Why coffee with milk feels different: a new study examines the mixture

A study published in npj Science of Food on 30 September 2026 describes how the milk matrix changes structure and friction in coffee–milk mixtures. Milk proteins and coffee constituents can form aggregates; fat also affects these structures. The findings help explain mouthfeel more precisely, but do not provide a universal ranking of the best milk for coffee.

Which types of milk were studied

The team prepared 4 coffee–milk systems: with ultra-high-temperature or pasteurised whole or skim milk. They examined physicochemical properties, friction behaviour and sensory properties. The comparison concerns cow’s milk and the selected mixtures.

That choice matters when interpreting the findings. Different coffee, mixing ratios or plant-based drinks may behave differently. The public abstract gives no universal milk quantity for a particularly creamy cup.

What happens to structure during mixing

Adding milk increased pH, lightness, viscosity and particle size, among other properties. Electron microscopy showed aggregates. Changes in spectroscopic measurements added evidence of structural reorganisation in the mixture.

Molecular simulations mainly suggested hydrogen bonding and interactions between aromatic molecular structures as connections between coffee constituents and milk proteins. This offers a mechanistic explanation; calculations alone do not prove how every possible cup tastes.

Thickness and lubrication are different properties

The structural changes studied strengthened interactions between particles and reduced lubrication at interfaces. Friction coefficients increased. The work therefore illustrates why greater viscosity does not automatically mean less friction.

Fat, conversely, disrupted aggregate structures and reduced friction; experiments in which fat was added back supported this connection. These measurements describe different properties of a drink. Understanding your own mouthfeel experience requires considering both composition and personal perception.

What the report leaves unresolved

The publisher is initially providing a peer-reviewed early version that may still undergo editorial changes. This article uses the public abstract and bibliographic details. It does not add unavailable friction values, tasting scores or sensory panel sizes.

The results support neither a health claim for milky coffee nor equivalence with oat, soya or pea drinks. Frothing is a separate question too: the new work explains the mixture and its friction behaviour, rather than providing a general guide to perfect milk foam.

Choose milk for the result you want

The German Federal Centre for Nutrition describes fat as a flavour carrier and the choice of fat content largely as a matter of taste. Its kitchen information says both reduced-fat and whole milk can be frothed, although reduced-fat milk produces less creamy foam. This is background on frothing, not a finding from the new study.

When comparing milk types, distinguish flavour, mouthfeel and foam. A product may appeal on one criterion and less on another. Personal preference and the intended preparation are more useful than a blanket judgement based on fat content.

A simple comparison for your own cup

• Use the same freshly prepared coffee and divide it between comparable cups.
• Add equal quantities of milk and keep drinking temperatures as similar as possible, so several changes do not act at once.
• Assess aroma, bitterness and mouthfeel separately. Record your impressions rather than turning them into a general product rating.
• If you also want to froth the milk, test that separately and follow your equipment’s instructions.

The German Federal Centre for Nutrition points out that brewing method, grind size and fresh preparation also affect coffee flavour. Our breakfast recipes and recipes by ingredient provide meal ideas to go with it. The cup comparison is an editorial kitchen suggestion, not a reproduction of the laboratory experiment.

Conclusion: the whole mixture matters

The new study shows that milk changes more than coffee’s colour. Protein aggregates and fat influence structure and friction in different ways. For the kitchen, this suggests a useful comparison: keep coffee, quantities and temperature as consistent as possible and assess which milk suits your preparation.

Sources and update

• Wu et al., npj Science of Food: study of milk matrix, friction and sensory perception in coffee–milk systems, published on 30 September 2026; peer-reviewed early version.
• German Federal Centre for Nutrition: milk, from shopping to the kitchen; background on fat content, flavour and milk foam.
• German Federal Centre for Nutrition: coffee, from shopping to the kitchen; background on fresh preparation and brewing methods.

Author: Kochzauber editorial team. Information updated on 30 September 2026. This article explains food texture and does not assess the health effects of individual drinks. The cover is an editorial symbolic image.