Research Issues in Inactivation of Listeria monocytogenes Associated with New Zealand Greenshell Mussel Meat (Perna canaliculus) Using High-Pressure Processing

ABSTRACT

New Zealand Greenshell mussels are currently shucked by heat processing, and this can be used as a listericidal step. Shucking by high pressure processing (HPP) has potential benefits in product quality and increased yield, but processors need to understand the effects of this technology on the safety of their product with respect to Listeria monocytogenes. L. monocytogenes was mixed with minced mussel meat, and 2 g samples (in foil pouches) were subjected to HPP at various pressures, times, and temperatures. Of 10 tested strains of L. monocytogenes, the most resistant to HPP at 400 MPa (Food Science Australia strain 2655 isolated from Australian processed meat) was selected for subsequent work. This strain showed two-phase inactivation kinetics in response to time at 400 MPa. Approximately 5 log₁₀ cells/g were rapidly inactivated in a log-linear fashion with time while the remaining cells were inactivated at a slower rate. There was also some evidence of a shoulder in the inactivation curves. In the temperature range tested (10°C–40°C), the log-linear inactivation rates showed linear increases with increasing processing temperature at 400 MPa with a z value of 29.1 min.     

Freshwater Pearl Culture Technology Development in India

ABSTRACT

Development of science and technology of cultured pearl production in a freshwater environment in India is described. Distribution of Indian pearl mussels, pond mussel Lamellidens marginalis, paddy field mussel L. corrianus, and riverine mussel Parreysia corrugata in relation to environmental variables such as type of soil, nature of sediment substratum, presence or absence of macrophytes (Eichhornia sp., Nechamandra sp., andNymphaea sp.) is described. Food and feeding of the mussels, together with density aspects in culture conditions are discussed. Mussel breeding including specificity in fish hosts, and mussel larval parasitic relationships are discussed. Basic steps involved in indigenous freshwater pearl culture technology are summarized. Pearl culture grafting procedures such as mantle cavity, mantle tissue and gonadal implantation along with different pearl products are also described.     

Biofouling on Greenshell? mussel (Perna canaliculus) farms: a preliminary assessment and potential implications for sustainable aquaculture practices

Greenshell? mussel (Perna canaliculus) culture is the primary aquaculture industry in New Zealand. However, our knowledge of biofouling on Greenshell? mussel farms, and its contribution to farm ecotrophic effects, is poor. We conducted a preliminary study of biofouling accumulation at two Greenshell? mussel farms during Intermediate and Final seed on-growing stages (each of 6?months duration) with sampling of mussel ropes at 0, 3, 5 and 6?months during each on-growing stage. A diverse range of biofouling organisms (71 distinct taxa) accumulated on mussel ropes, with biofouling biomass dominated by suspension-feeding organisms (~88% of biofouling biomass) such as other bivalves, ascidians and, to a lesser degree, bryozoans. Biofouling biomass increased with culture time, varied between farms and was generally greater at 2?m than at 8?m depth. After 6?months, biofouling organisms on average comprised 54% of the total rope biomass. The reseeding of ropes between Intermediate and Final seed crops reduced the amount of non-Greenshell? mussel biofouling. However, after 6?months, non-Greenshell? mussel biofouling on average still comprised 15% of the total rope biomass. To evaluate potential ecotrophic effects of biofouling on Greenshell? mussel farms, we compare the clearance rates of Greenshell? mussel longlines based on Greenshell? mussels alone and when combined with the two dominant biofouling species observed in our study (the mussel Mytilus galloprovincialis and the ascidian Ciona intestinalis). Our study shows that accumulated biofouling biomass on Greenshell? mussel ropes can be significant and recommends further investigation as to actual ecotrophic effects of biofouling to ensure sustainable mussel farm practices.     

