Tribology

Overview

Fat contributes to taste, flavour, texture and mouthfeel of dairy foods, therefore reducing or omitting fat generally leads to defects in texture and mouthfeel of dairy products. Many fat replacers have been introduced to improve the texture and mouthfeel of no-fat and low-fat products.

Assessing mouthfeel attributes, especially those related to fat perception, is traditionally performed by a trained panel, which is time-consuming and can vary considerably. Therefore, assessing the lubrication properties of food by using a quick and simple tribology test will not only allow the food and beverage industry to screen newly developed products but also products undergoing formulation.

This project aims to investigate the lubrication behaviour of a variety of dairy products including fluid milk, flavoured milk, yoghurt, custard, cream cheese and dairy spreads focusing on the effect of fat content, type and level of fat replacers. The lubrication behaviour will be compared and correlated with the sensory mouthfeel perception from a sensory panel.

Capabilities and technologies

Tribometer and tribo-rheometry

The tribometer is set up by attaching a tribo-rheometry into Discovery Hybrid Rheometer (TA Instrument, USA) (Figure 1a). Two types of tribo-rheometry have been used:

  • A half ring on a plate tribo-rheometry, which is suitable for liquid and semi-solid fluids (milk, yoghurt, cream cheese) on elastic surfaces (Figures 1b–1c).
  • A three balls on a plate tribo-rheometry, which is suitable for semi-solid fluids and solids (cream cheese, butter) on stiff surfaces (Figure 1d).

 The lower plate can be replaced by a sample cup for liquid samples (Figure 1e).

Figure 1. (a) Tribometer, (b)–(c) half ring on a plate tribo-rheometry, (d) three balls on a plate tribo-rheometry, and (e) sample cup tribo-rheometry for liquid samples.

Sensory

The Tribology research team makes use of the Food Sensory Laboratory, a teaching, research, training and service unit within the School of Agriculture and Food Science at The University of Queensland. The facility is well-suited for controlled sensory evaluation of food and beverages by trained and semi-trained panels.

The panel tasting area contains five individual tasting booths, each equipped with a computer for data collection using Compusense® Five software (Figure 2). The tasting area is equipped with lighting of variable intensity and colour, control of air temperature and flow. A kitchen and meeting room adjoining the tasting area are used for sample preparation and panel training.

Figure 2. Tasting booths equipped with computers for data collection in the sensory lab.

Outcomes

The project has:

  • Further investigated the setup of the tribometer and established that the methodology can differentiate between dairy products of differing fat content: pasteurised milk (0.1–5% fat), chocolate milk (0.8–3.4% fat), yoghurt (0.1–9.7% fat) and cream cheese (0.5–11% fat).
  • Investigated the effects of solid surfaces, such as silicone rubber, ethylene propylene diene monomer (EPDM) rubber, surgical tape (Figure 3a) and whey protein gel (Figure 3b) to assess the best replicate surface of the tongue when used in tribology measurements. Surgical tape has been found to be the best surface for dairy tribology measurements among the four.
Figure 3. Different surfaces have been used as a tongue model for tribology measurements. (a) Silicone rubber (blue), EPDM rubber (black) and surgical tape (white) and (b) whey protein gel.
  • Developed and produced in-house dairy products, such as yoghurt, chocolate milk, custard and cream cheese, containing different fat contents and fat replacers.  A satisfactory correlation has been established between the tribology and sensory data that will enable future use of tribology as a tool for product development by the dairy manufacturing industry.

Publications

Godoi, F. C., Bhandari, B. & Prakash, S. (2017). Tribo-rheology and sensory analysis of a dairy semi-solid. Food Hydrocolloids, 70, 240–250.

Nguyen, P. T. M., Kravchuk, O., Bhandari, B. & Prakash, S. (2017). Effect of different hydrocolloids on texture, rheology, tribology and sensory perception of texture and mouthfeel of low-fat pot-set yoghurt. Journal of Food Hydrocolloids. (Under revision).

Nguyen, P. T. M., Nguyen, T. A. H., Bhandari, B. & Prakash, S. (2016). Comparison of solid substrates to differentiate the lubrication property of dairy fluids by tribological measurement. Journal of Food Engineering, 185, 1–8.

Nguyen, P. T. M., Bhandari, B. & Prakash, S. (2016). Tribological method to measure lubricating properties of dairy products. Journal of Food Engineering, 168, 27–34.

Researchers

  • Dr Sangeeta Prakash

    Chief Investigator

  • Jia Zhao

    Masters Student

  • Amy Lalruatdiki

    Masters Student