Shellfish Quality Assessment PDF

Shellfish Quality Assessment The following slides were originally developed for Seafish to use in a formal training course on shellfish quality assessment. The following slides are provided for information only with no guarantees (implied or not) or other assuran...

Shellfish Quality Assessment The following slides were originally developed for Seafish to use in a formal training course on shellfish quality assessment. The following slides are provided for information only with no guarantees (implied or not) or other assurances by Seafish. The following slides may be used in part or in their entirety to deliver coaching or training without recourse to Seafish. If you require a formally delivered training programme, delivered by a Seafish approved trainer then please contact [email protected]. Shellfish Quality Assessment Linked to the QCF Unit D/503/2926, 'Demonstrate skills in assessment of shellfish quality (Level 2) Course Schedule 0900 Welcome introductions and objectives 0915 Shellfish family ID - Crustaceans & Molluscs - good quality indictors* 0945 Outline the assessment process - scoring schemes and methods of assessment 1015 Causes of shellfish spoilage 1030 The impact of temperature, handling & seasonality on quality 1045 Break 1100 Preparing for quality assessment 1115 Methods of assessment – Crustacean practical 1300 Lunch 1330 Methods of assessment - Mollusc practical 1500 Break 1515 Completing the assessment process – records and managing the process. 1530 Review/ Q&A 1600 Close 0900 Welcome, introductions, and objectives: Introductions: before we start let’s take a moment to introduce ourselves to the group. Objectives: – 1. Shellfish ID, focus on important UK species – 2. How to prepare for shellfish quality assessment – 3. How to assess the quality of types of shellfish – 4. How to complete the assessment process  Quality products, the key to success! Shellfish is a highly valuable but easily perishable commodity; accurately assessing and maintaining quality fundamental to any shellfish business; Shellfish quality can not be improved once lost; Optimum conditions allow us to slow the spoilage process; To understand quality assessment we must first look at how shellfish spoil and the impact of temperature, handling and seasonality on quality. 0915 Introduction to Shellfish World Map and source of the Coldwater important UK shellfish species prawns Crab, scallops, langoustine, Mussels, oysters & cllams Lobster & Squid, octopus & cuttefish Scallops Warm Warm Squid water Squid water prawns prawns Squid Squid Squid Squid Shellfish commonly eaten in the UK Crustaceans: Brown Crab, Lobster (North American and native), cold water prawns, warm water prawns, langoustine (scampi) Molluscs: Bivalves: Mussels, scallops, oysters, clam selection Gastropods: Whelks and winkles Cephalopods: Squid, Octopus and cuttlefish  Overview of good shellfish quality Shellfish Quality Characteristics Crustaceans Shell is clean, intact, bright & glossy. Prawns should not have any blackspots (prawns, crabs, (an enzymic spoilage) on the shell or a “gritty” feel about them. lobster) Firmly attached head and limbs. Moist, firm, white flesh. Odourless to mild pleasant odour. Squid and Bright skin, no staining and intact. octopus Pure white very firm flesh, not slimy. No "gritty” feel about them Almost no smell.  Overview of good shellfish quality Shellfish Quality Characteristics Live shellfish Clean (no sand, mud, barnacles). (mussels & oysters) Intact closed shell, or closes when tapped. No unpleasant odours. Shellfish Scallop flesh white to cream. (scallops, mussels, Mussel flesh white or orange. oysters) Oyster flesh often grey. Firm, plump, moist & elastic flesh. Orange roe, firmly attached. No excess liquid in package. No unpleasant odours.  