Growing fish consumption worldwide has driven fish processors to introduce innovative seafood products with extended shelf-life and desirable organoleptic properties. This study investigates the impact of freezing deep-skinned Atlantic mackerel fillets before and after smoking, prior to canning. Physicochemical and organoleptic properties of canned fillets were evaluated after 1 and 12 months of storage at room temperature. The formation of primary oxidation products (PV) was similar in both cases, while the secondary oxidation products (TBARS) were significantly lower when the fillets were smoked before freezing. PV and TBARS were significantly lower in all canned mackerel samples after prolonged canned storage compared to the shorter storage. However, lipid oxidation and hydrolysis were very limited after both treatments and, therefore, do not constitute an issue in these products. Results of product evaluation and instrumental texture analysis of canned mackerel indicated more beneficial characteristics (firmer fillets, nor mushy) when fillets were frozen first and then hot-smoked (FSC). Fillets that were smoked first and then frozen (SFC), regardless of the canning storage time, were characterized by a mushy texture and appearance, which can negatively impact consumer acceptance. Therefore, freezing prior to hot-smoking may represent a better choice if the fillets are intended for canning.
Author: Kristín Edda Gylfadóttir
Analysis of volatile compounds in various marine resources and seafood during storage has shown that compounds derived from oxidation of polyunsaturated fatty acids are responsible for the characteristic fish odor. Their origin and formation have been partially elucidated, where membrane bound phospholipids play a key role as precursors. Volatile microbial metabolites as indicators of spoilage can be monitored to determine the quality of fish products. Profiles of volatiles offer possibilities to perform multivariate prediction of quality. However, different handling and processing influences the proliferation of volatiles, depending on the dominating specific spoilage organisms and oxidative processes during storage. As a result, varying levels of volatiles develop in different marine resources and seafood causing different characteristic aromas. Here are some examples to demonstrate the role of key volatile compounds in odor quality changes in chilled cod and haddock, boiled cod, and in washed cod model system. Additionally, the influence of processing on key volatiles and odor development in smoked salmon and salted cod are presented, and key volatiles of seaweed contributing to characteristic marine flavors are highlighted.
An uncharacterized gene encoding a glycoside hydrolase family 43-like enzyme from Clostridium boliviensis strain E-1 was identified from genomic sequence data, and the encoded enzyme, CbE1Xyn43-l, was produced in Escherichia coli. CbE1Xyn43-l (52.9 kDa) is a two-domain endo-β-xylanase consisting of a C-terminal CBM6 and a GH43-like catalytic domain. The positions of the catalytic dyad conserved in GH43, the catalytic base (Asp74), and proton donor (Glu240) were identified in alignments including GH43-enzymes of known 3D-structure from different subfamilies. CbE1Xyn43-l is active at pH 7.0–9.0, with optimum temperature at 65°C, and a more than 7 days' half-life in irreversible deactivation studies at this temperature. The enzyme hydrolyzed birchwood xylan, quinoa stalks glucuronoarabinoxylan, and wheat arabinoxylan with xylotriose and xylotetraose as major hydrolysis products. CbE1Xyn43-l also released xylobiose from pNPX2 with low turnover (kcat over 0.044 s−1) but was inactive on pNPX, showing that a degree of polymerization of three (DP3) was the smallest hydrolyzable substrate. Divalent ions affected the specific activity on xylan substrates, which depending on the ion could be increased or decreased. In conclusion, CbE1Xyn43-l from C. boliviensis strain E-1 is the first characterized member of a large group of homologous hypothetical proteins annotated as GH43-like and is a thermostable endo-xylanase, producing xylooligosaccharides of high DP (xylotriose and xylotetraose) producer.
This article explores long-standing symbiotic relationships between women and microbes in Iceland while analyzing the transformation of this relationship in the making of the dairy product skyr during the twentieth and twenty-first centuries. In the past, differences in microbial cultures and production methods meant that the taste and texture of milk varied greatly. Standardization and technological innovations have steadily impoverished its microbial diversity over the past 120 years. Starting from a historical account of skyr making, we zoom in on skyr in the twenty-first century, a period in which skyr has had an international breakthrough, captured in branding efforts and advertising campaigns produced in this decade for various types of skyr from producers in Iceland, Europe and the United States.
