Absorption spectra of different chocolates
Did you know? These knowledge about 'chocolate'
Valentine's DayIt is one of the national and global holidays. This romantic festival began around the 14th century and is a celebration of love by exchanging affectionate greetings and gifts. The well-known gifts include fragrant flowers and sweet and delicious oneschocolateAlthough the term 'chocolate' encompasses a wide range of candy categories, its definition is very strict for certain specific types of chocolate. Anything defined asMilk chocolateAll chocolates must contain cocoa butter, cocoa solids, at least12% milkand10% cocoa.
This is justMilk chocolateThe limit indicator is that high-quality milk chocolate generally contains30-40% cocoaThe remaining ingredients may be sugar, vanilla, emulsifiers, and other seasonings.White chocolateMust contain at least14% milkand20% cocoaBut it does not contain cocoa solids, which can eliminate the fruity and bitter flavors of chocolate itself.
Dark chocolateIt must contain at least35% cocoaIn general, this ratio is close to60-70%, up to a maximum of90%Left and right, the regulations require no milk, but there is usually a trace amount of milk.
Usually, these different types of chocolate can be distinguished by visible colors and materials to the naked eye. But we can also distinguish them based on their composition - that is, their molecular composition. In this experiment, we will useNear infrared spectroscopyTo achieve.
Figure 1: Five types used in the experiment
Chocolate sample and white reference
From left to right: milk chocolate, cheap milk chocolate, white chocolate, dark chocolate with a cocoa content of 78%, dark chocolate with a cocoa content of 92%, Avantes' white reference tile (WS-2).
The spectrometer used in this experiment (Figure 2) isAvaSpec-NIR256-1.7-EVONear infrared fiber optic spectrometer. This near-infrared spectrometer has a measurement range of up to1.7 μmUsing a high-sensitivity optical platform with excellent performance parameters, the sampling speed can reach0.53 msThe integration time can be as short as10μs.
Figure 2: AvaSpec-NIR256-1.7-EVO (left), integrating sphere and chocolate sample (right)
AvaSpec-NIR256-1.7-EVO is equipped withInGaAs (indium gallium arsenide)Array detector,USB3andGigE VisionThe ultra-low noise circuit board. You can choose different gratings and slits. The digital and analog I/O interfaces of the spectrometer can achieve external triggering of the spectrometer and control of the pulse light source and shutter, and can be selected through softwaretwo kindsDifferent gain modes, namely high sensitivity mode (HS, default) and low noise (LN) mode.
The light source used in this experiment isAvaSphere-50-LS-HAL-12VIntegral sphere with built-in halogen light source (Figure 3). This point ball is designed specifically forreflectionDesigned for practical applications, but also suitable for low reflective materials and near-infrared spectroscopy measurements.
Figure 3:AvaSphere-50-LS-HAL
-Within 12VPlace halogen lamp light source
Integral sphere with built-in halogen light source provides samplesDiffuse halogen light, which can avoid losses related to fiber coupling. Compared with our standard reflective integrating sphere, the illumination intensity on the sample is as high as160Twice. AvaSphere-50-LS-HAL-12V Integral SphereThe inner diameter is 50mmThere is a 10mm diameter sampling port, an SMA reference port, and a collimated SMA port used to collect signals from the AvaSpec spectrometer.
Other accessories used in this experiment include:
A glass separating the chocolate sample from the integrating sphere
White reference tile (WS-2), used as a reference to compare each chocolate sample
600 micron core fiber (FC-UVIR600-1-BX), connecting integrating sphere and spectrometer
Except for the cheap milk chocolate sample which is a separate piece of chocolate, each chocolate sample is broken off from a complete piece of chocolate. Each sample is stored in a drawer at around 21 ℃ to ensure that the chocolate does not melt. When measuring, each chocolate sample is first placed on a glass slide, and then the slide is placed on the sample port of the integrating sphere (Figure 4).
Figure 4: Separating the integrating sphere and chocolate with glass
This glass can prevent chocolate chips from entering the integrating sphere and causing pollution, while also making the measurement distance more consistent and obtaining more accurate results. Firstly, measure the white reference porcelain as our white reference and place it on the glass to ensure consistency in the measurement distance.