Overview of good shellfish quality Shellfish Quality Characteristics Frozen shellfish Hard frozen. Package intact. No ice build up (indicates thawing and refreezing). Individually plastic wrapped or layer packed with plastic sheets. Bright and glossy colour, no gaping of tissues. Clean fresh frozen smell. Shellfish ID slides Depending upon the facilities and samples available the following links can be used to assist shellfish ID during the course of or left out if not required. Crustaceans - http://seafoodacademy.org/Shellfish- Crustaceans.php#Topic46 Bivalves - http://seafoodacademy.org/Shellfish- Molluscs.php#Topic48 Cephalopods – Squid - http://seafoodacademy.org/Squid.php – Cuttlefish - http://seafoodacademy.org/Cuttlefish.php – Octopus - http://seafoodacademy.org/Octopus.php Crustaceans: Brown Crab. Crustaceans: Lobster Crustacean: warm water prawns Crustaceans: Cold water prawns Crustaceans: Nephrops/ Langoustine/ Scampi Molluscs: Bivalves - Mussels Molluscs: Bivalves - Scallops Molluscs: Bivalves Oysters Molluscs: Bivalves - Clam selection  Bivalve Quality Indicators Check Higher Lesser Quality Comment Quality Shell Clean, Chipped or dirty Mussels have byssal threads (filaments) that are intact used to attach the mussel to a surface. These may be present but do not affect the eating quality. In live animals, gaping shells suggest that the animal is dead or dying and should be discarded (it may have been in this condition for some time and could be contaminated). Liquid Clear Slightly (liquor) opalescent (oysters), or slightly milky in colour Flesh Juicy, moist, Starting to Oysters are often turned over when shucked to Texture plump and shrink and look give a "plump" look. firm flat  Bivalve Quality Indicators Check Higher Lesser Quality Comment Quality Colour Mussels Mussels fade; Living environment and feed can influence are either oysters darken flesh colour. white or (but may be a Mussels range from cream to pale or deep orange; brilliant white orange with a black rim. Female mussels are oysters or greenish) orange in colour; males are whitish. vary To determine if an oyster shell is original or naturally re-used, check for a muscle remnant. In a from "freshly" opened oyster, presented on a half greenish shell, the muscle that attaches the flesh to grey to the shell will have been cut, and the flesh white or turned over. When the shell is re-used, it is ivory cleaned and the muscle remnant removed. Note re-using shells can be a health risk, and may be in contravention of food laws. Molluscs: Gastropods Whelks and Winkles. Molluscs: Cephalopods - Squid  Molluscs: Cephalopods - Octopus Picture of octopus good quality required Molluscs: Cephalopods - Cuttlefish 0945 Quality Assessment methods Methods of quality assessment measure different attributes giving a score. Methods can rely on: Microbiological tests; Chemical tests; Electrochemical assessment; Sensory Assessment. Microbiological Quality Assessment Measures the amount of bacteria present, however the process is time consuming, can take 24-48 (or longer) hours to get a result; Number of bacteria not always a good indicator of quality varies with handling and catch area; Useful in ready to eat sector (for food safety) and with bivalve molluscs such as oysters that are often eaten raw.  Chemical Analysis assessment Looks for chemicals that are produced as the shellfish spoil, these include: TMA (Tri-methylamine); TVB (total volatile bases) or TVN (total volatile nitrogen); Hypoxanthine; ATP/ADP/AMP ratios; Peroxide value – measure of fat oxidation. This form of assessment is expensive, time consuming and not that useful for high quality, better at indicating poor quality. Electrochemical assessment Chemical changes in fish flesh can be measured electronically; Equipment is expensive but gives a very quick result; Difficult to use with previously frozen product unless re- calibrated for this type of product. Sensory Assessment Using our senses to judge the appearance, taste, smell and feel of shellfish to determine its quality. Hedonic scoring (personal like or dislike) of limited use (consumer taste panels). An objective approach is better because: Quick; consistent, use human senses to detect the sequence of changes during spoilage. Unfortunately most research and development has been for fish quality. Examples include: Torry Schemes & Quality Index Method (QIM) Senses used in quality assessment Sense used Aspect of Quality determined Sight General appearance and condition, size, shape, physical blemishes, colour, gloss, identity. Smell Freshness, off-odours, taint, oiliness, rancidity, smokiness Taste Freshness, off-flavours, taints, oiliness, rancidity, smokiness, astringency, the primary tastes of