Influence of hot-smoking on the stability of fresh and frozen-thawed deep-skinned Atlantic mackerel fillets during cold storage

Atlantic mackerel (Scomber scombrus) caught during the summer months in Icelandic waters after intensive feeding is rich in lipids and, thus, sensitive to lipid degradation. Recent studies have led to improved cooling and handling on board, ensuring high-quality raw material. However, studies on the development of high-quality products for human consumption are lacking. The study aimed to investigate the effects of hot-smoking on the physicochemical, microbial, and sensory quality of deep-skinned Atlantic mackerel fillets during chilled storage (1 ± 0.6°C). In addition, the quality of smoked mackerel from frozen-thawed fillets (9 months at -25 ± 1.8°C) was compared to that of fresh-smoked fillets to evaluate the possibility of the industry being able to provide smoked fillets throughout the year, despite the short fishing season. Brining and hot-smoking reduced total viable counts and inactivated Listeria monocytogenes. Hot-smoking positively affected the sensory attributes of the fillets and sensory quality was largely maintained for at least 21 days of chilled storage. Although slightly lower sensory and texture scores were obtained for frozen-thawed smoked fillets, they remained within acceptable limits throughout the period of cold storage. The shelf-life of smoked Atlantic mackerel deep-skinned fillets stored at 1°C is, therefore, assessed to be at least 21 days. Well-fed Atlantic mackerel is suitable for developing high-quality and stable smoked fillet products from both fresh and frozen-thawed raw materials.

Pantanal yacare (Caiman yacare) tail fillets subjected to traditional hot smoking and liquid smoke

BACKGROUND

The present study aimed to evaluate the effects of hot smoking and liquid smoke on process yield, physicochemical properties, microbiological parameters, fatty acid profile, benzo(a)pyrene levels, and sensory profile of Pantanal yacare tail fillets. The fillets were subjected to two types of smoking processes: hot smoking and liquid smoke flavoring.

RESULTS

The process yield of liquid-smoked fillets was higher (69.8%) compared to hot-smoked fillets (58.0%). All fillets were with good microbiological quality and low benzo(a)pyrene levels and were well accepted by consumers. The hot-smoked fillets and the liquid-smoked fillets presented 456.2 and 589.7 g kg^-1 moisture, 262.3 and 263.7 g kg^-1 crude protein, 218 and 85 g kg^-1 total lipids, and 26.0 and 20.9 g kg^-1 ash, respectively. The major fatty acids identified in the smoked tail fillets were palmitic, stearic, oleic, and linoleic acids.

CONCLUSION

The liquid-smoked fillets had lower lipid content, and higher process yield because of lower losses; thus, they proved to be more advantageous and practical to obtain than the hot-smoked fillets. © 2022 Society of Chemical Industry.

Investigations of the Polycyclic Aromatic Hydrocarbon and Elemental Profile of Smoked Fish

Fish are vulnerable to environmental pollutants such as polycyclic aromatic hydrocarbon and heavy metals. As one of the most commonly applied processing methods, the smoking of different species has been applied globally. Hence, this study aims to investigate the smoking process on the polycyclic aromatic hydrocarbon and elemental accumulation of the five different species (rainbow trout, Atlantic bonito, horse mackerel, sea bass, and Atlantic bluefin tuna) which are commonly processed and traded in the smoked fish industry. The processing yield, water holding capacity, and pH were also investigated. The results revealed that the proximal differences among fish species influence the water holding capacity, processing yield, and pH which are very important for process sustainability and the quality of the end product. The main finding was the proximal composition impact on the accumulation of both PAHs and heavy metals at different levels. While all of the tested samples were below the maximum permissible limit, some of the heavy metals, especially toxic elements, were found above the acceptable limit. Horse mackerel is determined to be the species most vulnerable to PAHs and heavy metal accumulation.