A sensory and nutritional validation of open ocean mussels (Mytilus galloprovincialis Lmk.) cultured in SE Bay of Biscay (Basque Country) compared to their commercial counterparts from Galician Rías (Spain)

Mussel shell biometry, nutritional quality as well as consumer sensory evaluation of experimental open ocean cultured mussel Mytilus galloprovincialis (Lamarck 1819) were analyzed and compared to that of commercial mussels from Galician Rías available in the local market. Both mussel products were of the same commercial size. In this study, open ocean mussels were significantly higher and wider than those of Galician Rías. In addition, with the exception of ash content, both mussel products showed similar biochemical composition. Regarding fatty acid profiles, however, statistical differences were detected. These differences were not fully reflected in the sensory assessment. In terms of consumer acceptability, both mussel products were considered equally satisfactory.

     

Implicit price of mussel characteristics in the auction market

This study explores desired and undesired characteristics of mussels in wholesale market by applying hedonic price analysis. Transaction data in auction market in Yerseke, the Netherlands, was used to estimate linear and semi-log price models. Meat content and size count, which are measured as the ratio of the weight of cooked meat to the total weight and the number of mussel per kg of raw mussels, respectively, are the most important characteristics determining the price. At the sample mean, if the meat content increases by 1%, farmers can get a premium price of 5.5 eurocents kg^?1 of raw mussel. Mussel lots with size counts below 50 pieces kg^?1 can command the highest implicit price of size. Processors prefer mussel lots in which the size of mussels is more or less heterogeneous. The impurity of mussel lots, which is measured by the percentage of tare, the amount of barnacles and limpets per kg of raw mussels are significant discounting factors on the price. The study also investigates the impact of farming locations and seasons on the price and the price trend during the period of 2002–2009.     

Prevalence and Serotype Distribution of Listeria monocytogenes in Salted Anchovy,Raw Anchovy,and Raw Mussel Using IMS-Based Cultivation Technique and PCR

In the present study, a total of 150 samples including 50 salted anchovy, 50 raw anchovy, and 50 raw mussel samples collected from the retailers and small-scale producers in Samsun province from the Black Sea region of Turkey were analyzed; and 12% (6/50), 2% (1/50), and 2% (1/50) of the samples, respectively, were found to be contaminated with L. monocytogenes. According to the serotype distribution, six salted anchovy and one of the raw fish samples were contaminated with L. monocytogenes 1/2b (or 3b). In one raw mussel, both L. monocytogenes 1/2b (or 3b) and 4b (or 4d or 4e) serotypes were detected.     

Incidence,Growth, and Inactivation of Listeria monocytogenes in Cooked and Peeled Cold-Water Shrimp

ABSTRACT

Cooked and peeled cold-water shrimp (Pandalus jordani) naturally contaminated with Listeria monocytogenes were obtained from a processor for a series of studies to determine the level of contamination and growth characteristics of this bacterium in the naturally contaminated product. L. monocytogenes was isolated from every 25-g sample of individually quick frozen (IQF) shrimp that was tested. The level of contamination in each composite sample ranged from 5 to 16 colony forming units (CFU) per 25 g. When individual shrimp taken from the 25-g sample portions were tested separately, samples positive for L. monocytogenes ranged from 1 of 12 to 5 of 15 shrimp tested. The project also evaluated the effectiveness of three methods to inactivate the bacterium: ozone, chlorine dioxide, and steam as possible product reconditioning strategies. Ozone and chlorine dioxide were both found to be ineffective reconditioning treatments for shrimp naturally contaminated with L. monocytogenes. Experiments with steam conducted at the laboratory and later at the shrimp processing plant verified that shrimp contaminated with L. monocytogenes could be safely reconditioned by steam pasteurization. Steam was used successfully to pasteurize several thousand pounds of contaminated shrimp in the processing plant. When the naturally contaminated product was packaged in either oxygen-permeable or impermeable films and stored at 5°C and 10°C, the product was deemed spoiled by sensory evaluation after 9 days of storage, at which time the L. monocytogenes population were 3 × 10⁴ CFU per g. By comparison, when an isolate (strain 4311) from naturally contaminated shrimp was inoculated onto the pasteurized shrimp at a concentration of 12 cells /25g, the L. monocytogenes population reached 3.0 × 10⁸ per g after 9 days of storage. The pasteurization process used in this study would not be effective in inactivation of Clostridium botulinum. Ready-to-eat-shrimp must therefore be stored below 3°C or frozen.     

