggregates that altered the protein matrix. Eicosapentaenoic acid (EPA) in the whole microalgal cells was incorporated within the curds, with considerably less EPA retained for ruptured cells. Soluble algal debris did not impair gelation, however EPA wasn't retained in the curd. The study demonstrates that nutrient enrichment of renneted dairy products is possible by incorporating whole microalgal cells to displace milk fat with protein and the beneficial long-chain omega-3 fatty acid EPA. Future research into the optimisation of product organoleptic properties is required.
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ItemDigitally enabled approaches for the scale up of mammalian cell bioreactors(Elsevier BV, 2022-09)With recent advances in digitisation and big data analytics, more pharmaceutical firms are adopting digital tools to achieve modernisation. The biological phenomena within bioreactors are a key target for such digital approaches, as these processes are often complicated and difficult to scale. Historically, rules of thumb have been used to match performance indicators across bioreactor scales. Although such methods are well-established and frequently employed by industry, no universal solution has been developed to overcome the many challenges faced in process development and scale-up. Several computer-based methodologies can potentially be applied to bioreactor scale-up, including knowledge driven and data-driven techniques. This review assesses the state of the art in digital advances in scaling bioreactors and the advantages and limitations of scaling techniques. Traditional approaches and their constraints are outlined. The application of knowledge-based techniques is then considered and compared to data-driven models. The ability to transfer processes across bioreactor scales, to compare data and predict process indicators across scales are then examined. Finally, the role of hybrid modelling and digital twins and their potential in bioprocess development are explored.
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ItemNo Preview AvailableBeta casein proteins-A comparison between caprine and bovine milk(ELSEVIER SCIENCE LONDON, 2022-03)