Proteolysis and Its Control Using Protease Inhibitors in Fish and Fish Products: A Review.

Texture is one of the food quality attributes affecting the consumer's acceptability and the market value. Fish and shellfish undergo weakening or softening of muscle, particularly during extended storage under inappropriate conditions. The phenomenon is governed by endogenous proteases, both digestive and muscle proteases. Proteases present in the gastrointestinal tract that leach out to muscle tissue can induce proteolysis of myofibrillar and collagenous proteins. Furthermore, the muscle proteins present in gels fabricated from fish or shellfish meat also encounter degradation during thermal processing. Endogenous heat-activated proteases strongly bind to muscle proteins and are activated during heating, thereby degrading myofibrillar proteins, which are abundant in muscle tissue. This deterioration of the proteins directly leads to a weakened gel with poor water-holding capacity. Both cysteine and serine proteases are responsible for the degradation of myofibrillar proteins in several aquatic animals. Effective pretreatment of fish and shellfish, as well as the use of food-grade protease inhibitors (PIs), have been implemented to inactivate endogenous muscle and digestive proteases. For this review, proteolysis of muscle proteins and its control by food-grade PIs are revisited. Improved and effective lowering of proteolysis should be gained, thereby maintaining the quality of fish and their products.

Mackerel and Seaweed Burger as a Functional Product for Brain and Cognitive Aging Prevention.

Most world countries are experiencing a remarkable aging process. Meanwhile, 50 million people are affected by Alzheimer's disease (AD) and related dementia and there is an increasing trend in the incidence of these major health problems. In order to address these, the increasing evidence suggesting the protective effect of dietary interventions against cognitive decline during aging may suggest a response to this challenge. There are nutrients with a neuroprotective effect. However, Western diets are poor in healthy n-3 polyunsaturated fatty acids (n-3 PUFAs), such as docosahexaenoic acid (DHA), iodine (I), and other nutrients that may protect against cognitive aging. Given DHA richness in chub mackerel (Scomber colias), high vitamin B9 levels in quinoa (Chenopodium quinoa), and I abundance in the seaweed Saccorhiza polyschides, a functional hamburger rich in these nutrients by using these ingredients was developed and its formulation was optimized in preliminary testing. The effects of culinary treatment (steaming, roasting, and grilling vs. raw) and digestion on bioaccessibility were evaluated. The hamburgers had high levels of n-3 PUFAs in the range of 42.0-46.4% and low levels of n-6 PUFAs (6.6-6.9%), resulting in high n-3/n-6 ratios (>6). Bioaccessibility studies showed that the hamburgers could provide the daily requirements of eicosapentaenoic acid (EPA) + DHA with 19.6 g raw, 18.6 g steamed, 18.9 g roasted, or 15.1 g grilled hamburgers. Polyphenol enrichment by the seaweed and antioxidant activity were limited. The hamburgers contained high levels of Se and I at 48-61 µg/100 g ww and 221-255 µg/100 g ww, respectively. Selenium (Se) and I bioaccessibility levels were 70-85% and 57-70%, respectively, which can be considered high levels. Nonetheless, for reaching dietary requirements, considering the influence of culinary treatment and bioaccessibility, 152.2-184.2 g would be necessary to ensure daily Se requirements and 92.0-118.1 g for I needs.

Nutritional quality traits of Mediterranean mussels (Mytilus galloprovincialis): A sustainable aquatic food product available on Italian market all year round.

In this study, Mediterranean mussels (Mytilus galloprovincialis) coming from Italian production were purchased in the most important Italian wholesale fish market in different seasons. Biometrical parameters and chemical composition were investigated, with a particular focus on lipid quality and fatty acids (FAs) composition. Results showed a valuable nutritional profile independently by the season of production, represented by high protein and low-fat content, with the lipid portion represented by high amounts of beneficial FAs, particularly the long chain of the n-3 series. Some differences (p < 0.05) were found in carbohydrates and fat content of mussels edible tissues and in FAs profile of specimens collected in different seasons. The most favourable composition in terms of lipid quality was found in mussels collected during spring, corresponding to the moment of the year when mussels store energy reserves in the form of carbohydrates and fat (preparing for the spawning events) and when seawater is enriched in phytoplankton. The lipid health indices calculated (n6/n3, AI, TI) showed optimal values independently by the season of production. The outcomes obtained in this study could help supporting the appreciation of Mediterranean mussels as nutritional valuable seafood product, thus helping encouraging their consumption and promoting the appraisal of this farming sector essential for Italian aquaculture and related to low environmental impact.

