Brian Degner

Factors Influencing the Freeze‐Thaw Stability of Emulsion‐Based Foods

Many of the sauces used in frozen meals are oil-in-water emulsions that consist of fat droplets dispersed within an aqueous medium. This type of emulsion must remain physically and chemically stable throughout processing, freezing, storage, and defrosting conditions. Knowledge of the fundamental physicochemical mechanisms responsible for the stability of emulsion-based sauces is needed to design and fabricate high-quality sauces with the desired sensory attributes. This review provides an overview of the current understanding of the influence of freezing and thawing on the stability of oil-in-water emulsions. In particular, it focuses on the influence of product composition (such as emulsifiers, biopolymers, salts, and cryoprotectants), homogenization conditions, and freezing/thawing conditions on the stability of emulsions. The information contained in this review may be useful for optimizing the design of emulsion-based sauces for utilization in commercial food products.

Soft matter strategies for controlling food texture: formation of hydrogel particles by biopolymer complex coacervation

Soft matter physics principles can be used to address important problems in the food industry. Starch granules are widely used in foods to create desirable textural attributes, but high levels of digestible starch may pose a risk of diabetes. Consequently, there is a need to find healthier replacements for starch granules. The objective of this research was to create hydrogel particles from protein and dietary fiber with similar dimensions and functional attributes as starch granules. Hydrogel particles were formed by mixing gelatin (0.5 wt%) with pectin (0 to 0.2 wt%) at pH values above the isoelectric point of the gelatin (pH 9, 30 °C). When the pH was adjusted to pH 5, the biopolymer mixture spontaneously formed micron-sized particles due to electrostatic attraction of cationic gelatin with anionic pectin through complex coacervation. Differential interference contrast (DIC) microscopy showed that the hydrogel particles were translucent and spheroid, and that their dimensions were determined by pectin concentration. At 0.01 wt% pectin, hydrogel particles with similar dimensions to swollen starch granules (D3,2 ≈ 23 µm) were formed. The resulting hydrogel suspensions had similar appearances to starch pastes and could be made to have similar textural attributes (yield stress and shear viscosity) by adjusting the effective hydrogel particle concentration. These hydrogel particles may therefore be used to improve the texture of reduced-calorie foods and thereby help tackle obesity and diabetes.

Creation of reduced fat foods: Influence of calcium-induced droplet aggregation on microstructure and rheology of mixed food dispersions

The impact of calcium-induced fat droplet aggregation on the microstructure and physicochemical properties of model mixed colloidal dispersions was investigated. These systems consisted of 2 wt% whey protein-coated fat droplets and 4 wt% modified starch granules heated to induce starch swelling (pH 7). Optical and confocal microscopy showed that the fat droplets were dispersed within the interstitial region between the swollen starch granules. The structural organisation of the fat droplets within these interstitial regions could be modulated by controlling the calcium concentration: (i) at a low calcium concentration the droplets were evenly distributed; (ii) at an intermediate calcium concentration they formed a layer around the starch granules; (iii) at a high calcium concentration they formed a network of aggregated droplets. Paste-like materials were produced when the fat droplets formed a three-dimensional network in the interstitial region. The properties of fat droplet-starch granule suspensions can be modulated by altering the electrostatic interactions to alter microstructure.

Reduced calorie emulsion-based foods: Protein microparticles and dietary fiber as fat replacers

The potential of using microparticulated whey protein (MWP) in combination with either modified starch or locust bean gum (LBG) as fat mimetics to fabricate reduced calorie emulsion-based sauces and dressings was studied. The influence of food matrix composition (protein, polysaccharide, and fat content), ionic strength, and pH on the properties of thermally processed model emulsions (90°C/10min) was investigated. Increasing protein concentration (2.5-7.5%) increased the mean (d3,2) particle diameter due to the formation of large protein aggregates. All MWP-containing systems had a creamy white appearance with high lightness (L*>75). Addition of fat droplets (5%) further increased their lightness (L*>90) due to enhanced light scattering. Addition of starch, LBG, or MWP increased emulsion viscosity due to the increased effective volume fraction of the dispersed phase. Addition of calcium chloride (10mM) and pH adjustment (2-8) caused little change in the physicochemical properties of the mixed systems. Overall, the appearance and rheological properties of the mixed systems were similar to commercial sauces and dressings. This study demonstrates that reduced calorie food emulsions with appearance and consistency similar to those of full-fat versions can be formulated using protein microparticles and polysaccharides.

Reduced Fat Food Emulsions: Physicochemical, Sensory, and Biological Aspects.

Fat plays multiple important roles in imparting desirable sensory attributes to emulsion-based food products, such as sauces, dressings, soups, beverages, and desserts. However, there is concern that over consumption of fats leads to increased incidences of chronic diseases, such as obesity, coronary heart disease, and diabetes. Consequently, there is a need to develop reduced fat products with desirable sensory profiles that match those of their full-fat counterparts. The successful design of high quality reduced-fat products requires an understanding of the many roles that fat plays in determining the sensory attributes of food emulsions, and of appropriate strategies to replace some or all of these attributes. This paper reviews our current understanding of the influence of fat on the physicochemical and physiological attributes of food emulsions, and highlights some of the main approaches that can be used to create high quality emulsion-based food products with reduced fat contents.