Color,Yield, and Texture of Heat and High Pressure Processed Mussels During Ice Storage

High pressure processing (HPP) can shuck (open) shellfish, saving labor while conferring food safety and yield benefits. Mostly male New Zealand Greenshell? mussels (Perna canaliculus) were HPP-shucked (3 min at 500 MPa, 30°C) and assessed during 6-days’ ice storage (0°C) for cooked yield, color, and texture compared with heat processed (1 min at 70°C) and untreated samples. HPP-treated mussels had improved yields but lost more weight during ice storage. Male mussels from all treatments became darker with ice storage. HPP-treated mussels had firmer adductor muscles, while their guts required higher maximum force but less energy to puncture them.     

Evaluation of partial replacement of live and fresh feeds with a formulated diet and the influence of weaning <Emphasis Type="Italic">Panulirus ornatus</Emphasis> phyllosomata onto a formulated diet during early ontogeny

We have evaluated the potential of a formulated diet as a replacement for live and fresh feeds for 7-day post-hatch Panulirus ornatus phyllosomata and also investigated the effect of conditioning phyllosomata for 14–21 days on live feeds prior to weaning onto a 100% formulated diet. In the first trial, the highest survival (>55%) was consistently shown by phyllosomata fed a diet consisting of a 50% combination of Artemia nauplii and 50% Greenshell mussel, followed by phyllosomata fed 50% Artemia nauplii and 50% formulated diet and, thirdly, by those receiving 100% Artemia nauplii. The second trial assessed the replacement of on-grown Artemia with proportions of formulated diet and Greenshell mussel that differed from those used in trial 1. Phyllosomata fed a 75% combination of formulated diet and 25% on-grown Artemia and 50% on-grown Artemia and 50% Greenshell mussel consistently showed the highest survival (>75%). Combinations of Greenshell mussel and formulated diet resulted in significantly (P < 0.05) reduced survival. In trial 3, phyllosomata were conditioned for 14, 18 or 21 days on Artemia nauplii prior to weaning onto a 100% formulated diet, which resulted in survival rates that were negatively related to the duration of feeding Artemia nauplii. In the final trial, phyllosomata were conditioned for 14 days on live on-grown Artemia prior to weaning onto one of three formulated diets (one diet with 44% CP and two diets with 50%). Phyllosomata fed a 44% CP diet consistently showed the highest survival (>35%) among all treatments, while those fed a 50%-squid CP diet showed a significant (P < 0.05) increase in mortality at day 24. The results of these trials demonstrate that hatcheries can potentially replace 75% of live on-grown Artemia with a formulated diet 7 days after hatch. The poor performance associated with feeding combinations of Greenshell mussel and formulated diet, and 100% formulated diet as well as conditioning phyllosomata for 14–21 days on live feeds prior to weaning onto a formulated diet highlights the importance of providing Artemia to stimulate feeding.     

The impact of publication on freshwater pearl mussel conservation: To conceal or to reveal the location of threatened habitats?

• 1. The freshwater pearl mussel, Margaritifera margaritifera, is a threatened species. One of the threats faced by this species is direct extermination by poachers, and therefore some researchers conceal information on the locations of pearl mussel habitats. For example, some researchers do not publish the names of the rivers where pearl mussels occur, whereas other researchers do.
• 2. Concealing the names of rivers containing pearl mussels makes them unknown not only to potential offenders but also to administrators, nature conservation practitioners, and ordinary citizens. As a result, no protection measures are undertaken, which is all the more regrettable as damage to pearl mussel habitats can occur accidentally.
• 3. Concealing details of the location of pearl mussel habitats in publications has an adverse impact on the work of specialists, as they do not have access to enough information to study and analyse the biology and distribution of these molluscs.
• 4. One river with pearl mussels in the Gulf of Finland was initially described anonymously (as ‘River B’). Unfortunately, the river was subject to severe human impact, and the largest aggregation of pearl mussels was almost exterminated in the process of constructing a new electric supply line.
• 5. Concealing information on pearl mussel habitats in the Russian section of the Baltic Sea basin was also shown to have been a poor decision. Although the threat from potential poachers was insignificant because of the low commercial value of pearl mussels, the authorities remained uninformed about the existence of valuable habitats.
• 6. The question of whether the locations of pearl mussel habitats should be concealed or revealed in scientific publications does not have an unambiguous answer and should be considered on a case‐to‐case basis; however, the cases for which disclosure is reasonable seem to be more numerous.