Effects of different cooking methods on the proximate composition and physical properties of Brown shrimp (Metapenaeus dobsonii) during cooking and freezing cycle.

Present study aimed to evaluate the changes in proximate composition and physical attributes in brown shrimp (Metapenaeus dobsonii) exposed to different methods of cooking followed by freezing. For this, three different grades (100/200, 200/300, and 300/500 numbers per kg) of brown shrimp were cooked at 90°C till the core temperature of the product reaches 85°C using hot water, steam, and microwave (400W) techniques. The changes in yield, cooking loss, proximate composition, textural, and colour profile were assessed for cooked shrimps. The cooking loss was higher for larger grades of shrimp, whereas shrimp cooked using hot water exhibited the highest cooking loss. Lowest cooking loss was observed for microwave-cooked shrimp. Moisture content decreased after cooking whereas protein, fat, ash, and calorie content increased. After cooking, different grades of shrimp showed an increase in their lightness (L*), redness (a*), and yellowness (b*) values. The smaller grade shrimp exhibited lower value for cohesiveness, hardness, chewiness, and gumminess. Different cooking techniques yielded cooked shrimp of varying hardness values.

Cold smoking of Lebranche mullet (Mugil liza): Physicochemical, sensory, and microbiological evaluation.

The suitability of Mugil liza for cold smoking was evaluated and the effect of four different salting treatments on physicochemical, microbiological, and sensory characteristics was assessed. The addition of sucrose (3%) and acetic acid (0.5%) to the brine lead to fillet dehydration with lower NaCl penetration, combined with higher reduction of pH. Brining at refrigerated temperature (5 ± 1 ℃) instead of room temperature (16 ± 2 ℃) was more effective in preventing microbial growth. Loads of bacterial groups assessed in all smoked samples were below 100 CFU/g and the aw, moisture, NaCl, and pH values achieved were within the typical stability range of smoked fish products. The obtained products were characterized by the smoked aroma and salty taste, differing in 7 of the 21 evaluated descriptors. The use of acetic acid in brine formulation showed an effect over color and texture descriptors. The affective test indicated the overall acceptability of products, being preferred the samples treated in the lowest NaCl concentration (5%).

Protein Oxidation in Muscle Foods: A Comprehensive Review.

Muscle foods and their products are a fundamental part of the human diet. The high protein content found in muscle foods, as well as the high content of essential amino acids, provides an appropriate composition to complete the nutritional requirements of humans. However, due to their special composition, they are susceptible to oxidative degradation. In this sense, proteins are highly susceptible to oxidative reactions. However, in contrast to lipid oxidation, which has been studied in depth for decades, protein oxidation of muscle foods has been investigated much less. Moreover, these reactions have an important influence on the quality of muscle foods, from physico-chemical, techno-functional, and nutritional perspectives. In this regard, the loss of essential nutrients, the impairment of texture, water-holding capacity, color and flavor, and the formation of toxic substances are some of the direct consequences of protein oxidation. The loss of quality for muscle foods results in consumer rejection and substantial levels of economic losses, and thus the control of oxidative processes is of vital importance for the food industry. Nonetheless, the complexity of the reactions involved in protein oxidation and the many different factors that influence these reactions make the mechanisms of protein oxidation difficult to fully understand. Therefore, the present manuscript reviews the fundamental mechanisms of protein oxidation, the most important oxidative reactions, the main factors that influence protein oxidation, and the currently available analytical methods to quantify compounds derived from protein oxidation reactions. Finally, the main effects of protein oxidation on the quality of muscle foods, both from physico-chemical and nutritional points of view, are also discussed.

The development of isomer-specific analysis of branched 4-nonylphenol in food for dietary exposure - a critical review of analytical methods and occurrence in foodstuffs.

