Contents

Food & Beverages Industry
The Practical Guide to Surface Science (2026)

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Written by
Dr Amit Pratap Singh
PhD, Delhi University Post Doc - AIST Japan
Guest Author
Read More
alidad
Reviewed by
Dr Alidad Amirfazli
Dr. Amirfazli, a leading expert in surface wetting and superhydrophobic coatings, has 250+ publications, edits Advances in Colloid and Interface Science, and has received multiple research awards.
Scientific Advisor & Co-founder
Read More
D54c15105cfe94f786c500e4091d6ea65457608fde49ba183c8f862814a54249?s=100&d=m
Written By

Dr Amit Pratap Singh

Guest Author

PhD, Delhi University

Post Doc - AIST Japan

alidad
Reviewed By

Dr Alidad Amirfazli

Scientific Advisor & Co-founder

Dr. Amirfazli, a leading expert in surface wetting and superhydrophobic coatings, has 250+ publications, edits Advances in Colloid and Interface Science, and has received multiple research awards.

Featured Studies & Publications

Research Paper Contact angle measurement with a smartphone
Research Paper Surface tension measurement with a smartphone using a pendant drop

This is a practical guide to Surface Science for researchers working in the Food & Beverages Industry.

In this all-new guide you’ll learn all about:

  • Crucial surface science principles
  • The significance of surface science measurements for the Food & Beverages industry
  • Applicable ASTM Standards & Guidelines

Let’s dive right in.

food and beverages scaled

Contents

measurement

Contact Angle Measurement

tension

Surface Tension Measurement

energy

Surface Energy Measurement

sliding angle

Sliding Angle Measurement

realworld

Real World Applications

standardand guide

Standards and Guidelines

Executive Summary

What it covers: How food and beverage teams use surface and interfacial tension, contact angle and surface free energy. Each measurement is tied to a real problem, such as edible coatings, emulsions, foam, cleaning checks and packaging films.
Key insights: An edible coating protects produce only when it spreads into an even film on the peel. Published packaging studies on the Dropometer show many bio based films are hydrophilic, with water contact angles that fall over the first 30 seconds.
Business value: Wetting checks screen coating formulations, emulsifiers and packaging films before long shelf life trials. One portable kit covers surface tension, contact angle and surface energy, so a food lab can compare candidates on the same measured values.
Standards to follow: ASTM D5946 and ISO 15989 describe water contact angle on corona treated polymer film, which is relevant to printed and laminated packaging. No wetting standard covers edible coatings or food emulsions, so record liquid, temperature and drop age every time.
Bottom line: Measure surface and interfacial tension while you formulate, and contact angle when a coating or package meets a surface. Start with the measurement that matches your problem, then book a 15 minute demo to try it on your own samples.

Chapter 1: Introduction

In food and beverage work, many quality problems start at an interface. A coating that beads on a waxy peel leaves gaps, and an emulsion that separates fails on the shelf. A packaging film that soaks up moisture can lose its barrier.

These are the places where wetting decides yield in food and beverage work:

The Dropometer drop shape analysis kit measures contact angle, surface and interfacial tension, surface free energy and sliding angle with one portable setup. Its method was validated against a KRUSS DSA100E in two peer reviewed papers. If you are new to the terms, start with wettability.

We use the following surface properties to understand the behavior of Food & Beverages products and improve their quality.

Chapter 2: Contact Angle Measurement

The contact angle quantifies the wettability of a surface by representing the angle between a liquid’s surface and a solid surface.
Dropletlab Research

Sample Image taken from Droplet Lab Tensiometer.

Young – Laplace Method

  • 1. This method uses the whole drop profile to calculate the contact angle value.
  • 2. This method is only compatible with an axisymmetric drop, which is not always seen in practice because a needle is typically inserted into the drop to increase or decrease the drop volume.
  • 3. This method yields more consistent results than the polynomial fitting method.

Polynomial Method

  • 1. This method uses only a portion of the drop profile to calculate the contact angle value.
  • 2. This method is compatible with both axisymmetric and non-axisymmetric drops.
  • 3. The measurement results of this method are less consistent, as they can be influenced by local surface imperfections.
Dynamic Contact Angle

Ideally, when we place a drop on a solid surface, a unique angle exists between the liquid and the solid surface. We can calculate the value of this ideal contact angle (the so-called Young’s contact angle) using Young’s equation. In practice, due to surface geometry, roughness, heterogeneity, contamination, and deformation, the contact angle value on a surface is not necessarily a single consistent value but rather falls within a range. The upper and lower limits of this range are known as the advancing and receding contact angles, respectively. The values of advancing and receding contact angles for a solid surface are highly sensitive to many parameters, such as temperature, humidity, homogeneity, and minor contamination of the surface and liquid. For example, the advancing and receding contact angles of a surface can differ at different locations.