The suitability of using sunflower and rapeseed oils, and water as media for the canning of smoked fillets from Atlantic mackerel (Scomber scombrus) caught during feeding migration was investigated. Physicochemical and sensory changes were evaluated after one month of storage at room temperature. The aqueous medium in the cans led to significantly higher water content and lower salt content than when sunflower or rapeseed oil was used, indicating that while additional water was absorbed by the fillets, salt was leached due to the cook-out effect during sterilization and storage . Using sunflower oil, regardless of the ratio, resulted in better retention of the traditional and desired smoky odor and flavor, and preserved the juicy and tender texture of the fillets better than when rapeseed oil was used. Fillets canned in water exhibited a significantly lower salty flavor and fat-in-mouth attribute than those canned in vegetable oils. While there were only minor differences in the overall sensory parameters between treatments, the variation in salty flavor and fat-in-mouth feeling are crucial due to their significant impact on consumer acceptance. Therefore, using water as a medium is suggested as a favorable option for canning deep-skinned and smoked fillets from well-fed Atlantic mackerel.
Shrimp feed formulations have moved towards less fish meal and more of the readily available and cheaper plant proteins. To counteract the lower attractiveness and palatability of plant proteins, feeds are supplemented with ingredients known to have chemoattractive properties that will increase feed intake. This study investigated the putative chemoattractive effect of Calanus finmarchicus hydrolysate, when used as a dietary supplement in shrimp feeds. C. finmarchicus is a zooplankton species native to the northern Atlantic Ocean and is a novel and sustainable raw material for shrimp feed products. Diet attractiveness was evaluated in a 24-day feeding trial with whiteleg shrimp (Litopenaeus vannamei) by measuring the intake of 12 diets with various levels of fish meal, calanus hydrolysate, and krill (Euphausia superba) meal. Higher inclusion rates of both ingredients resulted in increased feed intake, and supplementing the high fish meal diet with calanus hydrolysate gave a statistically significant higher feed intake. Low molecular weight peptides, chemoattractive amino acids, and the water-soluble nature of the hydrolysate could explain the chemoattractive properties observed in the study.
The marine environment, contains abundant renewable resources, eg macroalgae with unique polysaccharides, motivating the search for enzymes from marine microorganisms to explore conversion possibilities of the polysaccharides. In this study, the first GH17 glucanosyltransglycosylase, MlGH17B, from a marine bacterium (Muricauda lutaonensis), was characterized. The enzyme was moderately thermostable with Tm at 64.4 °C and 73.2 °C, but an activity optimum at 20 °C, indicating temperature sensitive active site interactions. MlGH17B uses β-1,3 laminari-oligosaccharides with a degree of polymerization (DP) of 4 or higher as donors. Two glucose moieties (bound in the aglycone +1 and +2 subsites) are cleaved off from the reducing end of the donor while the remaining part (bound in the glycone subsites) is transferred to an incoming β-1,3 glucan acceptor, making a β-1,6-linkage, thereby synthesizing branched or kinked oligosaccharides. Synthesized oligosaccharides up to DP26 were detected by mass spectrometry analysis, showing that repeated transfer reactions occurred, resulting in several β-1,6-linked branches. The modeled structure revealed an active site comprising five subsites: three glycone (−3, −2 and −1) and two aglycone (+1 and +2) subsites, with significant conservation of substrate interactions compared to the only crystallized 1,3- β-glucanosyltransferase from GH17 (RmBgt17A from the compost thriving fungus Rhizomucor miehei), suggesting a common catalytic mechanism, despite different phylogenetic origin, growth environment, and natural substrate. Both enzymes lacked the subdomain extending the aglycone subsites, found in GH17 endo-β-glucanases from plants, but this extension was also missing in bacterial endoglucanases (modeled here), showing that this feature does not distinguish transglycosylation from hydrolysis, but may rather relate to phylogeny.
