MusselsAlive Report MEAT QUALITY OF ROPE GROWN SCOTTISH MUSSELS JANUARY, 2013

Transcription

1 MusselsAlive Report JANUARY, 2013 MEAT QUALITY OF ROPE GROWN SCOTTISH MUSSELS The report describes the work developed at IPMA in order to characterize the meat quality of rope grown mussels from Scotland. ANA MAULVAULT ANTÓNIO MARQUES SÓNIA PEDRO MARIA LEONOR NUNES Acknowledgments: MusselsAlive is a research for SME Associations project and has received funding from the EU Seventh Framework Programme FP7 under grant agreement no

2 INDEX 1. TRANSPORT CONDITIONS Transport box Biometric data Mortalities and broken shells 4 2. PERCEIVED FRESHNESS Sensorial analyses of live and cooked mussels Edible meat content Edible meat coloration 8 3. CHEMICAL COMPOSITION Proximate chemical composition Fatty acids profile Inorganic elements REFERENCES

3 MusselsAlive Report Meat quality of rope grown mussels in Scotland Winter, Spring and Autumn 2011 Winter, Spring and Summer 2012 The work developed at IPMA aimed to characterize the meat quality of rope grown mussels from Scotland in order to evaluate the current status of mussel s quality provided to European consumers throughout the year. Mussels were sent by The Scottish Shellfish Marketing Group and received at IPMA (Lisbon) in four seasons: Winter I (sent on the 1 st of March and received on the 2 nd of March, 2011), Spring I (sent on the 13 th of June and received on the 14 th of June, 2011), Autumn (sent on the 14 th and received on the 15 th of November of 2011), Winter II (sent on the 25 th of January and received on the 26 th of January, 2012), Spring II (sent on the 1 st of May and received on the 2 nd of May, 2012), and Summer (on the 11 th of July and received on the 12 th of July, 2012). Once in Portugal, the mussels were immediately examined and several parameters were checked namely: 1. Transport box and net bags 2. Biometry 3. Mortality 4. Sensorial analyses of raw and cooked mussels performed by a professional panel 5. Edible meat content 6. Meat chemical assessment This report is divided in three main sections. The first section is the Transport Conditions and comprehends the parameters one to three of the above list. The second part describes the results of the sensorial analyses and the edible content and is entitled Perceived Freshness. Finally, the main results of the chemical analyses, including proteins, fat, glycogen, ash, moisture, fatty acids, amino acids and inorganic elements are shown in the third section - Chemical Composition. 2

4 1. TRANSPORT CONDITIONS 1.1 Transport box Mussels were packed in 10 net bags in Spring (I and II) and Winter (I and II) seasons. The samples received in Autumn consisted only in a large net bag containing all mussels. In Summer, 15 net bags with Scottish mussels were sent. Nevertheless, once at the laboratory (in Lisbon, Portugal), the mussels were divided and distributed into 9 different recipients. In all seasons, samples were transported in Styrofoam boxes, containing packed ice to keep low temperature, i.e. around 10 ºC upon arrival to Lisbon, in all cases (Figure 1). Additionally, paper journal was used to maintain moisture in Winter I and Spring I samples. A A B C D E F Figure 1 - The different layers wrapping the net bags containing mussels: A - Winter I (2011); B Spring I (2011); C Autumn (2011); D - Winter II (2012); E Spring II (2012); F Summer (2012). 1 - Packed Ice; 2- Insulating plastic layer; 3 Paper Journal: 4 Net bag with live mussels. 1.2 Biometric data As shown in Table 1, each net bag of Winter I mussels had ± 15.2 g, corresponding to 75 mussels each, whereas in Winter II the net bags weighted in average ± 38.8 g and contained 98 mussels. In Spring I, net bags weighted 960 ± 25.2 g, each having 77 specimens, but in Spring II a higher number of mussels were found per net bags (100 mussels), each weighting ± 29.5 g. The samples received in Autumn consisted only in a large net bag containing all mussels sent from Scotland. Nevertheless, once at the laboratory (in Lisbon, Portugal), the mussels were divided and distributed into 9 different recipients. Each 3