Dynamic Contact Angle versus Static Contact Angle

Practical surfaces and coatings naturally show contact angle hysteresis, indicating a range of equilibrium values. When we measure static contact angles, we get a single value within this range. Solely relying on static measurements poses problems, like poor repeatability and incomplete surface assessment regarding adhesion, cleanliness, roughness, and homogeneity.

In practical applications, we need to understand how easily a liquid spreads (advancing angle) and how easily it is removed (receding angle), such as in painting and cleaning. Measuring advancing and receding angles offers a holistic view of liquid-solid interaction, unlike static measurements, which yield an arbitrary value within the range.

This insight is crucial for real-world surfaces with variations, roughness, and dynamics, aiding industries like cosmetics, materials science, and biotechnology in designing effective surfaces and optimizing processes.

Learn how Contact Angle measurement is done on our Tensiometer

For a more complete understanding of Contact Angle measurement, read our Contact Angle measurement: The Definitive Guide

Contact Angle measurement: The Definitive Guide

Open Benchmark Data: Contact Angle & Surface Energy

These reference measurements show how deionized water wets four standard substrates measured with the Droplet Lab Dropometer. Use them as visual and numerical benchmarks when you're checking your own sample preparation, treatments, and chemistry.

Full contact angle and surface energy datasets (including additional liquids and statistics) are available on our dataset hub.

Glass - DI Water
Glass - DI Water
Nylon - DI Water
Nylon - DI Water
PMMA - DI Water
PMMA - DI Water
Teflon - DI Water
Teflon - DI Water

The droplet images above are taken from the same benchmark series as our open dataset. For each substrate and probe liquid we report:

● Advancing and receding contact angles (and hysteresis)
● Derived surface energy (SFE) values based on multi-liquid measurements
● Measurement conditions, uncertainties, and sample preparation details

Comparing your own droplet shapes and angles against these references is a fast way to spot contamination, treatment drift, or unexpected changes in wettability.

Explore the full benchmark datasets (contact angle + surface energy)

Measurements were performed with the Droplet Lab Dropometer under controlled laboratory conditions. Treat these values as sanity checks and starting points for your own process targets, not as product specifications.

Chapter 3: Surface Tension Measurement

This property measures the force that acts on the surface of a liquid, aiming to minimize its surface area.

Surface Tension Measurement

Sample Image taken from Droplet Lab Tensiometer

Dynamic Surface Tension

Dynamic surface tension differs from static surface tension, which refers to the surface energy per unit area (or force acting per unit length along the edge of a liquid surface).

Static surface tension characterizes the equilibrium state of the liquid interface, while dynamic surface tension accounts for the kinetics of changes at the interface. These changes could involve the presence of surfactants, additives, or variations in temperature, pressure, and composition at the interface.

When to use Dynamic Surface Tension Measurement

Dynamic surface tension is essential for processes that involve rapid changes at the liquid-gas or liquid-liquid interface, such as droplet and bubble formation, coalescence (change in surface area), the behavior of foams, and the drying of paints (change in composition, e.g., evaporation of solvent). It is measured by analyzing the shape of a hanging droplet over time.

Dynamic surface tension applies to various industries, including cosmetics, coatings, pharmaceuticals, paint, food and beverage, and industrial processes, where understanding and controlling the behavior of liquid interfaces is essential for product quality and process efficiency.

Learn how Surface Tension measurement is done on our Tensiometer

For a more complete understanding of Surface Energy measurement, read our Surface Tension measurement: The Definitive Guide

Surface Tension measurement: The Definitive Guide

Chapter 4: Surface Energy Measurement

Surface energy refers to the energy required to create a unit area of a new surface.
231

Sample Image taken from Droplet Lab Tensiometer

Learn how Surface Energy measurement is done on our Tensiometer

For a more complete understanding of Surface Energy measurement, read our Surface Energy measurement: The Definitive Guide

Surface Energy measurement: The Definitive Guide

For benchmark contact angle and surface energy values on glass, nylon, PMMA, and Teflon, see the Open Benchmark Data panel above or visit our Dataset Hub for full CSV downloads.

