Things change, food goes hard, food goes soft and food goes off. What I love to do is to find out why and how. Right down to the molecules and the atoms. Magnetic resonance is a great non-destructive way of finding out why and how materials change. We can see if molecules slow down, speed up or interact with others. A lot of food is solid so solid-state magnetic resonance is a handy way of studying the physics of food. Magnetic resonance micro-imaging offers a means of observing changes on the macro-scale. Also, under the guidance of Dr Tuoc Trinh, I'm expanding into the world of non-newtonian fluids. On this page I've put a little smorgasbord of samples of my of research. Below is a photo of the Solid-State NMR and Magnetic Resonance Micro-Imaging Instrument at Massey University Palmerston North. I have put the instrument together over the years with the help of a lot of generous people (2006 and 2012).
To increase protein content, a range milk proteins were added to baked starch snack bars. Formulation trials found different proteins produced bars of significantly different textures. Whey protein isolate (WPI) produced the hardest whereas milk protein concentrate (MPC; approx 80% casein and 20% whey proteins) the softest. To found out why, solid-state carbon NMR was used to observe the state of the starch. In the figure is the solid-state carbon NMR spectra of model baked starch bars, containing 100% starch or either 20 wt% WPI or MPC. The peaks labeled C1 to C6 represent the carbons on glucose unit in the starch chains. The shape of the C1 peak is sensitive to the angle and mobility of glucose unit interlocking bonds. The changed shaped of the C1 peak showed the WPC produced a harder bar because it interacted with the starch chains. Reducing the starch degree of freedom of movement around the C1 carbons. This was the final year research project of Food Technology student Wong Xin Yu.
For some people peanut butter and chocolate is a delicious combination. For a food technologist it can be a nightmare. The low molecular weight oils in the peanut butter can diffusion into the chocolate during storage. The oil softens the chocolate to a point where it becomes unacceptable to consumers. The oil redistribution can be reduced with either reformulation of the peanut butter or by placing a barrier between the peanut butter and chocolate. In this study, a number of methods to minimise oil redistribution were trailed. Magnetic resonance imaging offered an excellent non-destructive technique to monitor the hardness of the chocolate during storage. Internal images can be taken so the intensity of the image is directly related to the hardness of the material. On day 1, the outer layer of chocolate is not observed. It is too hard to be detected. By day 20, oils from the peanut butter have diffused into the chocolate, softening it to a point where it can be seen. This was the final year research project of Food Technology student Gabrielle Cooper.
Where does the cellular signalling process which initiates ripening in fruit start from? To observe this in feijoa three dimensional time lapse MRI images were taken of feijoas. The images were encoded to highlight the comparative hardness of the feijoa flesh. In the MRI image, the red colour is the location of softest flesh inside the feijoa. Time lapse images show the gradual softening (ripening) of the feijoa initiates and grows from around the seeds.
Updated 5 March 2015