A simplified hand-held optical device to estimate the freshness level of fresh-cut corn salad

Scientists at the University of Milan (Italy) have evaluated the feasibility of a simplified hand-held and low-cost optical device to estimate the freshness level of fresh-cut corn salad (Valerianella locusta L.). The main objective of this study was selecting the most significant wavelengths of vis/NIR spectra able to discriminate the freshness levels of fresh-cut corn salad during shelf-life.

The shelf-life of corn salad was monitored both by using a portable commercial vis/NIR spectrophotometer and by performing the standard analyses of pH, moisture and total phenols content. Corn salad samples were stored at 4 and 10 °C for 16 days and at 20°C for 7 days.

Based on acquired spectra with the optical device and through the PLS regression technique, regression models able to estimate the value of tested variables were created.

The scientists have selected 4 wavelengths (520 nm, 680 nm, 710 nm and 720 nm), computed regression coefficients of each quality parameters, and elaborated a multiple linear equation for each parameter, where the wavelengths were the independent variables (x) and the quality parameters (pH, moisture and total phenols content) were the dependent variables (y).

Above: particular of spectral acquisition on corn salad leaf with JAZ vis/NIR system. Side: functional scheme of a simple, hand-held optical device implementing signal intensity measurements at the selected wavelengths and equation to estimate moisture content (MC), pH and total phenols (TP) for supporting decision on corn salad leaf freshness level.

The optical device consists of five components:

a vis/NIR halogen lamp,
a fibre optic probe for reflection measurement,
a spectrophotometer,
hardware for data acquisition and instrument control,
battery as power supply.

The optical device presented is easy to use because it does not need chemometric analyses or a trained personnel, furthermore it can support the standard analyses for shelf-life evaluation of fresh-cut leafy vegetables and provide useful information to improve the management of distribution chain directly to retail store.

Fonte: Beghi R., Giovenzana V., Civelli R., Malegori C., Buratti S., Guidetti R., ‘Setting-up of a simplified hand-held optical device for decay detection in fresh-cut Valerianella locusta L.’, 2014, Journal of Food Engineering, Vol. 127, page. 10-15. Per maggiori info: http://www.sciencedirect.com/science/article/pii/S0260877413005955