     

Changes in proximate composition,lipid class and fatty acid profile in Greenshell™ mussels (Perna canaliculus) over an annual cycle

Greenshell? mussel (GSM, Perna canaliculus) is New Zealand's most important aquaculture species. This study looked at changes in the proximate composition, lipid class and fatty acid profile of male and female market ready mussels over a year from April 2016 through to March 2017. There were differences over the season as well as differences between male and female mussels. Winter GSM had lower lipid, carbohydrate and protein concentrations than other seasons. Female mussels had a higher lipid (on average 1.8 ± 0.5 g/100 g ww) and carbohydrate (on average 5.0 ± 1.1 g/100 g ww) compared with the males (lipid, 1.5 ± 0.4 g/100 g ww and carbohydrate 4.5 ± 1.2 g/100 g ww). The major differences observed between seasons in the omega 3 and fatty acids content of the GSM were driven by the fat content, with the highest fat content found in female mussels in the spring prior to spawning. The majority of lipids found in mussels are polar lipids. Overall, this study provides the most comprehensive data on the composition and the lipid content of GSM to date and provides solid base‐line data as the New Zealand GSM industry continues to improve their production procedures. The enhanced nutritional payload of mussels harvested outside of winter (particularly female mussels in spring) could drive a differentiated higher value mussel product.     

A cautionary tale about translocating mussels and implications for conservation: A case study from two river basins in central Texas

1. Translocation is used to conserve mussels, yet there remains a debate about its merit owing to poor understating of its effects on transported mussels.
2. This study evaluated survivorship, body condition, and total glycogen and lipids for one common and widely distributed species (Cyclonaias pustulosa), two rare species (Cyclonaias petrina; Lampsilis bracteata), and one species complex (Fusconaia sp. – Fusconaia chunii and Fusconaia flava) from the East Fork of the Trinity River and the Llano River of Texas.
3. Survivorship estimates for C. pustulosa and Fusconaia sp. using the Kaplan–Meier estimator were high in the East Fork. Body condition, glycogen, and total lipids varied for C. pustulosa and Fusconaia sp., which may have indicated a short-term impact. For the Llano, survivorship of C. petrina and L. bracteata was high for the resident treatments but significantly reduced for the translocation treatments.
4. The decline in survivorship for C. petrina was mirrored by decreases in the body condition, which may indicate inability to acclimate to novel environments. For L. bracteata, declines in survivorship were due to predation by Procyon lotor, racoon. A large flood of 3,766 m³ s⁻¹ at the end of the study eliminated both study sites.
5. The findings of this study show that translocating mussels can be successful; however, sublethal effects and mortality may still occur. These effects are rooted in species-specific differences, which is not unexpected because mussel species vary in how they cope with environmental change based on their life-history traits. However, these traits are rarely considered when translocating mussels.
6. To complicate matters, most mussel species have yet to be evaluated on how they respond to translocation, and for species where such information is available, adults are the primary focus. Addressing these knowledge gaps is critical for determining the appropriateness of translocation and improving its efficacy.