acidity, bitterness, saltiness, sweetness. Touch (using fingers and mouth) General texture, hardness, softness, elasticity, brittleness, roughness, smoothness, grittiness, wetness, dryness, crispness, presence of bones. Sensory Assessment – Torry Schemes & Quality Index Method QIM Torry schemes Available for raw and cooked pink and brown shrimps, cooked squid, raw and cooked langoustine tail and cooked scallops. Schemes up to mid 1990s when the Torry Research Lab was closed down. Uses physical indicators to assess quality such as appearance, odour, flavour, texture, mouth feel; Scores for indicators are averaged giving a score linked to freshness (higher the better) Advantages: widely used, effective (QC and scientific trials); gives detailed evaluation of quality, schemes available for raw and cooked. Disadvantages: requires training, limited shellfish species covered, no new schemes coming through. Sensory Assessment – Torry Schemes & Quality Index Method QIM Quality Index Method Schemes are available for Octopus and cuttlefish Developed in the 1990s modifying an Australian scheme. Uses similar indicators as Torry but lower scores are the freshest and each indicator is added to get a total score. Examples of scoring schemes and further information can be seen: See resources page http://seafoodacademy.org/shellfish_quality_assessment.htm  1015 Causes of shellfish spoilage Bacteria; enzymes, oxygen, dehydration. Bacteria Bacteria present and those that come in contact with soft tissue after death will: Lead to bad taste and smell Decompose the flesh, changing how it looks Spoilage bacteria does not cause food poisoning, unlike pathogenic bacteria from careless handling or contaminated water supplies. Growth of bacteria is typically controlled by temperature less than 4 degrees, (live shellfish have optimum shelf life if stored 4-8 degrees) Causes of shellfish spoilage Enzymes Enzymes are biological catalysts - catalysts are substances that increase the rate of chemical reactions without being used up; Are vital to the shellfish’s well being when alive but then start to break down the cells they are found in after death; Are mainly found in the gut of shellfish, after death these then penetrate the flesh Enzymes produce a chemical spoilage that can even continue (slowly) in frozen products, particularly product with freezer burn that has experienced fluctuating temperatures. Causes of shellfish spoilage Dehydration The drying out of shellfish flesh leads to a reduction of flavour, juices and loss of weight, Severe dehydration of frozen product is often referred to as freezer burn. It may result in a dry ‘woody’ appearance or the build up of icicles within pre- packaged goods Dehydration can be minimised by reducing the time of processing and storage. Also using correct packaging such as a plastic film barrier and glazing, of frozen product that is kept at a constant temperature of frozen product below -30°C. Causes of shellfish spoilage Oxygen Particularly a problem associated with long term cold storage as fats can be changed by oxidisation producing a rancid bad smell and taste. The effect of oxidisation takes a period of time and is not normally an issue for chilled short life products The effect of oxygen will depend upon the level of fat in the product which will vary throughout the year depending upon feeding and breeding seasons when harvested. Oxygen is normally excluded by vacuum packing. 1030 The impact of temperature, handling & seasonality on quality Temperature - direct link to bacterial growth & action of enzymes, minimised at temperatures less than 4 degrees. The most significant cause of quality loss. The nature of shellfish flesh is soft and easy to damage, rough handling throughout the supply chain can easily loose quality. Product quality will vary due to seasonal variations in food availability, breeding seasons, crustacea moulting and farm environmental conditions (e.g. algal blooms on a mussel farm). Handling and storage of live crustaceans: Handling and storage of raw crustaceans Spot the product shown here at most risk…. Handling and storage of cooked crustaceans Chilled: should be quickly cooled and stored ideally 0-1 degrees and less than 4 degrees to minimise bacterial growth. Cooked crustaceans are