Combination of Milk and Plant Proteins to Develop Novel Food Systems: What Are the Limits?

In the context of a diet transition from animal protein to plant protein, both for sustainable and healthy scopes, innovative plant-based foods are being developing. A combination with milk proteins has been proposed as a strategy to overcome the scarce functional and sensorial properties of plant proteins. Based on this mixture were designed several colloidal systems such as suspensions, gels, emulsions, and foams which can be found in many food products. This review aims to give profound scientific insights on the challenges and opportunities of developing such binary systems which could soon open a new market category in the food industry. The recent trends in the formulation of each colloidal system, as well as their limits and advantages are here considered. Lastly, new approaches to improve the coexistence of both milk and plant proteins and how they affect the sensorial profile of food products are discussed.

High-intensity ultrasound treatment on casein: Pea mixed systems: Effect on gelling properties.

This study aimed to investigate the suitability of the application of high-intensity ultrasounds (HIUS) to improve the acid induced gelation of mixed protein systems formed by casein micelles (CMs) and pea. The protein suspensions were prepared in different protein ratios CMs: pea (100:0, 80:20, 50:50, 20:80, 0:100) at 8% (w/w) total protein concentration. In the suspensions, the ultrasound treatment produced an increase in solubility, surface hydrophobicity, and a decrease in the samples' viscosity, with more remarkable differences in protein blends in which pea protein was the major component. However, the replacement of 20% of CMs for pea proteins highly affected the gel elasticity. Hence, the creation of smaller and more hydrophobic building blocks before acidification due to the HIUS treatment increased the elasticity of the gels up to 10 times. Therefore, high-intensity ultrasounds are a suitable green technique to increase the gelling properties of CMs: pea systems.

Heat treatment of milk protein concentrates affects enzymatic coagulation properties.

Dairy ingredients with highly concentrated protein contents are high added value products with expanding market. The manufacture of such ingredients includes a succession of unit operations of which heat treatment is a key step to guarantee the microbial safety, that induces major changes in protein structures and thus ingredients functionalities. However, due to an incomplete understanding of phenomena taking place at high protein concentrations, shedding light on their mechanisms is a scientific challenge as well as an industrial need. In this study, the influence of heat treatment (74 °C/ 30 s) of highly concentrated milk protein systems (up to 20 % w/w) on protein denaturation/aggregation and enzymatic coagulation properties was studied using an original semi-industrial approach. 10 % w/w protein solutions constituted with whey protein and casein micelles at milk ratio, standardized in osmosed water or ultrafiltration permeate were used. These protein solutions were processed in different ways prior the manufacture of powders: heat treatment of the 10 % w/w protein solution before vacuum evaporation, heat treatment of the 20 % w/w protein solution after vacuum concentration, two consecutive heat treatments before and after vacuum evaporation. A fourth powder was prepared from unheated 10 % w/w protein solution. An increase in protein concentration led to a higher heat-induced protein denaturation. This phenomenon was reduced when increasing the lactose content. The effect of heat treatment on the extent of protein denaturation was not cumulative. At high protein concentration, interactions between κ-casein and whey protein were modified compared to milk, as mainly micelle-bound aggregates were formed at pH about 6.7. This phenomenon was enhanced at low ionic strength and lactose content. Our study showed that the enzymatic coagulation properties of reconstituted protein powders could be correlated with their physico-chemical compositions. An increase in protein denaturation disrupted the gel reorganization and led to the formation of weaker gels but did not interfere on the micelles aggregation phase and the early gelation. On the contrary, an increase in ionic strength and lactose content led to higher gel time.

A critical review on surface modifications mitigating dairy fouling.