4-Nonylphenol (4-NP) is a para-substituted phenolic compound comprising a straight or branched carbon chain group while branched 4-NP consists of 211 possible structural isomers. NP is recognised as an environmental pollutant and exists ubiquitously in both the environment and in food. 4-NP, especially branched 4-NP, has been shown to have the potential role of endocrine disruptor and xeno-oestrogen. Moreover, different NP isomers also exhibit different oestrogen-like activities. Recently, it was reported that the isomer-specific profile of 4-NP in foodstuffs varies greatly between and within food groups. Hence, risk assessment based on total branched 4-NP cannot reflect dietary risk. This study reviews the analytical methods applicable to conduct an isomer-specific analysis of 4-NP and its occurrence in foodstuffs. Lastly, research gaps are identified for future research.

Effect of food processing (fish burger preparation and frying) on residual levels of enrofloxacin and ciprofloxacin.

The influence of fish burger preparation and frying on residual levels of enrofloxacin (ENR) and ciprofloxacin (CIP) was evaluated. For this purpose, a high-throughput liquid chromatography-mass spectrometry analytical method for the quantitation of ENR and CIP residues in tilapia products (fillet, raw fish burger and fried fish burger) was developed and validated based on European and Brazilian guidelines. Sample preparation was accomplished by extraction with acidified acetonitrile followed by clean-up with hexane. Chromatographic analysis was performed on a C18 column using isocratic elution with 0.1% formic acid and acetonitrile (85:15 v:v). The analytical method showed suitable performance to quantify the residual levels of ENR and CIP in the studied matrices. No reduction in the residual levels of ENR and CIP was observed during fish burger preparation and only a 10% reduction occurred as a consequence of frying, indicating that both compounds were stable to the preparation of the fish burger and to frying conditions.

Effect of thyme and oregano essential oils on the shelf life of salmon and seaweed burgers.

The effect of different essential oils on the quality and shelf life of fish and seaweed burgers during storage was evaluated. For this purpose, thyme and oregano essential oils were selected at a concentration of 0.05% (v/w). Three types of salmon and seaweed burgers were prepared: without essential oil, burgers with red thyme essential oil (0.05% (v/w)) and burgers with oregano essential oil (0.05% (v/w)), which were vacuum packaged and stored at 4 ℃ for 17 days. Physicochemical and microbiological analyses were carried out periodically throughout storage. The addition of both essential oils did not have any effect on the evolution of the pH, the moisture content or texture parameters. Only the thyme essential oil managed to slightly slow down the increase of total volatile basic nitrogen and trimethylamine nitrogen. The samples with oregano essential oil and especially those with thyme essential oil showed minor oxidation. The salmon and seaweed burgers without essential oils and those which contained oregano essential oil showed a faster increase of mesophilic counts than those which had thyme essential oil, but no noticeable improvement was observed in the shelf life of the burgers with thyme essential oil. To improve the shelf life of the fish and seaweed burgers, it would be necessary to increase the concentration of both essential oils.

Heavy metals and PAHs in canned fish supplies on the Serbian market.

The aim of this study was to determine the level of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in 57 samples of canned tuna, 25 samples of canned sardines, and 16 samples of canned smoked sprouts, collected from supermarkets in Serbia. Heavy metal levels (lead, cadmium, mercury, arsenic, iron, copper, and zinc) were determined using an inductive coupled plasma mass spectrometry method. Sixteen analysed PAHs were determined using a gas chromatography-mass spectrometry method. The trace elements in canned fish were in the range (mg kg-1) of 0.01-0.28 for lead, 0.003-0.08 for cadmium, 0.007-0.64 for mercury, 0.17-3.73 for arsenic, 3.88-52.2 for iron, 0.2-5.95 for copper, and 1.35-44.5 for zinc. Total PAH levels reached 17.67 µg kg-1 in canned tuna and 15.12 µg kg-1 in sardines, whereas in smoked sprouts it amounted to 57.19 µg kg-1. Some of the samples contained cadmium, arsenic, copper, and benzo(a)pyrene above the limits as set by the European and Serbian legislation.