then often hand processed requiring skill and high standards of food safety. Frozen: should be blast frozen (quickly) to maintain quality, products such as cold water prawns are cooked quickly after capture then frozen on board high tech ocean going factory ships Handling and storage of live molluscs Best stored in damp condition 4-8 degrees; in breathable packaging handled carefully; Oysters stored dish shell down to hold internal fluid as oysters open and close. Handling and storage of raw molluscs Stored raw molluscs are usually cephalopods (bivalves must be sold alive if raw & gastropods need to be cooked to be extracted from their shell). Squid, octopus and cuttlefish are sold whole and raw in ice at landing ports and wholesale markets. Cephalopods are also sold widely frozen raw from global supplies. Handling and storage of cooked molluscs Cooked molluscs such as mussels are often further processed e.g. into a frozen seafood mix. Cooked whelks are usually sold chilled in vac packs or frozen in the UK wholesale market 1045 Break 1100 Preparing for quality assessment Taste Calibration is a great way to check assessor’s sensitivity to the four key flavours. Individuals also learn to identify where in their mouth these different sensations are detected. This can help when experiencing the more complex flavours from real samples. Good working practises Quality Assessment should be carried out systematically to minimise errors by trained staff. Careful and consistent labelling of samples under hygienic conditions will reduce the risk mistakes and contamination of samples by the assessor or assessment station. In preparing for quality assessment training samples for comparison must be gathered, labelled accurately and carefully. These are then stored under ideal conditions often in ice, requiring re-icing throughout the storage period. HACCP documentation is used to describe good working practices within any food business. They identify points critical to the food safety of the product during the process and require monitoring of these regularly to document due diligence in food production. Food safety and traceability Live bivalve molluscs must be harvested from appropriately graded waters from around the UK; most require depuration and a health mark to ensure food safety and allow traceability. A retailer must retain all health marks for 60 days Water Classifications. Following regular testing of harvest and areas of aquaculture: 1: Classification A (Cleanest waters can be gathered for direct consumption) 2: Classification B (require treatment in a purification centre, relaying or heat treatment) 3: Classification C (require relaying of at least 2 months, followed by purification or heat treatment).  Bivalve Molluscs: Harvest to sale Local Authority – raises a ‘Movement document’ Gathered from harvesting area to purification/ despatch centre; Health mark produced with name (scientific), origin, date of despatch, centre number, batch number. Retail outlet – incoming supplies record, keep health mark for 60 days. How can we tell shellfish is safe to eat Bivalve molluscs: Health marks are a legal requirements following live bivalves from depuration to retail sale. Handling of shellfish samples What should be considered during the assessment process? Handling should be: Hygienic; Careful & Accurate  How to prepare & handle samples Samples must be: Representative Securely stored Labelled accurately Recorded accurately Limitations of assessment methods The main limitation of shellfish sensory assessment methods is that there are few documented sensory assessment schemes available; Microbiological assessment - Number of bacteria not always a good indicator of quality varies with handling and catch area; Chemical assessment - This form of assessment is expensive, time consuming and not that useful for high quality, better at indicating poor quality. Electro-chemical assessment – The equipment is expensive and difficult to use with previously frozen product unless re- calibrated for this type of product 1115 Methods of assessment – Crustacean practical Assess the quality of raw crustacean shellfish based on appearance, texture and odour; Assess the quality of cooked crustacean shellfish based on appearance, odour, flavour and