Dataset Hub

Chapter 5: Sliding Angle Measurement

The sliding angle measures the angle at which a liquid film slides over a solid surface. It is commonly employed to assess the slip resistance of a surface.

sliding angle 1

Sample Image taken from Droplet Lab Tensiometer

Learn how Sliding Angle measurement is done on our Tensiometer

For a more complete understanding of Sliding Angle measurement, read our Sliding Angle Measurement: The Definitive Guide

Sliding Angle Measurement: The Definitive Guide

Chapter 6: Real-World Applications

Within the Food & Beverages industry, several case studies exemplify the advantages of conducting surface property measurements.

Biodegradable Films from Soyhull Cellulosic Residue with UV Protection and Antioxidant Properties Improve the Shelf-Life of Post-Harvested Raspberries

Post-harvest loss of fruits and vegetables, and health risks and environmental impact of current plastic packaging warrant new biodegradable packaging. To this end, cellulosic residue from agricultural processing byproducts is suitable due to its renewability and sustainability. Herein, soyhulls cellulosic residue was extracted, solubilized in ZnCl2 solution, and crosslinked with calcium ions and glycerol to prepare biodegradable films. The film combination was optimized using Box Behnken Design and film properties were characterized. The optimized film is translucent and exhibits tensile strength, elongation at break, water vapor permeability, hydrophobicity, and IC50 of 6.3 ± 0.6 MPa, 30.2 ± 0.9%, 0.9 ± 0.3 × 10− 10 gm− 1 s− 1 Pa− 1, 72.6◦, and 0.11 ± 0.1 g/mL, respectively. The water absorption kinetics follow the Peleg model and biodegrade within 25 days at 24% soil moisture. The film extends the shelf life of raspberries by 6 more days compared to polystyrene film. Overall, the value-added soyhull cellulosic films are advantageous in minimizing post-harvest loss and plastic-related issues, emphasizing the principles of the circular bioeconomy.

Role of the Droplet Lab Goniometer

The study used a Droplet Lab Dropometer to quantify the water contact angle (WCA) of the optimized soyhull cellulosic residue (SCR) film, as a direct readout of surface wettability / hydrophobicity:

  • Where it’s described: Methods section “2.2.6.5. Water contact angle” (page 4) specifies measuring WCA on the film using a Dropometer (Droplet Lab, Canada), capturing the droplet image via a smartphone interface, and analyzing via sessile drop software.
  • Why it mattered in this work: WCA supported how the film surface interacts with water, an important packaging-relevant property tied to moisture interactions, condensation tendency, and practical barrier behavior for fresh produce packaging.

Key quantitative outcome: The optimized film’s WCA was 72.6° (reported and visualized in Fig. 2f and discussed in the wettability section), indicating a moderately hydrophilic surface (< 90°), which aligns with the film acting as a semi-permeable packaging layer rather than a fully moisture-blocking plastic film.

Key Findings

  • Optimized formulation (SH12) (0.4 g SCR, 500 mM CaCl₂, 1.5% glycerol) achieved:
    • Tensile strength: 6.3 ± 0.6 MPa
    • Elongation at break: 30.2 ± 0.9%
    • Water vapor permeability: 0.9 ± 0.3 × 10⁻¹⁰ g·m⁻¹·s⁻¹·Pa⁻¹
  • Wettability (Droplet Lab measurement): Water contact angle = 72.6°, supporting the film’s moderately hydrophilic surface character (Fig. 2f; discussion in WCA section).
  • Functional performance: Film extended raspberry shelf-life by ~6 days at room temperature relative to polystyrene film (shelf-life study results section; Fig. 4).
  • Sustainability end-of-life: Film biodegraded within ~25 days at 24% soil moisture (biodegradation section; Fig. 2g).
  • Active packaging attributes: Film provided UV protection (transmittance results; Fig. 2c) and measurable antioxidant activity (DPPH IC50 reported in abstract and methods/results).

Why it Matters

For packaging developers and fresh-produce packers, this work demonstrates that agricultural byproduct-derived cellulose films can be engineered (via ionic crosslinking + plasticization) to hit a practical balance of mechanical integrity, breathability (moisture control), and functional protection (UV/antioxidant). The contact angle result (72.6°) provides a quick, quantitative surface check that the film is not excessively hydrophobic (which can trap moisture) nor extremely hydrophilic (which can compromise integrity), helping guide material selection, formulation optimization, and QC specifications for produce packaging where condensation management is critical.

