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Plaice, Black Sole, Lemon Sole: A Guide to Handling and Quality

28 September 2015

An Bord Iascaigh Mhara

The aim of this guide from the Irish Sea Fisheries Board (BIM) is to provide practical and contemporary guidelines on the handling and quality of plaice, black sole and lemon sole, at all stages, from capture to the first point of sale.

Introduction

Optimal handling and storage practices at sea and ashore are essential elements in the management of fish quality and the achievement of maximum return on national and international markets.

Defining fish quality, however, is not easy. The process includes the understanding and assessment of a range of factors, many of which depend on market preferences such as: species, size, capture method, seasonal condition and freshness.

Freshness, describes the degree of spoilage a fish has undergone since capture and is an important indicator for consumers. Very importantly, and unlike many other quality attributes, this is an area within the management of the catch, over which the fishing industry exerts significant control.

Sensory assessment remains the most popular method of assessing freshness. This type of assessment uses smell, texture and visual appearance to determine the quality of fish. It is a particularly useful technique as it is low cost and requires nothing other than careful and exact training. It is a widespread and reliable assessment method and provides the foundation for the design and application of this guide.

Plaice, black sole and lemon sole are grouped together, in this guide, as they have similar handling requirements.

Pleuronectes platessa

Plaice – English
Leathóg – Irish
Platija – Spanish
Carrelet – French
Solha – Portuguese

Plaice are a diamond-shaped, right-eyed flatfish with a moderately sized head. They are usually a brown or greenish brown colour, with brilliant red or orange spots. The underside is white.

Pleuronectes platessa

Solea solea

Black Sole – English
Sól Dubh – Irish
Lenguado – Spanish
Sole commune – French
Linguado legitimo – Portuguese
Sola – Polish

Black Sole are a right-eyed flatfish, which has a very distinctive shaped head with a rounded snout and a small, down-turned mouth. They are usually a greyish-brown to reddish-brown colour with darker blotches; the pectoral fin has a distinctive black tip.

Solea solea

Microstomus kitt

Lemon Sole – English
Leathóg Mhín – Irish
Mendo limón – Spanish
Limande-sole – French
Solhao limao – Portuguese

Lemon sole are an oval-bodied, right-eyed flatfish with a small head and mouth. They are usually a mottled red-brown, pink and orange colour with flecks of yellow and green. There is a large orange blotch behind the pectoral fin. The underside is white.

Microstomus kitt

Excellent Quality Eyes Gills and Skin Good Quality Eyes Gills and Skin Poor Quality Eyes Gills and Skin Gutting Quality Washing Guide Traditional Boxing and Icing Guide

Hygiene & Cleaning

In addition to correct handling, a high standard of hygiene and cleaning is essential to ensure production of a safe, high quality, seafood product

    • After every haul, the deck, hopper, boxes, gutting area, knives, oilskins, aprons and all other equipment, should be washed down with seawater to remove fish blood, scales, offal, dirt and any other fouling substances.
    • At the end of every trip, the deck, fish hold, hoppers, boxes, gutting area, knives, oilskins, aprons and other equipment, should be washed down using a power hose and detergent to remove fish blood, scales, offal, dirt and any other fouling substances.

Washed down equipment using a power hose

    • A chlorine-based bleach should be used to thoroughly clean working areas and equipment, and inhibit any bacterial growth. To show the importance of this, sample swabs were taken from a hold of a boat where no bleach was used and from a hold of a boat where bleach was used. Under laboratory conditions bacterial growth was greater on the sample swab from the deck where no bleach was used. All residual bleach should be rinsed away with clean seawater.

Bacterial Growth with and without bleach

  • Detergents and sanitizing agents should be from the approved list issued by the Sea-Fisheries Protection Authority (SFPA) and should be used to the product specifications.

By-Product Utilisation

With growing interest in health products, coupled with the need to extract the maximum value from limited seafood resources, the importance of seafood by-product utilisation is growing.

Currently by-products (liver, guts, bones) from commercial fish species are simply discarded at sea, disposed of onshore or reduced to lower value fishmeal.

Ireland has recently focussed research attention in this area, which will lead to an increased demand for raw material from our seafood industry in the future.

The following are some of the valuable byproducts that have been extracted from seafood:

  • Phosphorus and calcium from fish bones has anti-inflammatory properties.
  • Omega-3 oils from fish livers and skeletal frames can be cleaned and used for the production of fish oil capsules.
  • Bioactive peptides isolated from fish are known to have powerful antioxidant properties, which can boost the immune system.
  • Fish is a rich source of vitamins A, E, C and selenium, which can protect the body from the build-up of free radicals.
  • Fish skin and bone are a valuable source of collagen and gelatine.

September 2015

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