texture. Crustacean practical Limited schemes available, these are: Torry Assessment Pink & brown shrimp, cooked and raw (difficult to obtain fresh) Torry Assessment Raw and cooked langoustine tails Use of BIM Brown crab – Quality and Handling document Raw Torry shrimp scoresheet – Pink & Brown S Flesh colour & Head Brown shrimp body Connective tissue Head Pink shrimp body Odours opacity 5 translucent Light brown/grey Pale grey, darker grey Grey Brown/dark Orange/pink (eggs Fresh seaweed; through transparent spots red turquoise) delicate; watery casing 4 Slight opacity Slight greening or Grey/slight mauve Duller grey Darkening Slight green/yellow Seaweed; sweet; towards yellowing tinge. Pale yellow tinge laterally. Pale milky; fresh cut grass; anterior ventrally yellow ventrally metallic; iodine (eggs: dirty ferrous green) 3 Opacity Blackening Dark green/ Tangy / sherbet extended half purple lemon; "sharp"; way along flesh musty-mouldy leaves; from anterior hay end which is beginning to turn yellow 2 May still show Grey/green/yellow Green/ Compost; silage; translucency at yellow rotting vegetables; tips of tail. humus; muddy; ditch- Anterior: water; NH3 yellow/green 1 All opaque Covered in large Covered in large Yellowing Green/ Dirty yellow / Urinal; doggy; green/black green/black blotches. black brown/orange. amines; byres; blotches. Blackening Blackening of head Covered in pale sweaty; NH3 of head extending extending along the yellow slime along the body body Torry Assessment of raw and cooked Nephrops (langoustine) tails Assessment 1: Raw samples (link to days on ice?) Score Appearance Odour 5 Shells bright, clean, rosy pink. Telson and Shellfish, marine, seaweed swimmerets clean. Flesh on ventral side clean, white and translucent. 4 Loss of brightness of shell with some dulling. Slight shellfish, slight Loss of translucence of flesh on ventral side. marine, very slight No blackening of shell apparent. ammonia 3 Some darkening of shell along the joint Slight ammonia, loss of between the segments. Shells appear dull. characteristic shellfish Some slight discoloration on the telson. odour Swimmerets showing some darkening. 2 Darkening of the shell more apparent. Dark Moderate ammonia, sour lines between the segments extend and join and off together. Dark spots on telson. Swimmerets show intensive darkening and black spots. 1 Generalised blackening of the shell with Strong ammonia, strong, discoloration from the segment joints sour and off, stale spreading to the complete shell. 0 Shells completely black. Very strong ammonia, putrid Torry Assessment of raw and cooked Nephrops (langoustine) tails Assessment 1: Cooked samples Score Odour Flavour Texture, mouthfeel & appearance 5 Milky-sweet, seaweed. Intensely sweet, Very firm, crisp Slightly sulphurous, metallic characteristic shellfish 4 Milky, creamy, slight Very sweet, creamy, Firm ammonia milky 3 Slight ammonia, loss of Sweet Slightly soft milkiness 2 Ammonia Loss of sweetness, Soft neutral 1 Strong ammonia Sour, off, creamy sour Very soft 0 Strong ammonia, sour Strong off-flavour, Sloppy, little texture bitter, very sour Torry Assessment of Pink & brown shrimp, Nephrops, raw and cooked practical Use samples: As fresh possible 0-3 days; 3-6 days, 6-9 days Brown crab assessment (taken from BIM Handling & Quality Guide) Expected meat High Low yield Topside Shell darkly coloured Shell lightly coloured throughout. throughout. Pie-crust edge is Pie-crust edge is light in colour dark in colour. with pale indentations. Underside Abdomen or flap darkly Abdomen or flap lightly coloured. coloured Shell white or cream in colour with Shell pale yellow to light brown no visible hairs. in colour with visible hairs. Shell soft when the underside of Shell hard when the underside the shell is pressed. of the shell is pressed. Claws Claws dark brown in colour Claws light brown in colour with with cream underside. off-white underside. Brown crab practical: dressing Illustrate yields and flesh quality of male/ female & good and bad quality if practical demo not possible can use YouTube resources and buy in cooked white and brown flesh. 