Concentrated emulsions as novel fat replacers in reduced-fat and low-fat Cheddar cheeses. Part 1. Rheological and microstructural characterization

Acid-induced conformation regulation of peanut polysaccharide and its effect on stability and digestibility of oil-in-water emulsion

BACKGROUND

Developing the stable and healthy emulsion-based food is in accord with the needs of people for health. In the present study, acidification at pH 3.0 of peanut polysaccharide (APPSI) was employed to regulate its conformation and further improve its advantages in preparing oil-in-water emulsion.

RESULTS

The results indicated that acidification induced conversion of PPSI aggregates into linear chains. Increasing concentration promoted formation of cross-linked network structure shown in transmission electron microscopy images. Consequently, the viscosity, yield stress, storage modulus and flow activation energy significantly increased, further fabricating gel structure. Moreover, aggregation behavior suggested that more exposed proteins were involved in gel structure, thereby forming many hydrophobic cores as verified by fluorescence spectroscopy of pyrene. Afterwards, emulsion characteristics indicated that APPSI produced strong and thick steric hindrance around oil droplets and the coil-like interweaved chains locked the continuous phase, bringing strong elasticity and resistance to stress and creaming. Meanwhile, the lower fatty acid in APPSI-emulsion was released after simulated gastrointestinal digestion, mainly as a result of the high retention ratio of emulsion droplets. Furthermore, the elastic and viscous Lissajous curves suggested that the structure strength of APPSI-emulsion was similar to that of the salad dressing within the strain 53.22%.

CONCLUSION

The conformation of PPSI after acidification at pH 3.0 was suitable for preparing the stable emulsion. The obtained emulsion could resist digestion and maintain a strong structure, comprising a cholesterol-free and low-fat salad dressing substitute. © 2023 Society of Chemical Industry.

Characteristics of insoluble soybean fiber (ISF) concentrated emulsions: Effects of pretreatment on ISF and freeze-thaw stability of emulsions

The properties of emulsions could be affected by the interactions between the components and network stabilization effect, which are commonly adjusted by changes in pH, ionic strength and temperature. In this work, insoluble soybean fiber (ISF) obtained via homogenization after alkaline treatment was pretreated firstly and then resultant emulsions were freeze-thawed. Heating pretreatment reduced droplet size, enhanced viscosity and viscoelasticity as well as subsequent stability of ISF concentrated emulsions, while both acidic pretreatment and salinized pretreatment decreased the viscosity and weakened the stability. Furthermore, ISF emulsions exhibited a good freeze-thaw performance which was further improved by secondary emulsification. Heating promoted the swelling of ISF and strengthened the gel-like structure of emulsions while salinization and acidization weakened the electrostatic interactions and caused the destabilization. These results indicated that pretreatment of ISF significantly influenced the concentrated emulsion properties, providing guidance for the fabrication of concentrated emulsions and related food with designed characteristics.

The colloid and interface strategies to inhibit lipid digestion for designing low-calorie food

Although fat is one of the indispensable components of food flavor, excessive fat consumption could cause obesity, metabolism syndromes and an imbalance in the intestinal flora. In the pursuit of a healthy diet, designing fat reducing foods by inhibiting lipid digestion and calorie intake is a promising strategy. Altering the gastric emptying rates of lipids as well as acting on the lipase by suppressing the enzymatic activity or limiting lipase diffusion via interfacial modulation can effectively decrease lipolysis rates. In this review, we provide a comprehensive overview of colloid-based strategies that can be employed to retard lipid hydrolysis, including pancreatic lipase inhibitors, emulsion-based interfacial modulation and fat substitutes. Plants-/microorganisms-derived lipase inhibitors bind to catalytic active sites and change the enzymatic conformation to inhibit lipase activity. Introducing oil-in-water Pickering emulsions into the food can effectively delay lipolysis via steric hindrance of interfacial particulates. Regulating stability and physical states of emulsions can also affect the rate of hydrolysis by altering the active hydrolysis surface. 3D network structure assembled by fat substitutes with high viscosity can not only slow down the peristole and obstruct the diffusion of lipase to the oil droplets but also impede the transportation of lipolysis products to epithelial cells for adsorption. Their applications in low-calorie bakery, dairy and meat products were also discussed, emphasizing fat intake reduction, structure and flavor retention and potential health benefits. However, further application of these strategies in large-scale food production still requires more optimization on cost and lipid reducing effects. This review provides a comprehensive review on colloidal approaches, design, principles and applications of fat reducing strategies to meet the growing demand for healthier diet and offer practical insights for the low-calorie food industry.

Hydration effects of insoluble soybean fiber (ISF) on rheological properties and freeze-thaw stability of ISF concentrated emulsions

BACKGROUND

Concentrated emulsions have been formulated in many foods. The insoluble soybean fiber (ISF) can be utilized as a particle to stabilize concentrated emulsions. However, the approach to control the rheological properties and stability of the ISF concentrated emulsions is still worth investigating.

RESULTS

In this study, alkali-extracted ISF was hydrated by adding sodium chloride or heating and the prepared concentrated emulsions were subjected to freeze-thawing. Compared with the original hydration method, salinization reduced the absolute ζ-potential of the ISF dispersions to 6 mV, resulting in a lower absolute ζ-potential of the concentrated emulsions, which led to a decreased electrostatic repulsion and the largest droplet size, but to the lowest apparent viscosity, viscoelastic modulus, and stability. By contrast, hydration by heating promoted the interparticle interactions, and then a decreased droplet size (54.5 μm) but with a more densely distributed droplets was observed, together with enhanced viscosity and viscoelasticity properties. The fortified network structure improved the stability of the concentrated emulsions both against high-speed centrifugation and long-term storage. Additionally, secondary emulsification after freeze-thaw further improved the performance of the concentrated emulsions.

CONCLUSION

The results suggest that the formation and stability of the concentrated emulsion could be regulated by different hydration methods of particles, which could be adjusted according to the practical applications. © 2023 Society of Chemical Industry.