Week 2 – Process Flow Diagram and Calibration Curve

For week 2, we had to set operating parameters for each of our equipment and relate it to coffee brewing. Below is our updated process flow diagram from week 1, which lists each equipment’s operating parameters. These parameters include temperature, flow rate, composition, and particle size. It was hard to find information on some of the equipment, so some parameters were estimated based on how the equipment operates.

Name of your manufacturing process: Lycopene Extraction from Tomatoes
Name of your final product: Lycopene extract

Figure 1: Process Flow Diagram

Experiments with coffee extraction could be used to determine where to set these parameters. For example, to find the optimal particle size, we can grind coffee beans into different sizes, then leach the coffee solubles with water through a paper coffee filter.  We could compare the starting mass of the coffee beans with the concentration of the coffee to determine the efficiency of the extraction. However, if the coffee bean grind is too large, then that may obstruct the coffee solubles from being picked up by the water and flowing through the filter, lowering the efficiency.  If the grind is too small, then nothing will get filtered out, causing the coffee to be highly concentrated, but contaminated with coffee grounds, which we don’t want.

Another example would be finding the optimal flow rate by using coffee filters that are made of different materials. The material that the filters are made of contributes to how big the pores in the filter are and how many pores there are. If the pores were small and not many existed in the filter, then the flow rate of the coffee will be slow. If the pores were big and many existed in the filter, then the flow rate will be fast. Therefore, we can test out different coffee filters to see what the optimal flow rate would be (supplementary article). However, the material of the filter may not be strong enough to hold a sufficient amount of ground coffee beans. The filter may also be very thin and bad quality, which could make the grounded coffee go straight into the cup without filtering it. Another error could be that the filter doesn’t have enough pores for the coffee to drip into the cup, resulting in no liquid coffee at all.

An analytical technique that we thought could be used to measure coffee concentration was using serial dilution. We can use this to create a series of solutions of different concentrations varying by a constant dilution factor, then measuring the conductivity of each of them to plot a conductivity calibration curve.  The conductivity of a solution with unknown concentration is measured and compared with the conductivity calibration curve.
Pros: Probe to measure conductivity is cheap, the concentrations of coffee will probably make the conductivity of trace elements in water insignificant.
Cons: Conductivity is also positively correlated to temperature, so we have to wait for solutions to reach the same temperature before measuring conductivity (article: common mistakes when measuring conductivity). Error in serial dilution will propagate to the rest of the solutions.

Calibration curves

Below is one of our group member’s calibration curve from this week’s lab activities. We had to measure the conductivity of different coffee concentrations. From the curve, we can see that as the concentration increases, the conductivity increases.


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