Lobster quality indicators for grading

Abstract

Male lobsters (Homarus americanus) harvested as ‘quarters’ (1.25 lbs/567 g) in two time periods (winter, N = 16, and summer, N = 25) of 2018 are examined. Indicators of quality data were collected for each lobster, including non-invasive measures (shell hardness, carapace length, sex, live weight, colour, body shape, location, time of harvest) and invasive measures (blood protein [BRIX] level at time of harvest, cooked weight, meat content). Lobster BRIX levels are used as a proxy for actual meat content and as the key indicator of lobster quality. A regression model of the relationship between the natural logarithmic transformation of lobster BRIX levels (independent variable) and meat content yield as a percentage of shell-on (uncooked) weight (dependent variable) is presented. The objective of this study is to evaluate alternative BRIX-based decision rules for achieving desired meat content percentage yields for preparing shipments to global markets. The present study found that BRIX-based grading rules can be determined to achieve minimum desired meat yields, minimum overall shipment yields and minimum proportions of shipments below desirable yield rate. For a minimum desired industry threshold of 24% meat content, the preferred BRIX value rules are (i) 8.5 mg mL⁻¹ and (ii) ‘9 mg mL⁻¹ with 10% plus condition’. These rules improve the admissibility of samples and reduce the risk of below desirable meat yields.