We use the AvaSoft softwareT-absorptionDegree mode, with its counting unit beingA.U.AvaSoft is our customized data analysis software package. This mode is specifically designed for absorbance applications. In this experiment, we will use a white reference tile as the white reference. Translate into Englishintegration timeSet to around 3ms, the integration time can increase or decrease the amount of light measured once, affecting the overall amplitude of the measured spectrum. We willaverage frequencySetting it to 100 means averaging 100 values together to provide more consistent spectral results. When the integration time is short, a higher average frequency can be used.
The spectrum obtained from the experiment is shown in the following figure
Figure 5: Absorption spectra of milk chocolate samples
The peak values are at 1209.81 nm and 1437.32 nm, with absorbance values of 0.50 A.U. and 0.74 A.U., respectively
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Figure 6: Absorption spectra of cheap milk chocolate samples
The peak values are at 1209.81 nm and 1437.32 nm, with corresponding absorbance values of 0.52 A.U. and 0.79 A.U., respectively
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Figure 7: Absorption spectrum of white chocolate sample
The peak values are at 1209.81 nm and 1437.32 nm, with corresponding absorbance values of 0.52 A.U. and 0.79 A.U., respectively
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Figure 8: Cocoa content of 78%
Absorption spectra of dark chocolate samples
The peak values are at 1209.81 nm and 1437.32 nm, with corresponding absorbance values of 0.53 A.U. and 0.68 A.U., respectively
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Figure 9: Cocoa content of 92%
Absorption spectra of dark chocolate samples
The peak values are at 1128.26 nm and 1322.60 nm, with corresponding absorbance values of 0.52 A.U. and 0.62 A.U., respectively
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Figure 10: Comparison of Results
Milk chocolate sample(Blue)Cheap milk chocolate samplesredWhite chocolate sample(Light green)Dark chocolate sample with a cocoa content of 78%(Dark red)Black chocolate sample with a cocoa content of 92%(Dark green)The absorption spectrum
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The absorption spectra of all chocolate samples are within1209.81 nmand1437.32 nmPeak value was measured at the location.
Data Description:The absorbance values of milk chocolate samples at the peak were 0.50 A.U. and 0.74 A.U., respectively (Figure 5).The absorbance values of the cheap milk chocolate samples at the peak were 0.52 A.U. and 0.79 A.U., respectively (Figure 6). The absorbance values of the white chocolate sample at the peak were 0.52 A.U. and 0.79 A.U., respectively (Figure 7). The absorbance values of the dark chocolate sample with a cocoa content of 78% at the peak were 0.53 A.U. and 0.68 A.U., respectively (Figure 8). The absorbance values of the black chocolate sample with a cocoa content of 92% at the peak were 0.52 A.U. and 0.62 A.U., respectively (Figure 9). The spectra of five types of chocolate can indicate differences in peak intensity (Figure 10).
In1209.81 nmThe absorbance from high to low is as follows: dark chocolate sample with a cocoa content of 78%, dark chocolate sample with a cocoa content of 92%, white chocolate sample, and cheap milk chocolate sample. In1437.32 nmThe absorbance from high to low is as follows: white chocolate, cheap milk chocolate, milk chocolate, dark chocolate sample with a cocoa content of 78%, and dark chocolate sample with a cocoa content of 92%. It can be assumed that this peak represents sugar content.
ConclusionOn average, each chocolate sample weighs 28g. White chocolate contains 15g of sugar, cheap milk chocolate contains 16g of sugar, milk chocolate contains 12g of sugar, dark chocolate with a cocoa content of 78% contains 5g of sugar, and dark chocolate with a cocoa content of 92% contains 2g of sugar. This only suggests a hypothesis that similar trends in milk solids and other seasonings can be derived from other ingredients.
Afterword of the experiment
In summary, this experiment observed differences between different types of chocolate through the use of near-infrared spectroscopy. However, further quantitative analysis must be used to fully explain and quantify the differences in these measurements.
AvaSpec-NIR256-1.7-EVOocean opticsIt is a highly versatile near-infrared spectrometer that can be customized to meet your needs.
AvaSphere-50-LS-HAL-12VBuilt in halogen lamp integrating ballIt is specifically designed for reflectivity measurement, but can also be used in any application where signal strength may be limited, such as near-infrared spectroscopy measurement.