1300 Lunch – Dressed crab! 1330 Methods of assessment - Mollusc practical Assess the quality of cephalopods based on colour, adherence, texture and odour Assess the quality of live bivalve molluscs and gastropods based on the percussion test Assess the quality of molluscs meats based on odour and flavour. Squid quality assessment : Appearance Check Higher Lesser Comment quality Quality Flesh White, Darkens When "freshly" caught, squid have an colour slightly to a attractive translucent flesh. If you put your translucent strong fingers inside the tube, you should be able to when raw pink see them clearly. After death, chemicals are tinge released that discolour the flesh. This process can be aggravated by damage to the internal organs through rough handling. Discolouration is clearly visible when the skin is removed.  Squid quality assessment – skin condition Check Higher Quality Lesser Quality Comments Skin Intact, with Some tears in the If trawled, the skin may have condition distinct skin, some been rubbed off or torn; this patches of broken arms does not necessarily indicate iridescence in poor-quality flesh. squid and Ink on a squid or cuttlefish does cuttlefish not mean poor eating quality, but is a warning of poor handling. It can encourage bacterial growth and should be washed off immediately. Squid quality assessment - Flesh Check Higher Lesser Comments Quality Quality Flesh Elastic, Loss of Squid and cuttlefish are often very firm, elasticity, perceived as being overly tough. not slimy soft, The flesh is naturally firm but can slimy or be toughened by incorrect cooking gritty or overcooking. Grittiness can be caused by foreign matter such as sand. Octopus is naturally firmer than squid and cuttlefish. Mussel quality Rope grown farmed mussels are cleaner and have thinner shells compared to the thicker shelled wild dredged mussel which often have barnacles on the outside; Rope grown are available most of the year (will spawn in the summer). Dredged wild mussel can be cheaper but require cleaning; Mussels have excellent sustainability credentials, but require health marks for food safety Mussels attach to their growing areas with a beard or sticky thread that should be removed just before cooking as removal will weaken the mussel  Percussion test for bivalves and gastropods The percussion test is a simple test for life of uncooked bivalves and gastropods. Bivalves should be tightly closed and gastropods have their operculum (trap door) tightly closed. When weakened the bivalves shells open (as shown) and the gastropods operculum opens. By tapping the shells on a work surface the live shellfish will close again, meaning they are still alive and safe for cooking. Shellfish that do not respond should be discarded. Dry king scallop sold in 2 Kg tubs Cooked mollusc meat assessed for quality on odour & flavour - scallops Score Cooked Odour Cooked Flavour Cooked Texture 5 Sweet milky; Intensely sweet, cloying Chewy; fibrous; rubbery condensed milk 4 Slight milky Less sweet; milky Chewy; fibrous; rubbery sweet; seaweed 3 Neutral; musty Neutral; slightly musty; some Slightly chewy; slightly soft. residual sweetness 2 Slightly sour Sour; bitter; off; some sweetness Slightly chewy; slightly soft/ Soft may still be detectable gelatinous; sticky 1 Sour; sweaty; Sour; bitter; off; some sweetness Soft; gelatinous; sticky. ammoniacal may still be detectable 0 Sulphide; faecal; Very bitter; off; rubber; nauseating stale cabbage Cooked mollusc meat assessed for quality on cooked flavour - squid Score Cooked flavour of squid Days in ice 10 Fresh, characteristic of shellfish, sweet, meaty 0-1 9 slight loss of freshness, creamy, sweet, meaty, metallic 8 slightly sweet, slightly meaty, creamy, milky 6-8 7 no sweetness, caramel 6 neutral 5 Slightly sour 8-10 4 Sour, musty, cabbage 3 Slightly bitter, overripe cheese, oily, slight sulphide 13-14 2 Bitter sulphide 1 Strongly bitter, putrid Mollusc practical samples For each practical assessment collect three sets of samples at: 0-3, 3-6, and 6-9 days. 1500 Break  1515 Completing the quality assessment records Records completed after assessment will include: Supplier of samples Delivery and storage times Product and codes allocated Assessment sheets completed Person completing inspection Identify & address any discrepancies between assessed and anticipated freshness, consider temp. abuse, handling & seasonality, 1530 Review/ Q&A 1600 Close