The combined use of progressive and block freeze concentration in lactose‐free milk: Effect of process parameters and influence on the content of carbohydrates and proteins

Abstract

This work focuses on the study of the concentration of lactose‐free milk using a combination of progressive freezing concentration (PFC) with block freezing concentration (BFC). First, we investigated the PFC of skim lactose‐free milk applying response surface methodology. To analyze the influence of three factors (stirring rate, coolant temperature, and assay time) on the response variables (concentrate yield, efficiency of the process, concentration index, and average ice growth rate), a central composite design was used previously. It was found that all factors had a significate influence on the responses. Then, once the optimized condition for this step was chosen (time of 58 min, coolant temperature of −5°C, and mechanical stirring of 1,035 rpm), the ice obtained from it was subjected to a new freeze concentration cycle using the BFC assisted by vacuum. In the concentrated fraction of this cycle, protein and carbohydrate contents were equals to 6.7 g 100 g−1 and 10.24 g 100 g−1, respectively. The results suggest that in PFC carbohydrates accumulate more in the concentrated phase, while in BFC it is the protein that has the greatest tendency to pass into the concentrated liquid. In this approach, we believe that it is possible to combine the two techniques (PFC + vacuum‐assisted BFC) to obtain concentrates, and that they can be used for the development of innovative lactose‐free dairy products. Practical Applications The use of concentration processes can facilitate the customization of milk products rich in proteins to meet specific requirements on nutritional and functional properties, for instance in bakery products, formulated food, ice‐cream, beverages, energy drinks, and others. Moreover, since most changes occur in an aqueous environment, the removal of some part of milk water results in its preservation. Within the concentration processes, the freeze concentration emerges swiftly thanks to its inherent features, involving low‐temperature processing and selective nature of the water removal step. Because of the low temperatures used in freeze concentration, this technology is gaining in popularity as an alternative technique to the standard concentration techniques currently used in dairy processing. It offers the most enhanced functional and sensorial qualities of concentrated milk because it decreases the quality deviation by minimizing the heat abuse on sensitive milk components, such as proteins, water‐soluble vitamins, and aromatics.

Freeze concentration techniques as alternative methods to thermal processing in dairy manufacturing: A review

“…Mechanical stirring induces convection and increases the solute's mass transfer from the ice fraction to the concentrated fraction. Such a vertical system has also proven to be an efficient method for concentrating lactose-free skimmed milk (Dantas et al, 2021). The process presented an 80.81% yield rate and 62.22% efficiency rate at −5 • C, 58 min, and 1035 rpm, as well as 11.68% solids content.…”

“…Unlike SFC, the progressive freeze concentration (PFC) is based on layer crystallization, where a large mass layered ice or a single large ice crystal is formed, facilitating separation due to the crystal's adhesion to the cold surface. Aside from film freeze concentration, this method has become one of the most important ways of concentrating liquid foods, preserving its thermolabile compounds (Dantas et al, 2021;de Liz et al, 2020;Miyawaki et al, 2016;Muñoz et al, 2019;Ojeda et al, 2017; Samsuri Sánchez et al, 2010). The process consists in partially freezing the solution under constant agitation, usually employed to decrease solute's on the ice layer.…”

“…The process consists in partially freezing the solution under constant agitation, usually employed to decrease solute's on the ice layer. Generally, the ice layer is formed in tank walls (cold surface) and is easily separated from the final concentration (Figure 2) (Dantas et al, 2021;Ojeda et al, 2017). This separation can be performed by the same equipment, reducing operational costs, as well as machinery and maintenance expenses (Dadrasnia et al, 2021).…”

“…Low-weighted carbohydrates showed greater separation and concentration tendencies when compared to proteins, due to their higher molecular weight. Also, solute's mobility can be affected by molecular size and concentration (Dantas et al, 2021;Kawasaki et al, 2006). Still, such a system may be a great technique for future applications involving one or more concentration methods, due to its low equipment and maintenance costs, as well as a relatively fast processing time, since mechanical agitation increases the mass transfer phenomenon and reduces pressure, enhancing the separation process.…”

“…In minor production, several studies have shown interesting results obtained from progressive and BFC applications on various products, such as lactose-free milk (Dantas et al, 2021), fermented dairy beverages (Canella et al, 2018), different types of fresh cheese (Muñoz et al, 2018), ice cream (Barros et al, 2021;, powdered dairy products (Balde & Aïder, 2017;de Liz et al, 2020), and whey protein (Vuist et al, 2021). Considering such promising results, freeze concentration techniques show great potential to be applied industrially, offer a reduction of costs, and providing high-quality products…”