5 recipient contained, in average, 67 mussels and weighted ± 2.6 g. Summer sample consisted of 15 net bags, each weighing ± 14.9 g which corresponded to an average of 86 mussels per net bag. Table 1 Winter (I and II), Spring (I and II), Autumn and Summer mussels biometric parameters. Biometrics Winter I Spring I Autumn Winter II Spring II Summer Net bag weight (g) ± ± ± ± ± ± 14.9 Mussels/net bag 75.0 ± ± ± ± ± ± 2.8 Mussel weight (g) 18.9 ± ± ± ± ± ± 3.3 Mussel length (mm) 68.3 ± ± ± ± ± ± 6.1 Mussel width (mm) 24.1 ± ± ± ± ± ± 2.3 In general, mussels harvested in Winter II, Spring II and Summer presented lower lengths and weights, whereas larger specimens were collected in Winter I, Autumn and Spring I. 1.3 Mortalities and broken shells Each net bag was visually inspected. As shown in Figure 2, mortality percentages during transportation were very high on Winter I and Spring I (18% and 35%, respectively, not including broken shells), since these samples only arrived at Lisbon 4 days after being collected. The mortalities observed in Autumn, Winter II, Spring II and Summer were much lower, never exceeding 10%. When including mussels with broken shells the mortalities were slightly higher, indicating that mussels should be handled and transported carefully along the trade chain to avoid such losses. Despite the results obtained, it is important to note that mussels net bags should not be kept inside a closed plastic bags (as observed in Spring II sampling) since this does not allow animals to breath, causing the decrease of condition index and higher mortality rates during transport. Figure 2 - Mussel s mortality rate and mortality including broken mussels (%) in each net bag after transport from Scotland in a Styrofoam box. 4

6 In general, mortality (excluding broken shells) in each season was variable among bags, with an average of 6 % in Autumn, 2 % in Winter II, 4 % in Spring II and 10% in Summer. 5

7 2. PERCEIVED FRESHNESS 2.1 Sensorial analysis of live and cooked mussels Ten experienced panellists analysed the live mussels shell appearance and smell in Winter I, Spring I, Autumn, Winter II, Spring II and Summer. The panel also scored odour, flavour and texture of steamcooked mussels. At the end, a global rate for each treatment (live and cooked) was attributed to the mussels. In each season, six mussels were analysed per panellist (3 raw and 3 cooked), totalizing thirty live mussels and thirty steam-cooked mussels LIVE MUSSELS SENSORIAL ANALYSES The descriptors used to characterize live mussels are indicated in Table 2. Shell appearance Closed, cleaned Table 2. Scale of sensorial evaluation of live mussels Closed, dirty (algae, mud) Open, cleaned Open, dirty Shell Odour Characteristic sweet fresh Non-specific slightly sweet Neutral Slightly to ammonia Ammonia Very unpleasant Global Rate Very Good Good Acceptable Rejected Fresh live mussels harvested in Winter II, Spring I and Autumn were scored, globally, as very good or good (100 %, 80 % and 70 %, respectively; Figure 3), whereas Spring II and Summer mussels presented the lowest scores. Smell was the most important attribute influencing the global appreciation. Figure 3 - Scores attributed to live mussels harvested in Winter I, Spring I, Autumn, Winter II, Spring II and Summer (shell appearance, smell and global rate). The percentage of answers given by the panellists is evidenced according to the scale classes used (see table 2) represented by the colour coded bars. 6

8 STEAMED COOKED-MUSSELSSENSORIAL ANALYSES Mussels were also steam-cooked at 100 ºC during 3 minutes and served to experienced panellists at room temperature. The scale used to characterize steam-cooked mussels is indicated in Table 3. Odour Taste Table 3. Descriptors for sensory evaluation of steam-cooked mussels (adapted from Pastoriza et al., 2004) Characteristic sweet fresh Characteristic mild Non-specific slightly sweet Characteristic slightly mild Neutral Strong Slightly to ammonia Slightly sour Ammonia Sour Very unpleasant Sickening Texture Very firm Firm Slightly firm Slightly soft Soft Very soft Global Rate Very Good Good Acceptable Rejected Globally, steam-cooked mussels were better scored than raw ones (Figure 4). Despite the better taste and texture presented by Spring II mussels, panellists identified, in general, a less characteristic and/or sweet smell in this sample compared to those collected in the other seasons. For this reason, 40 % of Spring II mussels were rated only as acceptable. An unpleasant smell (10%) along with a sickening taste (20) lead to the lowest global rates attributed to Summer samples (rejected by 30% of the panel). Figure 4 - Score attributed to steam-cooked mussels harvested in Winter I, Spring I, Autumn, Winter II, Spring II and Summer (shell appearance, smell and global rate). The percentage of answers given by the panellists is evidenced according to the scale classes used (see table 2) represented by the colour coded bars. 7

