Blog posts

Potato density changes with age – by Karim Bahsoon

Potato density vs Age (expiration date of potatoes 1st March 2011)

As discussed we have been measuring the density change of the potato over a number of days. The potato was left out at room temperature and the density measurements were carried out using the same method as before (filling measuring jug with water to assess volume/mass change).

DATE MASS (g) VOLUME DISPLACED (ml) DAYS AFTER EXPIRY DENSITY (g/ml) 24/02/11 142 130 -5 1.092307692 25/02/11 142 130 -4 1.092307692 28/02/11 140 129 -1 1.085271318 01/03/11 140 129 0 1.085271318 03/03/11 139 129 2 1.07751938 07/03/11 138 128 6 1.078125

The density change has been fairly minimal, and the precision of the scale (accurate to 1 gram) has perhaps hindered the experiment somewhat.

Starch concentration measurement in potatoes – by Jason Chang

New density measurements and Calibration

As advised from the last meeting we placed the measuring jug on an electronic scale, reset the scale to zero and filled it with 400g worth of water. We found that there was a small error in the jug which produced the systematic errors in our previous measurements. We marked the real 400ml mark with a pen and took new volume and weight measurements. I also skinned two of the potatoes to check the removal of skin didn’t significantly change the density (The rows highlighted in the same colour correspond to the same potato). Below is a table of results of potatoes with the skin on:

Measuring the density of french fries

As part of his MSci project Karim Bahsoon has been investigating the effects of varying blanching time on the properties of french fries. Jason Chang, who works with Karim, is involved in measuring surface starch content and crunchiness of the ready chips.

Potatoes were cut into fries and placed in boiling water for times varying from 0-12 minutes. These were then submerged in vegetable oil at 170C for 4 minutes and then fried again at a higher temperature of 190C for a further 2 minutes. The second fry is thought to help with crust formation and adds to the crunchiness of the fries.

FoodCycle charity event with Tom Aikens

Imperial College FoodCycle is organising a charity dinner cooked by Tom Aikens. It will be held on the 21 March 2011 at Whole Foods Market, High Street Kensington. FoodCycle is an organisation that uses raw food ingredients donated by various supermarkets and other suppliers, that would otherwise be wasted, to cook meals for people who cannot afford a hot meal. An excellent example to follow!

Chocolate mousse with Tom Aikens

As a part of the MSci project on Cooking a Steak, we would like to communicate the physics and those physical processes that take place during cooking to the general public. Karim Bahsoon and Jason Chang are the two fourth year undergraduate students working on this project.

The dessert course of the menu will be a chocolate mousse by Tom Aikens. Tom is a Visiting Researcher at the Physics Department and he has been advising us on the menu. In addition to his help Tom actually cooked all the courses for us so that we know how the original versions taste.

First paper on Food Research has been submitted

Yesterday we submitted our first paper on food research to Journal of Food Engineering entitled “Tenderising effect of sodium bicarbonate on pork loin”. The paper is based on the work Xiao Liu Chu has done on comparing the effect of sodium bicarbonate with sodium chloride solution (brine). The authors are XL Chu, P. Török, C. Paterson, Tom Aikens. Here is the abstract of the paper:

“We investigated the effect of a 3% concentration solution of sodium bicarbonate (treatment A) and pure sodium bicarbonate (treatment B) on pork loin samples. These were compared to a 5% salt brine (treatment C), controls consisting of tap water (treatment D), and untreated samples (treatment E).

Discussions with Dr Baranyi at the Institute of Food Research

I have visited Dr József Baranyi, leader of the Computational Microbiology Research Group at BBSRC’s Institute of Food Research to discuss possible collaboration on predictive microbiology. We have strong interests in developing reliable ways of constructing models for non-isothermal predictive microbiology. Currently population level modelling is based on first order kinetics for both growth and inactivation. This model however, is only applicable on a very limited and constant temperature range. Both professional and home cooking, on the other hand, take raw food ingredients through rather complicated heat cycles which in turn violate the validity conditions of the model. We have two fourth year undergraduate students, Sergey Goryunov and Vedish Bhatoolaul, working on this project.