ศูนย์นวัตกรรมเทคโนโลยีหลังการเก็บเกี่ยว

Objective method for measuring firmness of iceberg lettuce.

Schofield, R. A.; DeEll, J. R.; Murr, D. P.;

HortScience Year: 2000 Vol: 35 Issue: 5 Pages: 894-897 Ref: 9 ref.

2000

บทคัดย่อ

Traditional hand compression firmness scores of iceberg lettuce (Lactuca sativa) heads were compared with force-deformation data collected from parallel-plate compression tests conducted with a universal testing machine. Sample deformation was measured over a load range of 30 to 40 N. A quadratic response surface best described the relationship between hand firmness scores (1 to 5 scale) and three measurements of sample deformation (mm). Sample deformation was as precise as hand compression in measuring lettuce firmness, and it provided improved reproducibility by eliminating much of the human error. Although adequate for most firm heads, the predictive ability of the statistical model was weak for soft heads (when the hand firmness score was <2), and for heads with inconsistencies in firmness because of uneven leaf distribution. The minimum sample size required to determine accurately the mean firmness score ( plus or minus 0.5 units) of a population of harvested lettuce was approx equal to 20

heads. This may be a disadvantage, since sampling one head requires approx equal to 1.5 minutes. Overall, the instrument-based method measures lettuce firmness as precisely as the hand compression method, and provides a standardized, objective measurement for postharvest researchers when exchanging or reporting firmness data.