9 2.2 Edible meat content The highest percentage of edible weight was found in mussels harvested in Spring II (56 %), whereas Winter I mussels revealed the lowest percentage (41 %) (Figur 5. Summer mussels from Scotland presented lower meat yields than those harvested in Norway but higher than those obtained in Irish mussels in the same season (56 % and 45 %, respectively). Nevertheless, Scottish mussels (Winter, Spring, Autumn and Summer) meat yields were higher than those reported by Fuentes et al. (2009) in different parts of Spain. A B Figure 5 - A Winter (I and II), Spring (I and II), Autumn and Summer mussel s total weight (shell included); mussel s edible weight; and the proportion of edible weight to the whole animal meat yield (%). Data is presented as average ± Standard Deviation; B Comparison between the meat yield of Summer mussels from Norway (own data), Ireland (own data), and Spain (Fuentes et al., 2009). 2.1 Edible meat coloration The edible meat coloration was evaluated using the three LAB parameters: lightness (L*; 0 means black and 100 means white), red/green (a*; negative values means green and positive values indicate red) and yellow/blue (b*; negative values means blue and positive values indicate yellow). The values were converted to the RGB range of values and different tones were obtained in each sampled season, with the help of Adobe Kuler tools (Figure 6). Coloration of Winter and Spring mussel meat samples collected in 2011 (I) and 2012 (II) was similar. Autumn mussels meat presented the lightest tone, whereas in Spring (I and II) samples a darker and more intense tone was observed. 8

10 WINTER SPRING AUTUMN SUMMER I and II I and II Figure 6 - Scottish mussels average edible meat coloration converting LAB values to RGB values ( In general, live and steam-cooked mussels harvested in Summer revealed lower acceptance than those harvested in Winter, Autumn and Spring, mostly due to the unpleasant smell and taste detected. Spring mussels revealed higher meat yield percentages (55.5%) a darker and more intense coloration of meat. 9

11 3. CHEMICAL COMPOSITION 3.1 Proximate chemical composition The proximate chemical composition of Winter (I and II), Spring (I and II), Autumn and Summer mussel samples is shown in Table 4. Regardless of origin and season, mussels reveal high moisture and protein contents. Winter (I and II), Spring I and Summer mussels had a leaner flesh, but higher moisture contents. On the other hand, mussels sampled in Autumn and Spring II had higher fat contents. The chemical composition found in Scottish mussels was similar to those of Norwegian, Irish and Spanish mussels (Musselsalive data; Fuentes et al., 2009). Table 4 - Mussels proximate chemical composition (%). Data is presented as average Comparison between the composition of mussels from Norway (own data), Ireland (own data) and Spain (data from Fuentes et al. (2009). ND - No data. Ebro Scotland Norway Ireland Galicia Valencia Parameters Delta Winter I Spring I Autumn Winter II Spring II Summer Summer Summer Summer Summer Summer Moisture Proteins Ash Carbohydrates ND ND ND Fat Fatty acids profile The fatty acid profiles of Scottish mussels harvested in Winter (I and II), Spring (I and II), Autumn and Summer are shown in Figure 7. Summer mussels revealed the highest content of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) with 47.2% and 25.1%, respectively, whereas the highest percentages of polyunsaturated fatty acids (PUFA) were observed in mussels harvested during Winter I and Spring I (52.8% and 51.5%, respectively). Total concentration of omega-3 PUFA was also higher in Spring I (45.5%), while the highest percentage of omega-6 PUFA was found in Winter I samples (6.8%). However, the best ratio of n-3/n-6 was obtained in Spring II samples (14.2) and lower in Winter I (6.6). 10

12 Figure 7 Fatty acids profiles of Winter (I and II), Spring (I and II), Autumn and Summer mussels harvested in Scotland. In the SFA group (Figure 8), palmitic acid (16:0) was the predominant fatty acid in all samples, reaching the highest value in Summer (26.1%) and the lowest in Winter I. Palmitic acid has been reported in numerous studies as the major SFA in mussels (e.g. Alkanani et al., 2007). Figure 8 Saturated fatty acids of Winter (I and II), Spring (I and II), Autumn and Summer mussels harvested in Scotland. Regarding MUFA, palmitoleic acid (16:1n-7+n-9) was the most abundant fatty acid (Figure 9), with the highest content in Spring II mussels (16.9%) and the lowest in Winter I (7.1%). 11