Method Snapshot

  • Sample: Regenerated soyhull cellulosic residue film crosslinked with Ca²⁺ and plasticized with glycerol (cast from ZnCl₂-solubilized cellulose; ethanol coagulation/regeneration).
  • Droplet/angle method: Water droplet, sessile-drop contact angle measurement using Droplet Lab Dropometer with smartphone image capture and software angle calculation (static WCA implied; advancing/receding not indicated).
  • Temperature: Not explicitly stated for contact-angle testing; film drying/storage and several tests were conducted at ~22 ± 2 °C, indicating typical ambient lab conditions.
  • Surface tension: Not measured in this paper (probe liquid was water for contact-angle testing).

Data Note

  • Figure 2f (page 6) shows the water droplet image on the film and reports a water contact angle of 72.6°, which is the measurement performed using the Droplet Lab Dropometer (paired with the method description in section 2.2.6.5 on page 4).
Figure

Citation (APA Format)

Regmi, S., & Janaswamy, S. (2024). Biodegradable films from soyhull cellulosic residue with UV protection and antioxidant properties improve the shelf-life of post-harvested raspberries. Food Chemistry, 460, 140672. https://doi.org/10.1016/j.foodchem.2024.140672

View Publication →

Chocolate tempering and surface finish

Tempering controls which fat crystals form, and the result shows at the surface as gloss or bloom. Contact angle on the solid chocolate surface is one way to compare batches, because surface texture and composition both change how a drop sits. Treat it as a comparison between your own samples, not as a temper reading.

Surface roughness changes the apparent angle, so keep moulding and storage the same for every sample. Ganache and other fillings are emulsions, where emulsion stability testing by interfacial tension applies. Our contact angle measurement guide explains the method.

Chocolate tempering and surface finish

Beverage and fresh food packaging

Packaging protects a beverage or fresh product only while its surface resists moisture. Water contact angle on the packaging material, read early and again later, shows how fast water wets and soaks in. Pair it with water vapor and solubility tests, which contact angle does not replace.

Food scientists at South Dakota State University measured water contact angle on the Dropometer for wheat straw cellulose films used to pack grapes. The same research group tested soyhull films for raspberries. Both films read below 90 degrees, so the authors class them as hydrophilic.

Beverage and fresh food packaging

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Chapter 7: Standards and Guidelines

In an industry where precision reigns supreme, how can Food & Beverages manufacturers ensure their products withstand scrutiny? The answer lies in standards and guidelines: the compass that guides them through the complex maze of quality and performance.

ASTM D5946 / ISO 15989, Water Contact Angle on Corona‑Treated Polymer Films (Optional Wetting‑Tension Conversion)

What it is

A test method for measuring the water contact angle (θ) of a sessile droplet on corona‑treated polymer films to verify treatment level and assess wetting behavior. ISO 15989 uses the same water contact angle measurement and adds an optional step to determine wetting tension (γc) from a defined conversion chart (often used to bridge legacy “dyne level” specifications).

When to use it

Corona treatment verification for print/bond readiness

Use when you need an objective, auditable measure of surface wetting on PE/PP/PET (and similar) films instead of subjective dyne-solution observations.

Uniformity control across the web (edge-center-edge / lane mapping)

Use when you need to confirm treatment consistency across web width or over time (shift-start checks, electrode maintenance, storage fade studies).

In-scope / Out-of-scope

In scope
  • Water sessile-drop contact angle on corona-treated polymer film surfaces (θ as the primary measured output)
  • Multiple measurement locations to capture point-to-point variability and nonuniform treatment (mapping is expected for meaningful QC)
  • Reporting treatment level guidance using angle bands (commonly used practical ranges for many low-surface-energy films)
  • Optional ISO output: estimate wetting tension γc from θ using the ISO conversion chart (mN/m = dyne/cm)
Out of scope
  • Claiming adhesion performance from θ alone (contact angle is an indirect indicator; adhesion must be validated with end-use testing/capability studies)
  • Receding angle / hysteresis characterization (this workflow is centered on water contact angle for treatment verification)
  • Direct measurement of liquid surface tension (this is not a tensiometry method)
  • Surfaces with strong chemical affinity for water (ISO notes the method is not applicable in this case)

Minimum you must report (checklist)

  • Film identification: polymer type, structure (mono/multi-layer), surface side tested, and any additives/coatings/primers if known
  • Treatment history: corona/plasma/primer details (if available) and time since treatment (including any storage/aging conditions)
  • Test liquid: DI water (grade/source) and any conditioning steps (e.g., temperature equilibration)
  • Environmental conditions: temperature and relative humidity during test
  • Instrument & method: goniometer/drop shape analysis approach, calculation/fit method, and any software version if applicable
  • Drop parameters: droplet volume, dispense method/needle, and time window used to read/report θ (define your SOP timing)
  • Results & statistics: θ per zone plus summary statistics (e.g., median + IQR or mean ± SD), pass/monitor/fail limits used, and optional γc reported as “derived from ISO conversion chart” if included

Note: Water contact angle is a strong, QC-friendly indicator of surface wetting and treatment consistency, but it is not, by itself, a complete measure of adhesion or print durability. Acceptance limits should be established per film family and end-use via capability studies that correlate θ to real outcomes (ink adhesion, rub resistance, lamination bond strength, etc.).

