Distinguishing Grass-fed Beef from Grain-fed Beef Using Near-IR Spectroscopy
This article examines the use of Near-IR spectroscopy to separate grass-fed beef from grain-fed beef. Some cattle graze on pastures, which are lands covered with grass. Other cattle are fed maize, which is essentially corn or other grains. Grass-fed beef has superior nutritional quality compared to grain-fed beef. It is also exceptional in terms of safety and environmental friendliness compared to grain-fed beef¹. Figure 1 depicts the different feeding scenarios for the cattle.
Figure 1: Grass-fed vs Grain-fed feeding methods
Figure 2 shows the difference between the two types of meat.
Figure 2: Difference between Grass-fed and Corn-fed beef
As shown in the figure, grass-fed beef on the right has less pronounced marbling than corn-fed beef. It also has a distinguishable yellow fat due to the presence of vitamin A in the grass. There is also more variety in taste and texture between breeds and origins. The corn-fed beef, on the other hand, is produced by feeding corn or other types of grain to the cattle, antibiotics, and hormones to fatten them. The fat also appears whiter due to a lack of vitamin A. There is also less variety between breeds and origins.
Distinguishing between the two types of meat, especially if done quickly and non-intrusively, is quite helpful for two reasons. First of all, consumers can be aware of the higher quality of meat they are purchasing. Secondly, it stops the fraudulent activities that sell grain-fed beef at a higher price in place of grass-fed beef.
Near-IR spectroscopy is a suitable technique for this kind of investigation, and a number of researchers have already examined the different spectra obtained from grain-fed and grass-fed beef1,5,6. Near-infrared spectroscopy of intact beef (Beef that has not been minced) predicts various quality features, such as fatty acid profiles and pH. Handheld near-IR spectrophotometers are readily available in the market that connect via Bluetooth and save spectra on the smartphone (Android or iOS)1,6.
Figure 3 shows the difference in spectra between grain-fed and grass-fed intact beef samples5.
Figure 3: Difference in spectra between Pasture-fed and Maize silage-fed
There are some distinct differences between the two spectra. First of all, the spectra of animals on maize silage showed four absorption bands at 1732 nm and 1754 nm, related to the CH2 stretch first overtone (different lipid content). At 2310 nm and 2350 nm, respectively, are associated with CH combinationsAt 2310 nm and 2350 nm, respectively, are related to CH combinations. First of all, the spectra of animals on maize silage showed four absorption bands at 1732 nm and 1754 nm, related to the CH2 stretch first overtone (different lipid content), and at 2310 nm and 2350 nm, associated with CH combinations, respectively. First of all, the spectra of animals on maize silage showed four absorption bands at 1732 nm and 1754 nm, related to the CH2 stretch first overtone (different lipid content), and at 2310 nm and 2350 nm, associated with CH combinations, respectively. Secondly, differences at 1638 nm and between 2200 nm and 2300 nm, associated with C-H and C=C groups, suggest that differences in polyunsaturated fatty acids could further contribute to muscle classification (as seeat 1638 nm and between 2200 nm and 2300 nm, related to C-H and C=C groups, suggest that differences in polyunsaturated fatty acids could further contribute to muscle classification (as seen in the absorption spectra). Using NIR spectra, correct classification rates of 80-83% for pasture-fed beef and 79-80% for maize-fed beef were achieved.
The Nirvascan spectrophotometer offered by ASP Laser Inc. has been used in one of these studies1 and successfully classified grain-fed beef and grass-fed beef with a success rate greater than 85%. Both Linear Discriminant Analysis (LDA) and Partial Least Squares Discriminant Analysis (PLS-DA) methods were used for classification.
Figure 4 shows a fiber-optic NIR spectrophotometer (Nirvascan) connected to an external 5 Watt source, which also includes a collecting lens (DRP1) to measure intact beef containing fat.
Figure 4: Fiber optic Nirvascan used with an external Halogen light source to measure intact beef absorption spectrum
Several absorption peaks, including for the CH bond (Fat, 1200 nm peak) and the OH bond (Moisture, Protein, 1450 nm peak), are observed in the measured absorption spectrum.
For more information about the Nirvascan spectrophotometer and its different models, refer to the following link.
https://www.alliedscientificpro.com/nirvascan
References:
- Portable vibrational spectroscopic methods can discriminate between grass-fed and grain-fed beef, C. Coobs et al, JINRS, 2021
- https://www.foodfirefriends.com/grass-fed-vs-grain-fed-beef/
- https://onpasture.com/2017/03/13/whats-the-difference-between-grain-fed-and-grass-fed/
- https://paleorobbie.com/post?id=52
- Visible/near infrared reflectance spectroscopy for predicting composition and tracing system of production of beef muscle, D. Cozzolino et al, Animal Science, 2002
- Handheld near-infrared spectrometer allows online prediction of beef quality traits, A Goi et.al, Meat Science, 184, 2022