Thermal behavior of vegetable fat spreads (margarines)

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          RHEOLASER Crystal

 

 rheolasercrystal


Application
Food


 Introduction

Butter, margarine and vegetable fat spread are water in fat emulsions (milk-based for butter and other matrix for margarines and oil spreads), in which some of the fats are crystallized. They are used for many applications (cooking, spread, pastry…).

Depending on end-use, manufacturers modify the formulation or the process to adapt the melting temperature.
Because of the sensitivity of fat crystals, it may be difficult to control the melting temperature without denaturation of the product with traditional thermal analysis (DSC, Micro-DSC…), as crystal structures are sensible to shearing force.
In this application note, we used the Rheolaser Crystal, to monitor melting properties of margarines.


 Objective

Measure the melting properties of margarines


Device

Rheolaser Crystal


 

Reminder on the technique 
RHEOLASER Crystal uses the DWS principle. 

graph1Light is scattered by the particles, creating an interference pattern (Speckle Image). The variation of this image is related to the motion of the particles. By a mathematical analysis of this variation, decorrelation functions can be calculated and then processed, to obtain a characteristic time τ as a function of time or temperature.
Values of 1/τ or Micro-Dynamics (Hz), are then plotted against time or temperature, resulting in characteristic peaks when the product shows a microstructural evolution, such as a phase transition or any other physical event. The signal can then be integrated for an easier visualisation, obtaining the so-called Micro-Dynamics Evolution (%).

 

 Method

For these tests, four samples were analyzed:
- A vegetable fat spread (55% of fat)
- Unsalted butter (82% of fat)
- Cook vegetable fat (70% of fat)
- Light butter (41% of fat)
Samples of approximately 2 grams were heated from 4°C to 80°C at 5 °C/min
Micro-Dynamics in function of temperature was monitored, peaks representing polymorphic transition in the sample (melting mostly).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

rheolaser crystal175 225

 Experimental Results

1) Differences in function of end-usedfig1
First, we compared three types of fats. One used for spread (light butter), one used exclusively for cooking (cook butter), the last one being a common butter.
Principal melting peaks are not localized at same temperatures. Cook butter (in green) has a high Melting temperature (40°C). Light butter have the lowest melting temperature (30°C). For cook butter the high melting temperature guarantee a better behavior at elevated temperature, useful for cooking. The low melting temperature of light butter ensure a better spreadability. Unsalted butter shows an intermediary behavior.
An representatice amount of sample was used (2 grams) to avoid denaturation and to analyze a representative part of the product (which may be heterogeneous).

 

2) Differences in function of formulations
dfig2Two margrines are compared, with the same end-use (spreading) but with different formulations.
In figure 2, the two samples have the same peaks at 30°C and 35°C.
Formulation between vegetable fat spread and light butter were very different (vegetable fat versus milk fat, different percentages of fat…), but manufacturers create fat spread with almost the same melting behaviors.
They can adjust melting properties with formulation but also with process, that’s why it is crucial to preserve the original structure during sampling prior to analysis.

 

 

 

 

Rheolaser Crystal offers:

VERSATILE – Any sample form (liquid, solid…) and structure (heterogeneous, multi components…)

ACCURATE - nano-scale sensitivity, large sample, direct sampling with no denaturation

NO STRESS – analize fragile samples without changing the crystalline structure

 

Summary

With the RHEOLASER Crystal we can obtain crucial information about melting properties of products like butter.
Crystallized fat emulsions possess a delicate structure, which may be denatured during sampling with other techniques. In RHEOLASER Crystal we can use a great quantity of product (up to 4 grams), so it’s easy to preserve the initial properties of products.
RHEOLASER CRYSTAL can discriminate butter and oil spread in function of their melting properties, but can also be used to analyze the impact of a new raw material on melting temperatures.

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