Over the past century, our food supply chain has developed into a global industry that continuously improves production, food properties, and food processing methods through technology.

There are many aspects of the food and beverage industry that require an understanding of surface interface interactions. In food research and development, understanding the interactions between basic biomolecules is essential. Interface rheology also plays a significant role in the stability of food.

In addition to the food itself, the appearance of food packaging must also be considered, as well as the strict cleaning requirements of food processing facilities.

[Surface Cleanliness - Cleanliness]

Do you need to characterize or evaluate surface cleanliness?

The surface surrounds us, everywhere. We live on it, utilize it, and make use of it. In many cases, surface cleanliness is of interest and importance, and in some cases even critical. The meaning of "cleanliness" is certainly a matter of definition, covering cleanliness at all scales from macro to nanoscale and beyond.

When we think of cleaning, the first type of surface that comes to our mind is the surface of the houses and objects we use in our daily lives - the kitchen, bathroom, clothes, and perhaps our transportation, such as our cars. But we also expect public places to be hygienic - restaurants, public transportation, and hospitals. The latter is one of the key areas where nanoscale cleanliness is crucial. For example, cleaning surgical tools and other surfaces in hospitals is key to successful surgery and preventing disease transmission. In industries farther away from us, such as the production and processing of food, pharmaceuticals, or other sensitive substances, shifting from manufacturing one component to another may require surface hygiene treatment between the two. Or in the electronics and optics industry, as well as in the manufacturing of circuits or coatings, the slightest dust molecule can be catastrophic. Other structures such as oil pipelines and heat exchangers in power plants may be exposed to pollution over time, accompanied by the accumulation of unwanted substances such as sediment formation, scaling, biofilm formation, and fouling, all of which may hinder their functionality.

Real time characterization and evaluation of surface cleanliness

QSense QCM-D can measure and quantify sediment, scale accumulation, and biofilm formation at the nanoscale, as well as remove the same sediment in real-time and quantitatively. Optimizing conditions to reduce or prevent the accumulation of unwanted substances is crucial, and you can characterize cleanliness before, after, and during environmental changes. In areas such as assessing kitchen cleanliness, describing biofilm formation, and measuring asphaltene adsorption in crude oil pipeline fouling, methods or additives can be developed to eliminate them.

Rapid evaluation of surface cleanliness through contact angle measurement

The efficiency of cleaning and detergent formulations can be evaluated through contact angle measurement.

The surface free energy of cleaning and treating surfaces is directly related to cleanliness and surface composition. Contact angle is one of the most sensitive surface analysis techniques, as even the nanoscale of the surface can affect wetting behavior. As a simple and fast measurement technique, contact angle is commonly used to track the efficiency of cleaning processes and cleaning solutions. Therefore, in the crucial field of cleanliness control, contact angle measurement is a very suitable quality control method. Automated Theta provides a user independent and fast method for contact angle measurement in cleanliness assessment.

The cleanliness of silicon wafers and circuit boards is an important factor in ensuring optimized functionality of the final product. The cleanliness of glass surfaces, such as inkjet printing of bottles or the use of adhesives for label applications, directly affects the quality of subsequent processing steps. Measuring glass contamination helps reduce waste and ensure efficient production.

ASTM C813-90- Hydrophobic Contamination of Glass by Contact Angle Measurement

[Surface Treatment and Coating - Paper and Packaging]

In the packaging industry, adhesion and wetting play critical roles in many processes. Packaging materials typically include various layers of different materials to meet all requirements for protecting and improving the products inside the packaging.

Optimize the adhesion of coatings on paper

Due to its relatively low cost and renewability, paper is often used as a packaging material. The barrier properties of paper are usually insufficient, so different polymer coatings are used to produce laminated materials. To ensure good mechanical properties of laminated boards, it is necessary to optimize the adhesion between polymers and paper. Wettability and surface roughness play a crucial role in adhesion and can be studied by combining contact angle and surface roughness measurements.

Before the final use of paper products, wood fibers are usually mechanically or chemically modified. The improvement of new fibers, such as utilizing nanotechnology for fiber functionalization, is also a hot topic of research. The performance of a single fiber can be studied by combining a tensiometer or optical tensiometer with a skin lift distributor.

