Food poisoning is a serious issue for manufactures during hot seasons. Sterilization before packaging is the favored practice, but high temperature treatments are not possible for some drinks such as dairy products.
Deterioration of drinks can be estimated by culturing bacteria, but it may take long time (e.g. one day) after sampling on culturing medium, and it is apparently not feasible to apply this method in order to screen all the drinking products. ViscoWave is an easy remote sensing solution to screen drinking products as viscosity of liquids may change as it degrades.
Step 1: Sample Preparation
After opening a bottled milk tea, the liquid was exposed to ambient air for one hour; floating bacteria were introduced into the liquid.
Step 2: Counting bacteria and Viscosity Measurement
ViscoWave was used to determine viscosity of the 15mL sample. Temperature of liquid was set to an ambient temperature. On the other hand, counting bacteria in the liquid using the culturing method was also performed. The sample medium was stored in an incubator at 37C for 24 hours before counting bacteria.
Step 3: Repeat the above procedures for days.
Results are shown in the plot. Virtually no bacteria was detected on the first and the second days (dotted line) while rapid increase was observed in the following days. Measured values by ViscoWave on the day were also decreased indicating higher viscosity of the liquid. It is interesting to note that apparent value changes were observed in ViscoWave in the first two days when very little bacteria increase was observed.
In this experiment, drip from unfrozen meat, containing many bacteria, was introduced into a PET bottle of the same kind. ViscoWave data was taken in the following days.
Similar results were observed until the second day as shown in the plot. Viscosity was significantly increased on the third day, and the value was reduced again on the fourth day. Solid separation in the liquid due to degradation may cause reduced viscosity in the remaining liquid.
Viscosity changes measured using ViscoWave caused by deterioration of drinking liquid were examined. Small bacteria increase can be detected with ViscowWave. Number of bacteria in the liquid is not directly related to the ViscoWave value, but the measured values are an interesting indicative of liquid deteriorating process. It is important to note that the measurement has been done without touching the liquid directly; the technology may be applied to check integrity of drinking liquids.