A fit-for-purpose method to monitor 16 European Union PAHs in food: results of five years of official food control in two Italian regions.

A gas-chromatographic single-quadrupole analytical method for the analysis of the 16 priority European Union (EU) polycyclic aromatic hydrocarbons (PAHs) in food is presented. The method fulfils the request of Regulation EU 836/2011 for an analytical procedure to be used for official control of PAHs in food in EU member states. The sample preparation involves a pressurised liquid extraction (PLE) with an in-cell clean-up step followed by a lipid removal using solid-phase extraction (SPE) on a styrene divinylbenzene stationary phase (SDVB) and a final gel-permeation chromatography (GPC) step. To reach a better sensitivity for all the analytes, including the heaviest last eluting PAHs, 3 µl of the purified extract were injected in solvent vent mode using a programmable temperature vaporization (PTV) injector. The isobaric PAH isomers were successfully separated using an Agilent Technologies DB-17MS (20 m × 0.18 mm × 0.18 µm) column. The method was fully validated using an in-house approach and the sensitivity, accuracy and precision obtained were satisfactory. The method expanded uncertainty was estimated and it was verified that it was below the maximum standard measurement uncertainty. Moreover, the results of 347 samples of meat and meat products, fish and fish products and mussels collected from January 2012 to December 2016 in the Marche and Umbria regions of Italy are reported. None of the samples exceed the maximum levels fixed by EU Regulation 835/2011, and clams turned out to be the most contaminated among the food matrices analysed. Finally, an estimate of the sum of four marker PAHs (benzo[a]anthracene, benzo[b]fluoranthene, benzo[a]pyrene, chrysene) as indicator of the PAHs contamination was done by comparison with the 16 carcinogenic PAHs sum.

Risk assessment of dietary exposure to tryptamine for the Austrian population.

Tryptamine acts as a neuromodulator and vasoactive agent in the human body. Dose-response data on dietary tryptamine are scarce and neither a toxicological threshold value nor tolerable levels in foods have been established so far. This paper reviews dose-response characteristics and toxicological effects of tryptamine as well as tryptamine contents in food, estimates dietary exposure of Austrian consumers, and calculates risk-based maximum tolerable limits for food categories. A dose without effect of 8 mg kg-1 body weight day-1 was derived from literature data. Dietary exposure via fish/seafood, beer, cheese and meat products was estimated for Austrian schoolchildren, female and male consumers, based on 543 food samples analysed in Austria 2010-15 and on food consumption data from 2008. Even worst-case estimates based on very high tryptamine contents reported in the literature did not exceed 5.9 mg kg-1 body weight day-1, and thus were below the dose without effect. Maximum tolerable levels for food commodities were calculated for high-consumption scenarios (95th percentile of female Austrian consumers). For fresh/cooked fish, preserved fish, cheese, raw sausage, condiments, sauerkraut and fermented tofu, maximum tolerable levels were 1650, 3200, 2840, 4800, 14,120, 1740 and 2400 mg kg-1, respectively. For beer, the maximum tolerable limit of 65 mg kg-1 included an uncertainty factor of 10. None of the Austrian occurrence data exceeded these levels (in fact, only 3.3% of samples demonstrated measurable amounts of tryptamine), and just one report was found in the literature on a raw fish sample exceeding the respective tolerable level. In sum, dietary intake of tryptamine should not cause adverse health effects in healthy individuals. The assessment did not take into account the combined effects of simultaneously ingested biogenic amines, and increased susceptibility to tryptamine, e.g., due to reduced monoamine oxidase activity.

Organochlorine pesticides in canned tuna and sardines on the Serbian market.

The aim of this study was to determine the level of organochlorine (OC) pesticides in 57 samples of canned tuna and 31 samples of canned sardines in vegetable oil, collected from supermarkets in Serbia. OC pesticides α-HCH, ß-HCH, δ-HCH, dichlorodiphenyltrichloroethane (DDT), DDE, DDD, dielderin, endosulfane I, endosulfane II, endosulan sulfate, endrin, endrin ketone, heptachlor, heptachlor epoxide, lindane, aldrin, metoxichlor, cis-chlordane and trans-chlordane were determined using a GS-MS method. The highest concentrations (µg kg-1, arithmetic means) in canned tuna were for δ-HCH (60.6 ± 97.0) and p, p´-DDT (55.0 ± 25.1), while the corresponding values in canned sardines were for δ-HCH (90.7 ± 102.7) and endosulfane II (78.0 ± 145.9). Mean level for the sum of endosulfans was above the maximum limit in canned sardines (85.0 µg kg-1). Also, dieldrin (39.7 µg kg-1) was measured above the ML.