13 Figure 9 Monounsaturated fatty acids of Winter (I and II), Spring (I and II), Autumn and Summer mussels harvested in Scotland. Eicosapentaenoic (EPA; 20:5n-3) and docosahexaenoic (DHA; 22:6n-3) acids were the most important PUFA in all samples (Figure 10). Higher levels of EPA were found during Spring (I and II, respectively, 23.2% and 26.6%), whereas the lowest values were observed in Summer (10.5%). Concerning DHA, the percentages were lower than those of EPA, varying between 4.1% (Summer) and 10.0% (Winter I). Figure 10 Polyunsaturated fatty acids of Winter (I and II), Spring (I and II), Autumn and Summer mussels harvested in Scotland. 3.3 Inorganic elements ESSENTIAL ELEMENTS Almost all elements considered as essentials, i.e. those provided through the diet and required to maintain normal physiological functions can be found in Scottish mussels. Figure 11 shows the elemental composition of Winter (I and II), Spring (I and II), and Autumn mussels. 12

14 Figure 11 Macro and trace elements concentration in Scottish mussels harvested in Winter (I and II), Spring (I and II), Autumn and Summer. Globally, higher concentrations of Cl, Zn and Sr were found in mussels harvested in Winter II, whereas Summer mussels presented higher contents of Ca and Br. Autumn samples revealed the highest contents 13

15 of K, S and Cu. Fe was higher in Winter I samples, whereas Spring II showed higher Rb levels. The concentration of Se did not greatly vary among seasons. Considering this dichotomy, risk assessment of essential elements has to take into account the two ends of the toxicity spectrum: those associated with intakes that are too high (toxicity), and those associated with intakes that are too low (nutritional deficiencies). The USA Food and Nutrition Board of the Institute of Medicine (IOM) has dealt with nutritional deficiency problems, as well as with their toxicity, by setting dietary reference intakes (DRI), which includes the recommended dietary allowance (RDA), adequate intake (AI) and tolerable upper intake level (UL) for essential elements. Table 5 shows the RDA/AI and UL of some essential elements, together with a small description of their functions and adverse effects if consumed in excess. Table 5 - Dietary reference intakes for essential elements (mg/day) from food and water (adapted from Barrento, 2010). Element Function RDA/AI UL Adverse effects of excessive consumption Potassium K Sodium Na Calcium Ca Iron Fe Required for normal cellular function 4700* ND Hyperkalemia Required to maintain extracellular volume and plamsa osmolality Blood clotting, muscle contraction, nerve transmission, bone and tooth formation Prevents anemia 1500* 2300 Elevated blood pressure, increased risk factor for CVD and renal diseases 1000* 2500 Kidney stones, hypercalcemia, milk alkali syndrome and renal insufficiency 18 ( ) 8 ( ) 45 Gastrointestinal distress Copper Cu Zinc Zn Selenium Se Magnesium Mg Manganese Mn Component of enzymes in iron metabolism Component of multiple enzymes and proteins, involved in the regulation of gene expression Protection against oxidative stress, regulation of thyroid hormone action, reduction and oxidation of vitamin C and other molecules Cofactor of enzyme systems Involved in the formation of bone, as well as in enzymes from amino acid, cholesterol and carbohydrate metabolism Gastrointestinal distress, liver damage 8 ( ) 11 ( ) 40 Reduced Cu levels Hair and nails brittleness and loss 320 ( ) 420 ( ) 1.8* ( ) 2.3* ( ) ND No evidence of adverse effects from consumption of naturally occurring Mg in foods; Mg containing supplements may cause osmotic diarrhea 11 Elevated blood concentration and neurotoxicity Abbreviation: (RDA) recommended dietary allowance; (AI) adequate intake; (UL) tolerable upper intake levels. RDA values are in bold type while AI are in ordinary type followed by an asterisk (*). All reference intakes shown are for adult males ( ) and females ( ) aged 19 to 50 years. (ND) not determinable due to lack of data of adverse effects in this age group and concern with regard to lack of ability to handle excess amounts. Source of intake should be from food only to prevent high levels of intake (IOM, 1997; 2001; 2004); ( ) female and male adults aged between 31 and 50 years. 14

