Food Science Calculations: Shelf Life, Q10, Water Activity & Microbial Growth

What you'll build

What you will be able to do

Each lab ends with a concrete result that you build yourself and the checker confirms, cell by cell.

• Fit the vitamin C loss of Brightfield orange juice stored at 25 °C: take ln C, find the rate constant k as the negative SLOPE, the half-life, and plot the straight line.
• Turn the rate constants into a shelf life: days until vitamin C reaches the label claim, days until browning is rejected, the attribute that fails first and a labelled shelf life with a safety margin.
• Take the rate constants measured in a hot accelerated test, calculate Q10 and predict k and the shelf life at chilled and ambient storage temperatures.
• Turn four rate constants of the juice into an Arrhenius plot: kelvin, 1/T and ln k, the slope, the activation energy Ea and a predicted k at 20 °C from the fitted line.
• Convert the moisture of Brightfield crackers to dry basis, look up their water activity in a sorption table, find the critical moisture for crispness and the days until the pack lets in enough water to soften them.
• Model spoilage bacteria in a Brightfield ready meal held at 8 °C: log counts, the specific growth rate from the doubling time, the time to reach the spoilage limit and a log-count table with a lag phase.
• Check the sterilisation of a Brightfield canned soup from its cold-spot temperature log: lethal rates, the F0 value by the general method, the log reductions and the D-value at a lower temperature.
• Pull the course together for the product file: k and the shelf life at 4, 20 and 30 °C, a weekly prediction table for a year and a line chart against the label claim.