The influence of roughness on the wettability of paper

Due to its fibrous structure, the surface of paper and cardboard is almost rough. Because it amplifies the wetting effect of surface chemicals, this roughness can affect wetting properties. In addition, different types of plasma and flame treatments used to improve printing quality can affect surface chemistry and surface roughness, so evaluating the effect of roughness on contact angle is very important.

The following example shows the effect of roughness on contact angle. Measure roughness and water contact angle at three different sample locations. Especially for hydrophilic base paper, the measured contact angle shows significant changes in the contact angle reading. After removing the influence of roughness by calculating the contact angle corrected for roughness, the contact angles become closer to each other. The difference in contact angle for roughness correction is due to the surface chemical properties of the surface. Combining contact angle and surface roughness measurement makes it possible to evaluate how roughness affects contact angle.

[Surface roughness and wettability download]

Evaluating Printing Quality through Wettability Study

Another aspect of packaging is its visual appearance. The purpose of printing on packaging is to sell internal products. The printing quality is affected by the wetting and absorbing properties of ink, as well as its spreading onto porous paper. Printing on low surface energy polymer coatings may be challenging. Optical tensiometers can be used to measure the contact angle to evaluate the influence of internal and surface sizing on the paper's absorption performance. If necessary, high-speed cameras can study very fast absorption phenomena.

Inkjet printing technology is increasingly being used for home and office printing, and has also become common in industrial printing, packaging industries, and functional printing applications. The combination of optical tensiometer and skin lift distributor can be used to demonstrate inkjet printability, especially its interaction with paper.

Study the absorption properties of coatings and ink pigments using powder wetting method with mechanical tension meter.

Evaluate the plasma treatment effect on extruded coated paper using contact angle measurement.

When printing non absorbent and low surface energy plastic surfaces, the adhesion between ink and substrate is challenging. The surface free energy of the substrate should be higher than that of the ink. To ensure good printing quality, surface treatment methods such as plasma and flame treatment should be used before printing to increase the surface free energy of the coated substrate.

Application Summary: Evaluation of Surface Treatment in the Packaging Industry

Tension measurement in inkjet printing applications

Inkjet printing is a versatile technology widely used in small home and office printing, high-speed industrial printing, and more innovative functional printing applications. Due to the crucial interaction between ink and substrate in defining inkjet printing quality, tension measurement method is widely used in this field.

The adhesion between ink and substrate can be estimated by comparing the surface tension of ink and the surface energy of substrate. Using contact angle measurement to study the absorption and spreading of droplets. The leather upgrade dispenser option of Theta optical tensiometer generates droplets of the same size as those in the real inkjet process through the use of piezoelectric driving technology.

Application Summary: Tension Measurement in Inkjet Printing

Related blog articles

The Effect of Surface Roughness on the Wettability of Paper and Paperboard

6 Reasons for Wettability Measurement in Paper and Paperboard Quality Control

Wetting Analysis of Inkjet Printing

[Interface Biology - Biomolecular Interactions]

Analysis of Interactions between Biomolecules

The analysis of interactions between biomolecules is a focus of many disciplines, from biochemistry and biotechnology to pharmaceutical science. It is the focus of basic science and applied research and development. The goal of studying the interactions between biomolecules is to go from purely acquiring knowledge and understanding biological systems and functions, to using the acquired knowledge to design drugs, biomimetic sensors, and technologies that improve our quality of life.

Basic understanding of the interactions between biomolecules

For example, in basic and applied research, a fundamental understanding of the mechanisms of lipid proteins and protein ligand interactions is a goal, in which these systems are studied and characterized to obtain the processes of biomolecule interactions.

QSense QCM-DIt is a method for real-time detection and monitoring of biological molecule interactions, such as binding and interaction dynamics, as well as structural changes in molecular layers. This method has been used to improve the understanding of target interaction mechanisms and ligand structural changes. It is also used to explore the behavior of molecules and the causes of diseases, such as protein folding disorders, peptide aggregation into long and thin fibers, amyloid like structures, etc.