16 RDA is set to meet the daily dietary needs of almost all (97 to 98 %) healthy individuals in a particular life stage (e.g. infants, children, pregnancy and lactation) and gender group. The AI is believed to cover the needs of all individuals in a life stage group, but lack of data prevent being able to specify with confidence the percentage of individuals covered by this intake. The UL is the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects to almost all individuals in the general population. Considering that an adult may eat the equivalent to 100 g of mussels edible meat per meal (approximately, 13 mussels), this product is an excellent source of Se and a good source of Zn, Cu and Fe CONTAMINANTS In addition to essential elements, toxic elements, such as Hg, Cd, Pb and As, can also be found in some marine species. Such elements are available in water from natural sources, such as rocks, as a result of human activities like emissions from industrial processes. These elements are taken up by marine organisms through the diet and gills, and tend to accumulate in species occupying higher trophic levels, like fish and shellfish (EFSA, 2004, 2005). Regular consumption of contaminated seafood can cause poisoning and promote diseases. In the European Union, the European Commission has set maximum levels for Cd, Pb and Hg but not yet for As (EC No. 1881/2006; Table 6). To ensure an efficient protection of public health, products containing contaminants exceeding the maximum levels should not be placed on the market either as such, after mixture with other foodstuffs or used as an ingredient in other foods (EC No. 1881/2006). Table 6 - Maximum level (ML, ppm) for Hg, Cd and Pb in bivalves according to the EC regulation No 1881/2006 of 19 December 2006, setting maximum levels for certain contaminants in foodstuffs. Element ML (ppm) Adverse Effects Observations Arsenic As ND No data on the possible adverse effects of organic arsenic compounds in food were found. Inorganic arsenic is a known toxic substance. There is no established maximum level for Arsenic. Cadmium Cd 1.0 Nephrotoxicity, osteoporosis, carcinogenicity and genotoxicity, teratogenicity, and endocrine and reproductive effects. Long biological half-life in mammals. In humans, steadystate concentrations in the renal cortex are reached after about 40 years. Lead Pb 1.5 Neurotoxicity, anaemia, renal toxicity and subsequent carcinogenicity and cardiovascular effects; impairment of the reproductive system. Pb in seafood is inorganic, and is bound to proteins. Bioaccumulation in marine animals is low compared to mercury. Main sites of Pb accumulation in seafood: internal organs, skin and bone, but not in muscle. Mercury Hg 0.5 Neurotoxicity. High exposure in uterus has resulted in cerebral palsy or severe mental retardation in the neonate. Organic Hg is considered to be more toxic than other forms of Hg following ingestion. Methyl-Hg is the predominant form of Hg in fish (> 90 %). 15

17 Despite the, relatively, higher concentrations of Cd and Pb found in Spring I samples (Figure 12), the values are still well below the levels set by the EU (Table 5), thus indicating that mussels harvested in Scotland are safe for consumption all year round. Presently, the EU has not established a maximum level for As, but the concentrations obtained in Scottish mussels have shown to be very low compared to other seafood products (Muñoz et al., 2009), thus not representing any risk to consumers. Figure 12 Contaminants concentration in Scottish mussels harvested in Winter (I and II), Spring (I and II), Autumn and Summer. Overall, Scottish mussels are a lean and safe seafood product, as very low contamination levels were found in Scottish mussels. 16

18 4. REFERENCES Alkanani, T., Parrish, C. C., Thompson, R. J., & Mckenzie, C. H. (2007). Role of fatty acids in cultured mussels, Mytilus edulis, grown in Notre Dame Bay, Newfoundland. Journal of Experimental Marine Biology and Ecology, 348, Barrento, S. (2010). Nutritional quality and physiological responses to transport and storage of live crustaceans traded in Portugal. Instituto de Ciências Biomédicas Abel Salazar da Universidade do Porto (PhD thesis in English). 261p. EFSA (2004). Opinion of the scientific panel on contaminants in the food chain on a request from the Commission related to cadmium as undesirable substance in animal feed (Question N EFSA-Q ). The EFSA Journal, 72, EFSA (2005). Opinion of the scientific panel on contaminants in the food chain on a request from the European Parliament related to the safety assessment of wild and farmed fish. Question N EFSA-Q The EFSA Journal, 236, Fuentes, A., Fernández-Segovia, I., Escriche, I. & Serra, J. A. (2009). Comparison of physico-chemical parameters and composition of mussels (Mytilus galloprovincialis Lmk.) from different Spanish origins. Food Chemistry, 112(2), Muñoz, O., Devesa, V., Suñer, M.A., Vélez, D., Montoro, R., Urieta, I., Macho, M.L., Jalón, M., Arsenic in cooked seafood products: study on the effect of cooking on total and inorganic arsenic contents. Journal of Agricultural and Food Chemistry, 49: Pastoriza, L., Bernárdez, M., Sampedro, G., Cabo, M. L. & Herrera, J. J. R. (2004). Elevated concentrations of oxygen on the stability of live mussel stored refrigerated. European Food Research Technology, 218,