Thermal treatments performed in food processing industries generate fouling. This fouling deposit impairs heat transfer mechanism by creating a thermal resistance, thus leading to regular shutdown of the processes. Therefore, periodic and harsh cleaning-in-place (CIP) procedures are implemented. This CIP involves the use of chemicals and high amounts of water, thus increasing environmental burden. It has been estimated that 80% of production costs are owed to dairy fouling deposit. Since the 1970s, different types of surface modifications have been performed either to prevent fouling deposition (anti-fouling) or to facilitate removal (fouling-release). This review points out the impacts of surface modification on type A dairy fouling and on cleaning behaviors under batch and continuous flow conditions. Both types of anti-fouling and fouling-release coatings are reported as well as the different techniques used to modify stainless steel surface. Finally, methods for testing and characterising the effectiveness of coatings in mitigating dairy fouling are discussed.

Calcium Chelation by Phosphate Ions and Its Influence on Fouling Mechanisms of Whey Protein Solutions in a Plate Heat Exchanger.

Fouling of plate heat exchangers (PHEs) is a recurring problem when pasteurizing whey protein solutions. As Ca2+ is involved in denaturation/aggregation mechanisms of whey proteins, the use of calcium chelators seems to be a way to reduce the fouling of PHEs. Unfortunately, in depth studies investigating the changes of the whey protein fouling mechanism in the presence of calcium chelators are scarce. To improve our knowledge, reconstituted whey protein isolate (WPI) solutions were prepared with increasing amounts of phosphate, expressed in phosphorus (P). The fouling experiments were performed on a pilot-scale PHE, while monitoring the evolution of the pressure drop and heat transfer coefficient. The final deposit mass distribution and structure of the fouling layers were investigated, as well as the whey protein denaturation kinetics. Results suggest the existence of two different fouling mechanisms taking place, depending on the added P concentration in WPI solutions. For added P concentrations lower or equal to 20 mg/L, a spongy fouling layer consists of unfolded protein strands bound by available Ca2+. When the added P concentration is higher than 20 mg/L, a heterogeneously distributed fouling layer formed of calcium phosphate clusters covered by proteins in an arborescence structure is observed.

Qishta-A Lebanese Heat Concentrated Dairy Product Characteristics and Production Procedures.

This study aims at exploring the chemical composition of a traditional Lebanese dairy product known as Qishta, describing the process of how to prepare it and understanding the mechanisms leading to its formation. The process of making Qishta can be divided into two phases: a hot phase during which milk is heated in a stainless-steel large shallow vessel, and a cold phase consisting of draining, cooling and packaging. According to milk temperature, two reaction zones were identified: zone A with an average temperature of 100 °C, and zone B with an average temperature of 60 °C. The results showed that Qishta had a moisture, fat, protein, lactose and ash content of 68%, 11.7%, 12.1%, 5.4% and 1.6%, respectively. Our findings showed that Qishta is a lipoprotein product having an equal amount of fat and proteins (≈12%); this composition is almost similar to that of Ricotta cheese made from whole milk. In addition, our results assert that the interactions between caseins and whey proteins lead to gel formation. Milk initial fat percentage had a significant effect on Qishta production. The highest yields were obtained when the initial fat percentage was 3.6% (182.5 g of Qishta).

Formation of ß-Lactoglobulin Aggregates from Quite, Unfolded Conformations upon Heat Activation.

In presence of calcium ions, ß-lactoglobulin (BLG) unfolds and subsequently aggregates after heating. This process has important pharmaceutical and agroalimentary applications. Nowadays, the molecular mechanism of unfolding and BLG aggregation, and the role of calcium in the mechanism, is poorly understood. Actually, in most studies, data have been acquired at room temperature, after heating and after aggregation, which makes it difficult to establish a clear causal-temporal relation between calcium binding, heat, and aggregation. Thus, the goal of the present study is to get accurate, nanoscale data about the molecular events leading to BLG unfolding and calcium-dependent aggregation. The molecular transformation of BLG during heating has been investigated, using the NMR pulse field gradient technique, operating in a high field (900 MHz). Thanks to this technique, the molecular conformation of newly formed unfolded BLG molecules can be distinguished in a large pool of native ones. The present work shows that BLG at neutral pH at 65 °C displays fast, cooperative-like unfolding, in which no long-lived intermediary state (as a molten globule one) is detected, before aggregation. These data also indicate that calcium ions bind unfolded BLG in specific sites which might be a necessary feature to form the aggregate. Finally, these data also provide an NMR-based methodology to monitor the rate of protein unfolding using NMR.

