Instrumental measuring of the hardness of fresh and cooked parsnip (Pastinaca sativa)

The objective of this study was to investigate the application of different instrumental methods for measuring the hardness of fresh and cooked parsnip. Research was carried out on two previously prepared commercial parsnip samples, both fresh and cooked for 5, 10, 15 and 20 minutes. Hardness was measured using a TA. XTPlus Texture Analyzer, equipped with different fixtures and load cells. Penetration test was performed on the parsnip discs, while the instrument was equipped with a 5 kg load cell and a 2 mm diameter stainless steel flat cylinder probe. Shearing test was conducted on the whole parsnip roots with a 30 kg load cell and Warner-Bratzler (WB) flat knife blade. The obtained values of the coefficients of variation for both methods indicated that these methods are more suitable for measuring the hardness of fresh parsnip. The results of analysis of variance showed that penetration test generally expressed better differentiation between the samples A and B. The greatest change of firmness during cooking was observed after the first 5 minutes, as measured by both methods. Parsnip firmness progressively decreased with increasing cooking time, with less pronounced differences between the cooking times obtained by shearing test. Further experiments should include more representative parsnip samples and more repetitions within the sample in order to make general conclusions. All results should be verified with sensory evaluation of parsnip hardness by an expert panel or a panel of trained assessors.