Due to the fact that most biochemical reactions in nature occur on phospholipid bilayer membranes or cell membranes within cells, membranes can affect protein folding and create specific microenvironments in which reactions occur. To understand and simulate actual biological systems, it is necessary to study these interactions in an environment that simulates natural conditions. The Langmuir monolayer of membrane phospholipids has been proven to be an excellent model system for biological membranes. In drug discovery, the permeation of drugs through the cell wall and the reaction between drugs and the cell membrane are important factors in drug delivery. These can be evaluated by studying the interaction between drugs and floating biofilm models. In the food industry, the removal of allergenic proteins is very important, and a deeper understanding can be obtained through molecular level research.

Application Abstract: Interactions of biomolecules in cell membrane models.

Analysis of Biomolecular Interactions in Applied Research and Development

Once knowledge of the interaction behavior of biomolecules is established, it is possible to use this new information. In applied science, such as drug exploration, nanotoxicology, or the design of biosensors, the interactions of biomolecules are crucial, and this knowledge can be used to identify targets for new compounds and detect potential new candidate drugs.

In this context, QSense QCM-D is used to analyze proteins and their interactions with DNA, as well as to detect antibody antigen interactions. QCM-D is highly sensitive to conformational changes in the tertiary structure of small molecule bound proteins, and can be used for designing, validating, and optimizing drug compounds. For example, studying the effects of amyloid growth inhibitors, investigating the conformational effects of nucleic acid receptors, and screening compounds for their interactions with cells and protein drug targets.

The knowledge of biomolecule interactions can also be used to design biosensors and detection systems, where biological behavior is imitated and utilized, such as for detecting and diagnosing diseases.

Toxicity of nanoparticles

Nanoparticles (NPs) are now applied in many different industries, including cosmetics, paints, and coatings. Therefore, in-depth research has been conducted on the toxicity of nanoparticles. Due to its large specific surface area, inhaled nanoparticles can induce pulmonary inflammation and adverse immune reactions in the respiratory system.

Langmuir membrane analyzerThis provides a good tool for studying the effect of nanoparticles on lipid membranes. The effect of 1wt% hydroxyapatite nanoparticles on the isothermal compression curve of natural lung surfactant (Infasurf) was studied. After contact with nanoparticles, there is a significant time-dependent transition in the isothermal compression curve on the left side, indicating the inhibitory effect of surfactants.

ACS Nano 2011, 5 (8), 6410-6416. Copyright 2011 American Chemical Society. (with permission)

For more QCM-D technical information, please clickProduct page detailsFor more information on LB film technology, please click hereProduct page detailsGet to know or consult our technical engineers

[surfactant and lotion/liquid stability]

Lotion is a mixture of two or more liquids, which are usually incompatible with each other. From the thermodynamic point of view, lotion is an unstable system, because the liquid-liquid system has a natural tendency to separate and reduce its interface energy.

The stability of lotion can be defined as the ability of the system to resist the change of its physical and chemical properties with time. The stability of lotion is very important in many industrial applications, including coatings, food, agricultural formulations, personal care and petroleum. Several mechanisms such as emulsification, flocculation, and aggregation can lead to emulsion breaking.

Although the stability of lotion is necessary in most industrial products and processes, there are also some processing processes that do not require the stability of lotion. For example, crude oil recovery requires separating crude oil from water before transportation, or wastewater treatment does not require oil-water emulsions.

Prediction of emulsion stability through interface rheology testing

Interface rheology is a special branch of rheology that involves the study of specific two-dimensional systems formed at interfaces. Just as rheology studies fluid flow, interface rheology studies the flow characteristics of fluid interfaces.

Interface rheology in food and beverages

Proteins can be used as surfactants in food, but other stabilizers can also be added to improve stability. Phosphatidylcholine is one of the few natural surfactants. With the increasing attention to environmental and health issues, natural surfactants are becoming increasingly of interest to people.

Application Abstract Download: Protein Adsorption and Interfacial gel at Gas Liquid and Oil Water Interfaces

Application Digest Download: Interface Rheology of Single Molecular Layers at Gas Liquid Interfaces

Watch Webinar: Interface Rheology: From Fundamentals to Applications

Surface characterization of industrial grade non-ionic emulsifiers

Polyoxyethylene surfactants are widely used in industrial applications, such as coatings, food, agricultural formulas, personal care and petroleum, among which the stability of lotion and foam is important. Alcohol ethoxylates are replacing the more toxic alkylphenol ethoxylates traditionally used as emulsifiers in many applications. However, straight chain alcohol ethoxylates did not exhibit the same good emulsifier performance as alkylphenol ethoxylates, mainly due to the latter having a larger tail. This is due to the different sizes of polarity heads and hydrocarbon tails, which hinder the formation of tightly packed thin films at the interface.