     

Biodeposit production and benthic loading by farmed mussels and associated tunicate epifauna in Prince Edward Island

An experimental study was done to evaluate the biodeposition dynamics associated with mussels and two fouling tunicates, Ciona intestinalis and Styela clava, in mussel aquaculture in Prince Edward Island (PEI), eastern Canada. The presence of C. intestinalis on small constructed mussel socks increased biodeposition by a factor of about 2 relative to mussel socks without tunicates. S. clava were small and had a negligible effect on total biodeposition from mussel socks although they increased sedimentation rates relative to that of abiotic control socks. Sinking rates of faecal pellets from large C. intestinalis varied between 1.39 and 6.54 cm s^− 1 (LSMean = 2.35 cm s^− 1). Using biodeposit production and sinking rates and hydrological data obtained in the present study, footprints of benthic loading due to mussel and tunicate biodeposition for a typical mussel farm in PEI were modelled using Shellfish-DEPOMOD. The results show benthic loading below longlines with C. intestinalis to be ca. 2 times greater than those from lines with only mussels with rates of up to 15.2 g m^− 2 d^− 1. However, given the greater settling rate of C. intestinalis biodeposits relative to mussel biodeposits, the extent of the footprint (≥ 1 g m^− 2 d^− 1) is similar or even more restrained.     

Recruitment of the threatened mussel Margaritifera margaritifera in relation to mussel population size,mussel density and host density

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The current distribution and status of the freshwater pearl mussel Margaritifera margaritifera L. 1758 in north-west Ireland

1. Margaritifera margaritifera populations are declining throughout its range, including Ireland, despite legislation designed to protect freshwater pearl mussels and their habitat. 2. A survey of freshwater pearl mussels was carried out on rivers in County Donegal, north-west Ireland, to determine the current distribution, size and density of M. margaritifera populations, as well as to identify potential threats to mussels there. 3. The survey revealed the freshwater pearl mussel to be widespread, particularly in the western half of the county. However, densities of mussels at most sites are low, with just two sites having mussel densities of over 5 m⁻². Furthermore, the species appears to be absent from a number of sites from which it had been previously recorded. 4. According to the literature, there is a long history of pearl fishing in Co. Donegal and neighbouring counties. Evidence from heaps of shells found on the river bed and banks at several sites and recent anecdotal reports from local people suggest pearl fishing is being practised on all rivers investigated during the present study. 5. The main conservation requirements for M. margaritifera populations in Donegal are to maintain water quality at its present high standard and, as pearl fishing appears to be a widespread and immediate threat to the remaining mussel populations, to enforce existing legislation designed to protect M. margaritifera.     

Associations between stream hydrogeomorphology and co‐dependent mussel–fish assemblages: evidence from an Ohio,USA river system

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The status of host fish populations and fish species richness in European freshwater pearl mussel (Margaritifera margaritifera) streams

• 1. The status of host fish populations and fish species richness was investigated at 36 sites of 20 extant freshwater pearl mussel populations, including the drainages of the Elbe, Danube, Rhine, Weser, Aulne, Kemijoki and Tuuloma in Germany, the Czech Republic, France and Finland, by carrying out comparative electrofishings.
• 2. Brown trout (Salmo trutta f. fario) were found to be the available host fish for pearl mussels in all except one of the streams investigated with mean densities of 2861 ha^?1 (range 0–8710 ha^?1) and a mean biomass of 119 kg ha^?1 (range 0–478 kg ha^?1). Streams that had been frequently stocked with brown trout had higher trout biomass and densities of host fish than natural populations, but trout stocking had no positive effect in two of the streams investigated.
• 3. Fish species richness ranged from 2 to 16 species per stream and showed a negative correlation with host fish biomass and host fish densities. Undisturbed oligotrophic pearl mussel headwater streams usually only yielded a low number of fish species. Habitat degradation can reduce competitiveness of specialized trout and result in an increased abundance of ubiquitous or atypical species.
• 4. A link between the lack of juvenile pearl mussels and a lack of suitable host fish was only rarely observed. Functional pearl mussel populations with relatively high numbers of juveniles had significantly lower densities and biomass of host fish than pearl mussel populations without recent recruitment.
• 5. This study suggests that 0+ host fish are not necessarily required to sustain functional pearl mussel populations. Low densities of host fish can be compensated by the higher glochidia carrying capacity of older host fish with limited previous contact with pearl mussel glochidia, by the long reproductive period of mussels, and by low mortality rates of juvenile mussels during their post‐parasitic phase.