How to interpret results (guardrails)

  • Treatment level (common practical guide for many low-energy films): θ > 90° marginal/no treatment; 85-90° low; 78-84° medium; 71-77° high; < 71° very high.
  • “Lower θ = better wetting” decision rule: A flatter drop (lower θ) generally indicates higher treatment and lower risk of wetting-related print/bond defects (for polar interfaces).
  • Uniformity matters as much as the average: Treat edge-to-center differences and large spreads as process signals (nonuniform corona, contamination, handling, or aging), not “noise.”
  • Use θ as the primary QC metric; validate performance separately: If customers specify dynes, you may report γc from the ISO chart as a continuity metric, but keep θ primary and confirm adhesion with product-specific testing.
Read our ASTM D5946 / ISO 15989 page View the official ASTM D5946 Standard

Now It’s Your Turn

We hope this guide showed you how to apply surface science in the Food & Beverages industry.

Now we’d like to turn it over to you: 

  • What’s the #1 real-world application from this post that you want to try first?
  • Perhaps we missed a relevant industry standard.
  • Or maybe you have a question about something you read.

Feel free to leave a comment below—we’d love to hear from you.

Frequently asked questions

Which surface measurement should a food lab start with?

Start with the problem. Use interfacial tension for emulsions, and surface tension for foams, beverages and coating liquids. Use contact angle when a coating, cleaner or package meets a solid surface, such as a peel or a film. Surface free energy comes from contact angles of two or more probe liquids. Our surface tension and contact angle guides explain each method.

Can I measure how an edible coating wets fruit skin?

Yes. Measure the coating surface tension by pendant drop, then the contact angles of probe liquids on the peel to work out its surface free energy. The Research Institute for Bioscience and Biotechnology in Nepal used this approach to compare edible coatings for tomatoes. Read the RIBB edible coatings case study. Peel values vary with cultivar, ripeness and washing, so test matched samples.

How do I screen emulsifiers for creams, sauces and dressings?

Measure oil and water interfacial tension for each emulsifier across a concentration range, at a fixed temperature and drop age. Lower tension is a useful screen, but it does not guarantee stability, so storage tests are still needed. University of Waterloo researchers measured surface tension of zein protein dispersions in food thickeners and suggest them for egg free mayonnaise.

Can the Dropometer measure interfacial tension between two liquids?

Yes. A drop of one liquid is formed inside the other, and the drop shape gives the interfacial tension. You need the density of both liquids at the test temperature. Users of a shared facility at Harvard University run this mode, including a study of capsules for controlled delivery that found lower tension alone did not explain stability.

Can contact angle verify cleaning of food contact surfaces?

It can flag residues that other checks miss. A higher water contact angle than on a clean reference suggests an oily or fatty film remains, even when ATP results pass. It does not detect microorganisms or prove a surface is sanitary, and it may miss residues that wet well. See surface cleanliness and hygiene verification.

Which standards apply to wetting in food and beverage work?

ASTM D5946 and ISO 15989 describe water contact angle on corona treated polymer film, a common packaging material. The Dropometer measures static water contact angle by the sessile drop method. No published wetting standard covers edible coatings, food emulsions or beverage foam. For those, write your own method and record liquid, temperature, drop volume and drop age.

How accurate is the Dropometer?

The drop shape method was validated against a KRUSS DSA100E in two peer reviewed papers, one in Review of Scientific Instruments and one in Colloids and Surfaces A. Published contact angle accuracy is 0.35 degrees. Automatic edge and baseline detection gives the same reading from the same image. See our validation papers.

Do published food and water studies use the Dropometer?

Yes. Food scientists have measured water contact angle on bio based films from corncob, alfalfa and carrageenan, alfalfa lignocellulose and soyhull lignocellulose. A Concordia University thesis used it to choose marker inks for a paper based water hardness test, also published as a journal paper. See all client citations.

Standards, evidence and resources

1. Use cases Case studies Client citations (our analysis of each paper) Use case collections Further resources