Antifouling amphiphilic silicone coatings for dairy fouling mitigation on stainless steel.

Pasteurization of dairy products is plagued by fouling, which induces significant economic, environmental and microbiological safety concerns. Herein, an amphiphilic silicone coating was evaluated for its efficacy against fouling by a model dairy fluid in a pilot pasteurizer and against foodborne bacterial adhesion. The coating was formed by modifying an RTV silicone with a PEO-silane amphiphile comprised of a PEO segment and flexible siloxane tether ([(EtO)3Si-(CH2)2-oligodimethylsiloxanem-block-(OCH2CH2)n-OCH3]). Contact angle analysis of the coating revealed that the PEO segments were able to migrate to the aqueous interface. The PEO-modified silicone coating applied to pretreated stainless steel was exceptionally resistant to fouling. After five cycles of pasteurization, these coated substrata were subjected to a standard clean-in-place process and exhibited a minor reduction in fouling resistance in subsequent tests. However, the lack of fouling prior to cleaning indicates that harsh cleaning is not necessary. PEO-modified silicone coatings also showed exceptional resistance to adhesion by foodborne pathogenic bacteria.

Storage of Micellar Casein Powders with and without Lactose: Consequences on Color, Solubility, and Chemical Modifications.

During storage, a series of changes occur for dairy powders, such as protein lactosylation and the formation of Maillard reaction products (MRPs), leading to powder browning and an increase of insoluble matter. The kinetics of protein lactosylation and MRP formation are influenced by the lactose content of the dairy powder. However, the influence of lactose in the formation of insoluble matter and its role in the underlying mechanisms is still a subject of speculation. In this study, we aim to investigate the role of lactose in the formation of insoluble matter in a more comprehensive way than the existing literature. For that, two casein powders with radically different lactose contents, standard micellar casein (MC) powder (MC1) and a lactose-free (less than 10 ppm) MC powder (MC2), were prepared and stored under controlled conditions for different periods of time. Powder browning index measurements and solubility tests on reconstituted powders were performed to study the evolution of the functional properties of MC powders during aging. Proteomic approaches [one-dimensional electrophoresis and liquid chromatography-mass spectrometry (LC-MS)] and innovative label-free quantification methods were used to track and quantify the chemical modifications occurring during the storage of the powders. Reducing the amount of lactose limited the browning of MC powders but had no effect on the loss of solubility of proteins after storage, suggesting that the action of lactose, leading to the production of MRC, does not promotes the formation of insoluble matter. Electrophoresis analysis did not reveal any links between the formation of covalent bonds between caseins and loss in solubility, regardless of the lactose content. However, LC-MS analyses have shown that different levels of chemical modifications occur during the MC powder storage, depending upon the presence of lactose. An increase of protein lactosylation and acetylation was observed for the powder with a higher lactose content, while an increase of protein deamidation and dephosphorylation was observed for that containing lower lactose. The decrease of pH in the presence of lactose as a result of Maillard reaction (MR) may explain the difference in the chemical modifications of the two powders. In view of the present results, it is clear that lactose is not a key factor promoting insolubility and for the formation of cross-links between caseins during storage. This suggests that lactosylation is not the core reaction giving rise to loss in solubility.

Investigation of secondary structure evolution of micellar casein powder upon aging by FTIR and SRCD: consequences on solubility.