Copyright © 2005 John Wiley & Sons, Ltd.     

Prediction of potential freshwater pearl mussel habitat aids in discovery of a large population of Margaritifera laevis in Iturup Island,Russia

1. Freshwater pearl mussels (family Margaritiferidae) are sensitive to human impact and environmental changes. Large declines in their abundance have prompted studies of distribution and estimations of population densities.
2. Iturup Island, a part of Kuril Islands, Russia, is considered to be within the distribution area of freshwater pearl mussels, but this information is based on only two specimens collected several decades ago. Detailed survey of the island is challenging as most of its territory is nearly impassable.
3. A preliminary analysis of island rivers was carried out prior to the surveys to discover potential freshwater pearl mussel habitats. Based on previous experience from European Russia, freshwater pearl mussel habitat was expected to occur in rivers flowing out of lowland lakes.
4. Live individuals of Margaritifera laevis were found during surveys in one river together with the unionid Beringiana beringiana, which were also found in two other rivers where the predicted habitat occurred. Based on prediction and surveys, the occurrence of freshwater pearl mussels in other rivers of Iturup Island is unlikely.
5. Pearl mussels were concentrated in a small section of the Zmeika River with a population of about 100,000 mussels. Present threats to the population include overharvest of host fish masou salmon (Oncorhynchus masou).
6. Surveys using similar methods can help to reveal unknown freshwater mussel populations on other Kuril Islands and on the mainland.

     

Pasteurizing Cold Smoked Salmon (Oncorhynchus nerka): Thermal Inactivation Kinetics of Listeria monocytogenes and Listeria innocua

Listeria monocytogenes results in potential food safety concerns in ready-to-eat refrigerated products. Cold-smoked salmon is a food considered to be at high risk for Listeria spp. contamination for which a mild heat treatment or pasteurization step might be helpful to reduce microbial levels. Cold-smoked salmon was inoculated with a cocktail of four strains (L. monocytogenes: ATCC19114, 7644, and 19113, and L. innocua: ATCC51742) and inactivation curves obtained at 58, 60, 62, 64, and 66°C using capillary tube methods. Inactivation results showed typical log linear trends (R² ≥ 0.97). D-values of L. monocytogenes and L. innocua were 0.3 to 14.1 min at 66 to 58°C, with a z-value of 5.2 to 6.5°C and activation energy of 332 to 414 kJ/mol. The nonpathogenic Listeria innocua ATCC51742 had comparable D- and z-values to the three strains of L. monocytogenes and thus can be used for validation of pasteurization processes to control L. monocytogenes in cold-smoked salmon and potentially other ready-to-eat thermolabile food products.     

Product differentiation,labelling and quality approach: Developments and stakes in the French shellfish market

Abstract

France is one of the world's top producers of oysters and mussels by aquaculture with 140 000 tonnes of oysters, 60 000 tonnes of mussels and an ex‐farm turnover accounting to 350 million US$ in 1996. The French market is by far the largest in Europe for oysters and is supplied entirely by domestic production, with very little external trade. Conversely, the French market for mussels is a very competitive one, widely open to imports. Given the evolution of market conditions due to the development of supermarkets, to the competition of new value‐added products and to the modification of consumer habits, French oyster and mussel producers have begun to implement various strategies of product differentiation and quality approach. These numerous strategies, which are built on geographical origin, process of production or marketing promotion may induce confusion in the consumer's mind. A typology of these strategies has been drawn in order to clarify the situation and to assess their sustainability. Since any quality approach has a counterpart in terms of production costs, an enquiry has been carried out at the level of supermarkets in order to assess the price the buyers are ready to pay for labelled oysters and mussels. The results of this study show important variations according to the locality of the supermarkets, especially with regard to the distance to the coast and the size of the town. Contractual relationships between producers and supermarkets as well as better production organization prove to be important perquisites to ensure successful product differentiation and quality approaches.