We have studied the adsorption and surface rheological properties of two industrial grade non-ionic surfactants based on different numbers of EO groups of C10 Guerbet alcohol. They are C10EO6 and C10EO14.

The surface pressure isotherms of the two surfactants conform to the reorientation model. However, there are different interpretations of surface rheological data. It indicates that C10EO6 can be explained within the model framework of diffusion relaxation process, while C10EO14 deviates from the diffusion relaxation process and its surface rheological reaction is close to that of non-ionic polymer surfactants. Figures 1 (C10EO6) and 2 (C10EO14) show the storage modulus (E ') and loss modulus (E ") obtained by oscillating perturbations of two surfactants at two frequencies (0.02 Hz and 0.5 Hz). The solid and dashed lines are suitable experimental data obtained from the diffusion model. The results showed that only the experimental data of C10EO6 surfactant showed good consistency with the proposed model.

Figure 1. The relationship function between the storage modulus (E ', hollow symbol) and loss modulus (E ", solid symbol) of C10EO6 surfactant at two frequencies (0.02Hz triangle) and (0.5Hz diamond) and the concentration of the surfactant itself. The solid and dashed lines are the best fitting curves for the diffusion model experimental data.

Figure 2. The relationship function between the storage modulus (E ', hollow symbol) and loss modulus (E ", solid symbol) of C10EO14 surfactant at two frequencies (0.02Hz triangle) and (0.5Hz diamond) and the concentration of the surfactant itself. The solid and dashed lines are the best fitting curves for the diffusion model experimental data.

The surface rheological properties of the two surfactants indicate that they form a viscoelastic layer at the air/water interface. However, due to the different number of ethylene oxide groups, the adsorption film exhibits different behaviors. For smaller surfactants, adsorption and rheological data conform to the diffusion model, while larger C10EO14 surfactants exhibit surface behavior closer to that of polymer surfactants. Moreover, the comparison of the swelling elasticity and viscosity of the two surfactants indicates that increasing the number of EO groups can enhance elasticity. The elasticity of adsorbed surfactant film is directly related to the stability of foam and lotion. Therefore, compared to shorter C10EO6 surfactants, C10EO14 surfactants may form a more stable anti aggregation layer. However, due to the high diffusivity of surfactant in the former, C10EO6 is more capable of forming foam than C10EO14. Therefore, these results may find interesting applications to reasonably develop stable foam and lotion by using non-ionic surfactants containing oxyethylene groups.

文献依据: P. Ramírez, L.M. Pérez-Mosqueda, L.A. Trujillo-Cayado, M. Ruiz, J. Munoz, R.Miller, Equilibrium and surface rheology of two polyoxyethylene surfactants (CiEOj) differing in the number of oxyethylene groups, Colloids Surf., A 375(2011) 130–135.

Asphaltene stabilized oil water lotion

When the oil is recycled, a complex oil-water lotion is formed. Asphaltenes adsorbed at the oil-water interface tend to increase the stability of these lotion. Stable oil-water lotion is usually not required because it increases pumping and transportation costs and will corrode pipes, pumps and distillation towers.

The surface activity of asphalt can be evaluated using an optical tensiometer through simple interfacial tension measurements. By combining high-pressure chambers into the system, measurements can be taken under high pressure and high temperature.

Another widely used method is to study the interfacial rheology of oil-water interfaces. The elasticity of the interface is related to the stability of oil-water emulsions. The interfacial rheology of adsorbed asphalt layer can be studied using the oscillation droplet method. Another method is to use interface shear rheology (ISR) based on a floating needle rheometer to characterize the relationship function of asphaltene bulk density.

Brewster angle microscope can visualize the morphology of asphalt at the air-water interface.

Application Abstract Download: Protein gel Adsorption at Air Water and Oil Water Interfaces

Download Application Digest: Imaging of Thin Film Structures: Brewster Angle Microscope

Watch Webinar: Interface Rheology: From Fundamentals to Applications