Can a spectrometer be used to figure out spice ratios in a sauce?
Unfortunately, this will not even qualitatively work because taste which is a sense of perception and UV-Vis are barely related.. The USB spectrometer would be great for color matching, but you are assuming the taste and aroma comes from UV-Vis absorbing compounds only. This may not be the case. Let us assume, the taste comes from UV-Vis absorbing compounds, as you know from Beer's law, an $n$-component mixture will have  absorbance sum from $n$-components. If some of these molecules are in trace quantities, they might have a little effect on the overall spectrum but they might have a huge influence on the taste and aroma of your sauce. Food chemists prefer more of gas chromatography and mass spectrometry &amp; infrared spectrometer which may cost more than 100K.