Journal Articles
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Item Emulsification Properties of Garlic Aqueous Extract: Effect of Heat Treatment and pH Modification(MDPI, Basel, Switzerland, 2023-10-10) Bravo-Núñez Á; Golding M; Gómez M; Matia-Merino L; Dai HDespite the broad research available in the literature dealing with garlic health benefits, little information is found regarding the functional properties of garlic components. The aim of this study was to evaluate the emulsification properties of garlic water-soluble compounds (GWSC), encompassing proteins, saponins, and carbohydrates, after heat treatment (10 min at 95 °C) or pH adjustments (2.5, 3.5, and 7.8). After the various treatments, the extracts were used as such or filtrated (0.45 µm), and 10% soybean oil-in-water emulsions were prepared using low (0.48%) or high (6.55% wt/wt) extract concentrations. Results showed that whereas at low GWSC concentrations, both heating and acidifying resulted in the formation of bigger oil droplet sizes (i.e., from d32 = 0.36 µm using unmodified extract to d32 = 7-22 µm at pH 2.5 with or without extract filtration), the effects were opposite at the highest GWSC concentration. In the latter, heat treatment clearly reduced the droplet size as observed from the micrographs as well as the degree of creaming, though the occurrence of depletion and/or bridging flocculation was still strong. The acidification of the extract at this high GWSC concentration significantly reduced the droplet size, as observed from the micrographs; however, a strong flocculation was observed. Removal of protein aggregates, and possibly also saponin micelles, from the extract resulted in an obvious increase in emulsion droplet size. This research brings valuable insights on this study and utilisation of novel natural food emulsifiers from plant sources.Item Evaluation of formulation design on the physical and structural properties of commercial cream cheeses(John Wiley and Sons Ltd on behalf of Institute of Food, Science and Technology (IFSTTF)., 2022-10) Kim J; Watkinson P; Matia-Merino L; Smith JR; Golding MThis study investigated how the compositional properties and formulation design of commercial cream cheese products model cheese influenced physical and structural properties as compared to a model cheese composition. Of the seven products evaluated, three were block format (B), two were spreadable (S) and two were spreadable light (SL), with fat contents ranging from 13.7 to 35.7%. The majority of cream cheese products indicated the inclusion of starter culture, and all formulations contained one or more stabilisers. Protein/moisture (p/m) ratio, i.e. the effective protein concentration in the non-fat substance, was seen to most strongly correlate with material properties, with a positive slope for fracture stress (R2 = 0.808) and modulus of deformability (R2 = 0.721). In terms of outliers, the datapoint for SL2 on this modulus versus p/m graph was lower than its regression line, and one rationale is that lower fat content (13.7%) gave a lower modulus from the milkfat component at 10°C test temperature. B1, with the highest p/m of 0.17, had a more dense distribution of larger fat globules coated with proteins than B2 and B3. Fracture stress and modulus of deformability were noted to be higher for full-fat than for lower fat cheese. In all products, elastic characteristics dominated viscous flow as expected. Findings have demonstrated that significant variance exists across the material properties of commerical cream cheeses, and which shows specific dependencies on their formulation.Item 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 MWe 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.Item Soy Protein Pressed Gels: Gelation Mechanism Affects the In Vitro Proteolysis and Bioaccessibility of Added Phenolic Acids(MDPI (Basel, Switzerland), 13/01/2021) Marinea M; Ellis A; Golding M; Loveday SMIn this study, a model system of firm tofu (pressed gel) was prepared to study how the coagulation mechanism-acidification with glucono δ-lactone (GDL) or coagulation with magnesium sulphate (MgSO4)-affected the physical properties of the gels along with their in vitro proteolysis (or extent of proteolysis). The two types of gels were also fortified with 3.5 mM protocatechuic (PCA) and coumaric acid (CMA) to test whether they can be used as bioactive delivery systems. Texture analysis showed that all MgSO4-induced gels (fortified and control) had a higher hydration capacity and a weaker texture than the GDL-induced gels (p < 0.05). MgSO4 gels had almost double proteolysis percentages throughout the in vitro digestion and showed a significantly higher amino acid bioaccessibility than the GDL gels (essential amino acid bioaccessibility of 56% versus 31%; p < 0.05). Lastly, both gel matrices showed a similar phenolic acid release profile, on a percentage basis (~80% for PCA and ~100% for CMA). However, GDL gels delivered significantly higher masses of bioactives under simulated intestinal conditions because they could retain more of the bioactives in the gel after pressing. It was concluded that the coagulation mechanism affects both the macro- and microstructure of the soy protein pressed gels and as a result their protein digestibility. Both pressed gel matrices are promising delivery systems for bioactive phenolic acids.Item A standardised static in vitro digestion method suitable for food - an international consensus(Royal Society of Chemistry, 7/04/2014) Minekus M; Alminger M; Alvito P; Ballance S; Bohn T; Bourlieu C; Carriere F; Boutrou R; Corredig M; Dupont D; Dufour C; Egger L; Golding M; Karakaya S; Kirkhus B; Le Feunteun S; Lesmes U; Macierzanka A; Mackie A; Marze S; McClements DJ; Menard O; Recio I; Santos CN; Singh RP; Vegarud GE; Wickham MSJ; Weitschies W; Brodkorb ASimulated gastro-intestinal digestion is widely employed in many fields of food and nutritional sciences, as conducting human trials are often costly, resource intensive, and ethically disputable. As a consequence, in vitro alternatives that determine endpoints such as the bioaccessibility of nutrients and non-nutrients or the digestibility of macronutrients (e.g. lipids, proteins and carbohydrates) are used for screening and building new hypotheses. Various digestion models have been proposed, often impeding the possibility to compare results across research teams. For example, a large variety of enzymes from different sources such as of porcine, rabbit or human origin have been used, differing in their activity and characterization. Differences in pH, mineral type, ionic strength and digestion time, which alter enzyme activity and other phenomena, may also considerably alter results. Other parameters such as the presence of phospholipids, individual enzymes such as gastric lipase and digestive emulsifiers vs. their mixtures (e.g. pancreatin and bile salts), and the ratio of food bolus to digestive fluids, have also been discussed at length. In the present consensus paper, within the COST Infogest network, we propose a general standardised and practical static digestion method based on physiologically relevant conditions that can be applied for various endpoints, which may be amended to accommodate further specific requirements. A frameset of parameters including the oral, gastric and small intestinal digestion are outlined and their relevance discussed in relation to available in vivo data and enzymes. This consensus paper will give a detailed protocol and a line-by-line, guidance, recommendations and justifications but also limitation of the proposed model. This harmonised static, in vitro digestion method for food should aid the production of more comparable data in the future.