Tailoring yield stress and viscosity of concentrated microgel suspensions by means of adding immiscible liquids

Inline Particle Size Analysis during Technical-Scale Processing of a Fermented Concentrated Milk Protein-Based Microgel Dispersion: Feasibility as a Process Control

Particle size is not only important for the sensory perception of fat-free fermented concentrated milk products, but also for processing operations because of the direct relationship with apparent viscosity. The aim of this study was to apply inline particle size analysis using focused beam reflectance measurement (FBRM) to obtain real-time information regarding the particle size of a fat-free fermented concentrated milk product, namely, fresh cheese. By comparing inline particle size data to offline particle size, apparent viscosity, protein content and processing information, the potential to use inline particle size analysis as a process monitoring and control option during fresh cheese production was assessed. Evaluation of inline particle size after fermentation and before further processing, e.g., after a buffering tank, shows promise as a means to control variance of product entering downstream processing and, thus, improve final product consistency over time. Measurement of inline particle size directly before filling could allow for precise control of final product characteristics by the use of mechanical or mixing devices placed before the inline measurement. However, attention should be given to the requirements of the inline measurement technology for accurate measurement, such as product flow rate and pressure.

Tailoring the Textural Characteristics of Fat-Free Fermented Concentrated Milk-Protein Based Microgel Dispersions by Way of Upstream, Downstream and Post-Production Thermal Inputs

There is a growing demand for new strategies to tailor the texture of fat-free fermented concentrated milk products, also referred to as milk protein-based (MPb) microgel dispersions. Methods should be easy to incorporate into the production scheme, offer labelling without added components and be cost-efficient. Thermal treatments are traditionally used upstream (milk heating) and downstream (pre-concentration heating) in the production of these dispersions, though there is little knowledge as to the effects that combinations of different thermal input levels have on final texture. Therefore, this study investigated combinations of thermal input at different intensities and steps in the production scheme at the pilot scale and the relationships with texture. We demonstrated that increasing the intensity of upstream milk heat treatment, in combination with downstream pre-concentration heating, increases gel firmness and apparent viscosity. Downstream pre-concentration heating produces final fat-free fermented concentrated MPb microgel particles that are resistant to post-heating aggregation. On the other hand, omission of downstream pre-concentration heating results in smaller particles that are sensitive to post-heating aggregation. Furthermore, gel firmness and apparent viscosity increase with post-heating. Consequently, combining different levels of thermal inputs upstream, downstream (pre-concentration) and post-production, can produce fat-free fermented concentrated MPb microgel dispersions with a range of different textures.

Fat-free fermented concentrated milk products as milk protein-based microgel dispersions: Particle characteristics as key drivers of textural properties

The popularity of fat-free fermented concentrated milk products, such as fresh cheeses and high-protein yogurt, has increased over the recent years, attributed to greater availability and improvements in taste and texture. These improvements have been achieved through modifications and new developments in processing technologies, for example, higher heat treatment intensities and incorporating different membrane filtration technologies. Though numerous processing parameters are discussed in the literature, as well as reasons behind the developments, detailed examinations of how process modifications affect the final textural attributes of these products are lacking. To draw links between processing parameters and texture, we review the literature on fat-free fermented concentrated milk products from the perspective of fermented milk protein-based microgel particles as the basic structural unit. At each main processing step, relationships between process parameters, micro- and macrostructural and sensory (textural) properties are discussed.An overview of particle characteristics that drive structural changes at each processing step is developed in relation to textural characteristics. Using this approach of assessing relationships between structural characteristics of concentrated dispersions of fat-free fermented milk protein-based microgel particles and processing parameters provides a basic context for the selection of optimal parameters to achieve a desired texture.