Muscle temperature at the point of filleting--Subsequent effect on storage quality of prerigor filleted raw- and cold-smoked Atlantic salmon.

The impact of increased muscle temperature at the point of filleting on fillet quality of raw- and cold-smoked Atlantic salmon was investigated. Commercially reared fish (5.65 kg, Kf: 1.23, pH: 7.29, muscle temperature: 6.68 ℃) were killed and immediately tempered in three different containers. Muscle temperatures after filleting (<3 h postmortem) of the three groups were 2.08 ℃ (hereafter named T-2); 9.07 ℃ (hereafter named T-9), and 14.09 ℃ (hereafter named T-14), respectively. The pH after filleting was significantly low for T-14 (6.93) followed by T-9 (7.06) and T-2 (7.22). Raised temperature at point of filleting was found to significantly alter development of rigor mortis, which subsequently affected muscle pH and the reflective properties of the fillet surface during 14 days' ice storage. Of cold-smoked fillets, however, a more distinct effect of raised temperature was observed on visual perception resulting in lighter and more yellowish cold-smoked fillets after 14 days' storage. In addition, raised temperature also affects the development of muscle pH in cold-smoked fillets during refrigerated storage. No effects of raised muscle temperature were found regarding drip loss, water-holding capacity, or fillet firmness either for raw- or cold-smoked fillets throughout the storage period.

Survey of polycyclic aromatic hydrocarbons in marine products in Korea using GC/MS.

This study investigates polycyclic aromatic hydrocarbons (PAHs) in marine products on the Korean market. A total of 280 samples of fish (n = 100), shellfish (n = 80), cephalopod (n = 60) and crustacea (n = 40) were collected for analyses of PAHs (naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-c,d]pyrene, dibenz[a,h]anthracene and benzo[g,h,i]perylene). The analytical procedure was based on the matrix solid-phase dispersion on Florisil cartridges and extraction with hexane/dichloromethane (3:1, v/v). The PAHs were determined by gas chromatography with mass spectrometric detection using selective ion monitoring. Average recoveries for all the PAHs studied were in the range 58-79%. The sum of 16 PAHs concentrations in fish, shellfish, cephalopod/crustacea were in the range 0.2-0.5, 1.2-1.6 and 0.8-1.9 µg/kg, respectively.

The influence of industrial-scale canning on cadmium and lead levels in sardines and anchovies from commercial fishing centres of the Mediterranean Sea.

The current study encompassed a survey on the levels of toxic trace elements in two highly consumed fish species in commercial fishing centres of western, central and eastern Mediterranean Sea. A Zeeman GTA-AAS graphite furnace atomic absorption spectrometry system was used throughout the study. Toxicological evaluation of the samples revealed a low Cd content in the raw samples, ranging between 0.003 and 0.027 mg kg⁻¹. Pb presented significantly higher values, from 0.037 to 0.297 mg kg⁻¹, occasionally reaching the limit of 0.3 mg kg⁻¹. Heavy metal levels were particularly higher in bones, thus raising queries about the safe consumption of fish intended to be eaten as a whole, a very common practice for small fish and canned products. The influence of industrial-scale canning showed that canning enhanced heavy metal levels by 35%-80%. The effect of canning depended on metal type and reduction of moisture loss after the steam-roasting step of the canning procedure.

Total mercury, methylmercury and ethylmercury in marine fish and marine fishery products sold in Seoul, Korea.