This study was undertaken to evaluate the effects of liquid smoked flavorings and wood smoke on the sensory, color, texture, and lipid stability of smoked mackerel fillets for four weeks chilled storage. Fish fillets were smoked by two methods: (1) immersed in brine (1:1) containing 100 g/L NaCl at 0-5 °C for 3 hours, allowed to drain at room temperature (~20 °C) for 2 hours and smoked directly with wood smoke in a smoking chamber at 25 °C for 3 hours; (2) immersed in brine (1:1) containing 5 mL/L commercial liquid smoke flavorings and 60 g/L NaCl for 16 hours at 0-5 °C then dried at 25 °C for 2 hours in an oven. Smoked samples were then vacuum packed and stored chilled at -1 °C for one week, followed by 4±1 °C for three weeks. The quality changes in sensory, color, texture, and lipid stability were observed after 0, 1, 2, 3 and 4 weeks of storage. The results showed that, smoked mackerel using commercial liquid smoked flavorings was higher in rancid flavor, lightness, redness, and yellowness but had less bitter odor and was softer than the wood smoked mackerel. The lipid oxidation was higher after the wood smoke process but was however rather stable during the chilled storage. In contrast, lipid oxidation in the liquid smoked products increased significantly during chilled storage.
Abstract
Background
Health authorities are increasingly integrating environmental sustainability considerations into food-based dietary guidelines. However, concerns persist about the accuracy of the data used to assess environmental impacts, as well as the extent to which these guidelines are followed in practice.
Aim
To compare dietary greenhouse gas (GHG) emissions estimates using different top-down and bottom-up life cycle assessment (LCA) databases; and to estimate GHG emissions of food consumption within the ranges set for meat and dairy in recently proposed environmentally sustainable diets.
Methods
Dietary GHG emissions were estimated for participants in the 2019–2021 Icelandic National Dietary Survey (n = 822) using three publicly available LCA databases from Denmark, the US, and France. GHG emissions among participants whose consumption was aligned with the EAT-Lancet diet, the 2021 Danish food-based dietary guidelines and the 2023 Nordic Nutrition Recommendations were also quantified.
Results
The mean dietary GHG emissions among participants were 6.3, 6.1, and 6.1 kg CO2-eq/day based on the Danish (top-down), US (bottom-up), and French (bottom-up) databases, respectively. The relative ranking of foods was also consistent across all three databases. For example, the relative contribution of total CO2-eq (% range for the three databases) was highest for red meat (39–51%), followed by dairy (10–17%) and beverages (9–13%). The contribution from plant-based foods (6–10%), seafood (4–11%), and poultry/eggs (<5%) was modest. The dietary habits of most participants (86%) were outside the ranges for meat and dairy consumption as set by the three sustainable diets. However, participants reporting consumption within the ranges for meat and dairy had mean GHG emissions ranging between 4.2 and 4.7 kg CO2-eq/day, depending on the diet. In comparison, the mean for participants not adhering to the sustainable diets was 7.7 kg CO2-eq/day. These results are higher than those reported in other Nordic and European studies, likely due to high consumption of lamb, beef, and dairy, and low consumption of plant-based food.
Conclusion
All three LCA databases provided similar estimates for total dietary GHG emissions and relative ranking of different food groups. Based on current dietary habits in Iceland, adherence to environmentally sustainable diets would lead to a substantial reduction in dietary GHG emissions.
The study aimed to evaluate the effects of onboard refrigerated seawater (RSW) storage of whole ungutted cod on the quality parameters of fillets. The reference group was directly gutted, bled, and stored in ice, while three experimental groups were gill-cut, bled, and stored ungutted in an onboard RSW tub at −1.5°C for 24, 60, and 84 hours. The results showed a difference between groups with extended RSW storage leading to negative effects such as increased gaping, bile spots, TVB-N levels, and bacterial growth after 60 hours. Conversely, the 24-hour RSW group closely resembled the quality parameters of the reference group.