Browsing by Author "Lad M"

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    Effect of Process and Formulation Variables on the Structural and Physical Properties in Cream Cheese using GDL Acidulant
    (Springer Science+Business Media, LLC, 2022-06) Kim J; Watkinson P; Lad M; Matia-Merino L; Smith JR; Golding M
    We report on the properties of analogue cream cheeses prepared using glucono delta-lactone (GDL) acidulant, notably the impact of particular processing and formulation variables, (homogenisation pressure, coagulation pH and temperature, and stabiliser level) on cream cheese physical, material and microstructural properties. Protein–protein and protein-fat interactions were seen to be the primary structural contributors to the physical properties of cream cheese. Cream cheese microstructure and its properties demonstrated well-defined correlations to specific and controllable processing elements within the manufacturing process, showing significance in interactions between parameters in multivariable linear regression analysis (P < 0.05). Summarising the effect of processing variables on key cheese properties, we observed that a progressive reduction in fat particle size of cheese milk arising from increasing homogenisation pressures was seen to increase the total surface area of fat that could be incorporated into the curd during coagulation. The greater extent of fat-fat and fat-proteins interactions during coagulation provided a reinforcing effect on the microstructure of the final cream cheese, with a corresponding increase in compressive fracture stress, shear storage modulus (G′) and shear loss modulus (G″). In terms of other processing variables, cream cheese firmness was also observed to progressively increase through lowering of coagulation pH from 5.13 to 4.33. Increasing coagulation temperature from 58 °C to 78 °C similarly caused an increase in cheese firmness. Finally, increasing the levels of added stabiliser were shown to correlate with increasing cheese firmness. Similar correlations could be observed in relation to physical properties, notably forced expressible serum separation. This model cream cheese preparation method has provided a useful model system for relating food structure to material and functional properties. In addition, it has the advantage of being able to rapidly screen many formulation and process variables because it is faster than the traditional cheesemaking. This study showed that the adjustment of process and formulation variables, either in isolation or in combination, in the manufacture of cream cheese can significantly influence the final material and textural properties of the product, thereby enabling controllable functional attributes capable of meeting different customer needs.
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    Unravelling the behaviour of curcumin nanoemulsions during in vitro digestion: Effect of the surface charge
    (Royal Society of Chemistry, 2013) Pinheiro AC; Lad M; Coimbra MA; Boland MJ; Vicente AA; Silva HD
    Oil-in-water nanoemulsions containing curcumin were prepared through high-pressure homogenization using corn oil and three different emulsifiers: Tween 20 (non-ionic), Sodium Dodecyl Sulphate (SDS, anionic) and DodecylTrimethylAmmonium Bromide (DTAB, cationic). A human gastric simulator was used as the in vitro digestion model (in which the stomach, duodenum, jejunum and ileum steps were performed) to evaluate the impact of surface charge on the digestion of the curcumin nanoemulsions. This model allowed the simulation of continuous peristaltic movements and consequently enabled a more mechanically realistic simulation of the dynamic digestion process than simple stirred vessel models. The emulsifier charge had a significant effect on the droplet size, particle electric charge and microstructure of curcumin nanoemulsions during the simulated digestion, which consequently influenced the free fatty acid release and curcumin bioavailability. The results showed the positively charged DTAB-stabilized emulsions to be the least stable during the digestion process, exhibiting the largest increase in droplet size and eventual phase separation. This also contributed to the low bioavailability of curcumin. Conversely, emulsions stabilized with Tween 20 showed retention of emulsion structure (high surface area) and greater free fatty acid production, which could explain the increased curcumin bioavailability. The emulsifier charge influenced the lipid digestion process and the bioavailability of the bioactive compound incorporated, probably by altering the ability of bile salts and digestive enzymes to adsorb onto the emulsion surfaces, thus altering the droplet size (and consequently the surface area) due to droplet breakup or coalescence within the digestive tract. The results of this work also highlighted the importance of subjecting the emulsions to a simulated gastric environment, since changes in pH, ionic strength, gastric enzyme activity and shear will impact the emulsion properties in the small-intestine. This manuscript has provided important insights into the effect of emulsifier charge on the behaviour of nanoemulsions during in vitro digestion, which is important to determine their functional performance, aiming at the optimization of nanoemulsion-based delivery systems to protect and release bioactive lipophilic compounds.