In 2009, a survey of 177 samples of fish and fishery products from the markets in Seoul was carried out to investigate total mercury and organic mercury (methylmercury) concentrations and to establish a correlation, if any, between total and organic mercury levels. Concentrations of total and organic mercury in canned tuna ranged 0.001-2.581 and 0.003-1.307 mg/kg, respectively; those for fish, such as cod or salmon, ranged 0.012-2.529 and 0.021-0.507 mg/kg, respectively. Ethylmercury was not detected. More than 50% of total mercury in the samples existed as organic mercury. The correlation coefficients (r(2)) between total mercury and methylmercury concentrations of fish and fishery products found to have methylmercury were 0.844 and 0.976, respectively, which was statistically significant. There was a higher correlation in fishery products than in fish. Although there was no product in which mercury exceeded the standard set by the Food Code in 2008, with the exception of marlin steak, a processed food, which contained 1.307 mg/kg methylmercury. None exceeded the provisional tolerable weekly intake (PTWI) for mercury. Collectively, the results indicate that fish or fishery products marketed in Seoul, with the exception of marlin, have low levels of total or organic mercury and, thus, intake of these products is not a risk to public health.

Survey of lead, cadmium, mercury and arsenic in seafood purchased in Campania, Italy.

Lead, cadmium, mercury and arsenic were surveyed in fresh catch, farmed and frozen marine fish, cephalopods and mussels marketed in Campania (Italy), and the population's weekly intake from seafood was assessed. A total of 162 specimens of fish and cephalopods and 30 pools of mussels were analyzed. Pb levels in fresh catch species ranged between <20 and 689 ng/g; in farmed from <20 to 438 ng/g and in frozen from <20 to 541 ng/g. Cd values ranged in fresh catch seafood from <0.8 to 19.8 ng/g; in farmed from <0.8 to 42.3 ng/g; in frozen from <0.8 to 93.1. Hg levels ranged 8-339 ng/g in wild seafood; <5-226 ng/g in farmed and <5-313 ng/g in frozen. In fresh catch seafood, As values ranged <10-231 ng/g; in farmed from 12-310 ng/g and in frozen 12-272 ng/g. Cd and Hg concentrations were below the EU limits in all species; two samples of farmed European seabass and two frozen samples exceeded EU limits for Pb. The median weekly dietary intake could affect the provisional tolerable weekly intake (PTWI) of Pb by 2% (range 0.5-16.5%), Cd PTWI by 0.9% (range 0.1-8.0%), Hg PTWI by 9.6% (range 0.6-41.0%) and the As PTWI by 3.6% (range 0.4-12.5%). Considering the upper values in the ranges, seafood represents a non-negligible contribution to Pb weekly intake (16.5%), but mainly to the weekly intake of Hg (41.0%) for high seafood consumers and those consuming the most contaminated species.

Survey and risk assessment of trace elements in foods from Taiwan containing red mould rice (Monascus) by ICP-MS.

The concentrations of seven trace elements (As, Cd, Cr, Pb, Se, Cu and Zn) in 93 red mould rice (Monascus) food samples in Taipei, Taiwan, were determined by inductively coupled plasma-mass spectrometry (ICP-MS) after wet digestion. The results, calculated in mg kg(-1) (wet weight) for each sample, revealed the general scenario of food safety in Taiwan: As (0.005-12.04), Cd (<0.0005-2.22), Cr (0.014-6.95), Cu (0.012-8.70), Pb (0.001-0.64), Se (<0.001-1.29) and Zn (0.020-67.02). Three food samples were identified with As concentrations higher than regulatory limits: a dietary supplement sample and a seaweed sample with As concentrations that exceeded the limit of Taiwan's health food standard of 2 mg kg(-1), and a canned eel sample with an As concentration that exceeded the limit of Canada's fish standard of 3.5 mg kg(-1). This study suggests that the estimated intakes of these seven trace elements from the consumption of foods containing Monascus pose little risk, as the trace element contents in the majority of samples were lower than the permissible/tolerable intakes per week according to the guidelines recommended by the Food and Agricultural Organization/World Health Organization (FAO/WHO). Moreover, their concentrations in foods containing Monascus differ widely for different food varieties, suggesting that external contaminants and raw materials are the main sources of trace elements. This study shows that ICP-MS is a simple method proposed for the determination of As, Cd, Cr, Pb, Se, Cu, and Zn in foods containing Monascus.