Category: MSci Project 2014/15

The Relationship between Structure and Crispness

Last week we began measurements on McVitie’s Digestive biscuits and carrots. We steamed the samples for different periods of time in order to modify their moisture content. We chose these two foods because of their very different structures. We want to probe how the moisture dependencies of acoustic and mechanical parameters are influenced by structure.

We steamed biscuits for 30, 45 and 60 seconds and carrots for 1,2,3,4 and 5 minutes in a steam oven. The acoustic data was consistently limited for different steam-time samples in both foods and failed to give any useful information. However, the force-deformation curves were more successful for both foods and we were able to identify parameters in each that showed a dependency on steam time.

Literature Review on Existing Acoustic-Mechanical Research

Up until recently our project has focused on engineering an acoustic-mechanical texture analysing device. As Leon mentioned in his last post, we have now completed the construction of the device and, over the past couple of months, have been carrying out preliminary measurements. During the data acquisition and analysis process, we have drew heavily on existing research. The picture below links to my review of all the pre-existing literature concerning acoustic-mechanical measures of crispness.

In my first post I discussed how there was a sparsity in existing research with regards to quantifying crispness in crusted foods with high-moisture cores (e.g.

Preliminary Acoustic Measurements – Pringles

Acoustic data was acquired using the program Audacity at the standard sampling frequency 44100Hz, producing signals showing sound pressure level (SPL) over time. Background noise was removed by subtracting the noise profile from the signal. Different noise reduction levels were trialled on an example signal (see below) and a 48dB reduction proved most effective.

A Fast Fourier Transform (FFT) was computed on the signal to translate it to the frequency space. A Hanning window function was used for the spectrum and different sizes of FFT (number of frequency bins) were trialled to see which gave the most suitable frequency resolution (see first diagram below).

Trial Measurements and Data Handling

Our measuring instrument is a guillotine like device that we can use to break chips. For now we practiced with dry spaghetti as they are less messy and easily accessible. The two sensors we use are a load cell at the tooth of our guillotine to measure the force and a potentiometer to measure the displacement change as we move down. We filter the signal from the load cell using a self-made instrumentational amplifier and measure the voltages with an oscilloscope.

The photo of the oscilloscope output below shows a typical measurement outcome when breaking the spaghetti. The blue channel is proportional to the displacement while the yellow channel represents the force on the spaghetti.

Introduction and Summary of the Literature Review

Hi, my name is Léon and I am one of the students working on the physics of cooking project this year. We have had some problems with ICT and I have been meaning to post for a while since we have made a lot of progress. I think the best introduction to our work would probably be a quick summary of my literature review to give you an idea of the field in general.

I was quite surprised about the amount of literature on frying potatoes and about food in general. Scientists from all kinds of backgrounds have successfully applied objective methods and carefully thought through theories to cooking.

Food Research for 2014/15

Leon van Riesen-Haupt and I are working on an MSci Project with Prof. Peter Török and Dr. Carl Paterson on the physics of cooking and will be sharing our progress through this blog for the rest of the academic year.

There are many interesting research topics when it comes to the physics of cooking and is demonstrated well by the breadth of the research already conducted by previous MSci students. Echoing previous research, the initial aim of our work was to define experimentally and/or theoretically what constitutes the perfect French fry. Now many a chef will tell you that it has to be a perfect balance of a crispy, glassy exterior with a fluffy, light interior, but what is the underlying physics from which this sensory perception emerges?