Comparison of TOF and SL techniques for in-line measurement of food item volume using animal and vegetable tissues

A comparison between the techniques Time of flight (TOF) and Structured Light (SL), for in-line process, was carried out to determine the volume of several food types with different compositions, structures and dimensions; 2 meat tissue (lean meat and pork fat) and 3 vegetable tissue (potato, apple and avocado). The volume obtained was compared with that determined by physical measurements, employing two statistical methods (a Bland-Altman study and partial least square analysis). Results showed that Structured Light (SL) was a better technique than Time of flight (TOF) for determining volume. The TOF technique was affected by factors which were more influential when the S/V ratio (surface of the sample exposed to the camera and sample volume) increased. SL was slightly affected by the composition of the sample. Fat content and the level of unsaturated fatty acids could be the reason for the reflection of the laser light on the surface of the samples thereby reducing the accuracy. Even so, the values of R2 and RMSE of cross-validation, for the worst fit, demonstrated the quality of the SL technique.

► Times of flight, structured light methods were compared with physical measurements. ► Different commodities were analysed: 2 meat tissue and 3 vegetal tissues. ► Different statistical methods (Bland-Altman and Partial Least Square) were used. ► TOF was affected by factors when the surface/volume ratio increased. ► SL was shown to be a better technique for in-line applications.