BACKGROUND: Synchrotron radiation circular dichroism (SRCD) and Fourier transform infrared (FTIR) spectroscopy were used to examine the conformation evolution of micellar casein (MC) powder during storage and to determine whether the spectral changes could be related to their solubility evolution. RESULTS: A loss in intensity of SRCD spectra as a function of storage time has been observed. Quantification of secondary structures revealed losses of α-helix content during storage. Moreover, a redshift of the amide I band in the FTIR spectrum was demonstrated during the storage and was interpreted as a rearrangement of the secondary structure of the protein, which is in line with the SRCD results. The qualitative results obtained by FTIR clearly support the quantitative evolution of the secondary structure obtained by the analysis of SRCD spectra. Principal component analysis (PCA) of FTIR spectra permits a good separation of samples according to the storage time. PCA shows that the evolution of secondary structures and solubility loss are closely linked. CONCLUSION: With the quantitative data provided by SRCD spectra, it was established that, whatever the storage conditions, a unique curve exists between loss of α-helix content and loss in solubility, showing that loss of α-helix content is a marker of solubility loss for the MC powders studied. © 2017 Society of Chemical Industry.

Antifouling Biomimetic Liquid-Infused Stainless Steel: Application to Dairy Industrial Processing.

Fouling is a widespread and costly issue, faced by all food-processing industries. Particularly, in the dairy sector, where thermal treatments are mandatory to ensure product safety, heat-induced fouling represents up to 80% of the total production costs. Significant environmental impacts, due the massive consumption of water and energy, are also to deplore. Fouling control solutions are thus desperately needed, as they would lead to substantial financial gains as well as tremendous progress toward eco-responsible processes. This work aims at presenting a novel and very promising dairy fouling-mitigation strategy, inspired by nature, and to test its antifouling performances in real industrial conditions. Slippery liquid-infused surfaces were successfully designed directly on food grade stainless steel, via femtosecond laser ablation, followed by fluorosilanization and impregnation with an inert perfluorinated oil. Resulting hydrophobic surfaces (water contact angle of 112°) exhibited an extremely slippery nature (contact angle hysteresis of 0.6°). Outstanding fouling-release performances were obtained for these liquid-infused surfaces as absolutely no trace of dairy deposit was found after 90 min of pasteurization test in pilot-scale equipment followed by a short water rinse.

Damage in agitated vessels of large visco-elastic particles dispersed in a highly viscous fluid.

UNLABELLED: Many food recipes entail several homogenization steps for solid particles in hot or cold viscous liquids, such as pureed fruit and sugar, jam or sauce with mushroom pieces. Unfortunately, these unavoidable processes induce damage to the solid particles. To date, little is known of the extent and nature of the damage caused. Consequently, few clear guidelines are available for monitoring solid particle integrity when mixing solid/liquid suspensions in an agitated tank. In this study, an attempt is made to quantify the impact of various physical parameters including the influence of the rotational speed of the impeller and the processing time on particle attrition, when a suspension of large visco-elastic particles in a highly viscous fluid is mixed under isothermal condition. Pectin gel particles were immerged in a viscous liquid and homogenized for various times and rotational speeds, while the evolution of the particle's morphological parameters was monitored. Then, a set of dimensionless numbers governing the attrition mechanism is established and some empirical process relationships are proposed to correlate these numbers to the morphological characteristics and mass balance ratios. From the conditions observed, it is clear that 2 dimensionless ratios could be responsible for a change in the damaging mechanisms. These 2 ratios are the Froude and impeller rotation numbers. Finally, in the conditions tested, mass balance ratios appear to be mainly sensitive to the impeller rotational number, while the shape ratios are both impacted by the Froude and impeller rotational numbers. PRACTICAL APPLICATION: Damage to solid particles suspended in a stirred vessel reduce the final product quality in industrial cooking processes. Examples of this are fruit in jam or sauces with mushroom pieces. The attrition phenomenon was measured and the influences of the impeller rotational speed and processing time were evaluated quantitatively in function of dimensionless numbers. This study contributes key elements for the monitoring of damage to solids with a view to retaining solid integrity.