Use of Food Spoilage and Safety Predictor for an “A Priori” Modeling of the Growth of Lactic Acid Bacteria in Fermented Smoked Fish Products

Fermentation is one of the oldest methods to assure the safety and quality of foods, and to prolong their shelf life. However, a successful fermentation relies on the correct kinetics depending on some factors (i.e., ingredients, preservatives, temperature, inoculum of starter cultures). Predictive microbiology is a precious tool in modern food safety and quality management; based on the product characteristics and the conditions occurring in food processing, the inactivation of or increase in microbial populations could be accurately predicted as a function of the relevant intrinsic or extrinsic variables. The main aim of this study was the optimization of the formula of a smoked fermented fish product using predictive modeling tools (tertiary and secondary models) in order to define the role of each factor involved in the formulation and assure a correct course of fermentation. Product optimization was conducted through the software Food Spoilage and Safety Predictor (FSSP), by modeling the growth of lactic acid bacteria (LAB) as a function of some key parameters such as temperature, pH, salt, liquid smoke, carbon dioxide, and nitrites. The variables were combined through a fractional design of experiments (DoE) (3^k-p), and the outputs of the software, i.e., the maximal growth rate (μ_max) and the time to attain the critical threshold (t_crit), were modeled through a multiple regression procedure. The simulation, through FSSP and DoE, showed that liquid smoke is the most critical factor affecting fermentation, followed by temperature and salt. Concerning temperature, fermentation at 20–25 °C is advisable, although a low fermentation temperature is also possible. Other parameters are not significant.

Steam precooking, an effective pretreatment to reduce contamination with polycyclic aromatic hydrocarbons in traditionally smoked shrimp

Abstract

Traditionally smoked shrimps are highly contaminated with carcinogenic polycyclic aromatic hydrocarbons (PAHs). The effect of precooking methods such as boiling (7 and 15 min) and steaming (15 and 20 min) on shrimp smoking effectiveness was investigated through smoking duration and the change of moisture, protein content, and PAHs contamination. The consumer's perception of derived shrimps was highlighted by acceptability and Just-About-Right test using 7-point hedonic and 3-point scale respectively. Both precooking methods didn't affect the shrimp protein content while steaming reduced significantly moisture content. All the precooking methods reduced significantly the smoking duration with the lowest values for steaming. Smoking with or free from precooking increased significantly PAHs content of shrimp. Although, the PAHs trends showed similar pattern for both precooking methods, steaming during 20 min before smoking enables to have the shrimp with Benzo[a]pyrene (BaP) and sum of benzo[b]fluoranthene, benzo[a]anthracene, chrysene and BAP (PAH4) contents lower to the safety limit recommended by the European regulation. Irrespective of consumption forms, main sensory attributes of smoked steamed shrimps were scored as Just-About-Right by most consumers (65 to 88%). Steam precooking (20 min) is the better way for upgrading the shrimp safety with expected liking of consumers.

Graphical abstract

Structural Transformation and Creativity Induced by Biological Agents during Fermentation of Edible Nuts from Terminalia catappa

Terminalia catappa L. (tropical almond) is a nutritious fruit found mainly in the tropics. This study is aimed to establish the naturally biotransformed molecules and identify the probiotic agents facilitating the fermentation. The aqueous extracts from both the unfermented and fermented T. catappa nuts were subjected to gas chromatography/mass spectrometry (GC/MS) analysis. Syringol (6.03%), glutamine (1.71%), methyl laurate (1.79%), methyl palmitate (1.53%), palmitic acid (5.20%), palmitoleic acid (2.80%), and methyl oleate (2.97%) were detected in the unfermented nuts of the T. catappa. Additionally, two of these natural compounds (palmitic acid (4.19%) and palmitoleic acid (1.48%)) survived the fermentation process to emerge in the fermented seeds. The other natural compounds were biotransformed into 2,3-butanediol (1.81%), butyric acid (16.20%), propane-1,3-diol (19.66%), neoheptanol (2.89%), 2-piperidinone (6.63%), palmitoleic acid (1.18%), formamide, n-(p-hydroxyphenethyl)- (2.80%), and cis-vaccenic acid (1.69%) that newly emerged in the fermented seeds. The phytochemical compounds are likely carbon sources for the organisms facilitating the biotransformed molecules and product production. Four (4) potential probiotic bacteria strains, namely, Probt B1a, Probt B2a, Probt B4a, and Probt B4b, were isolated from the fermented nut. Enterococcus faecum, and Enterococcus faecalis were the organisms identified as driving the fermentation of the seeds. All strains were gram-positive, catalase-negative, and non-hemolytic, which suggests their harmless nature. N-(p-hydroxyphenethyl)-) was associated with fermentation for the first time, and neoheptanol was discovered as the main alcoholic molecule formed during the fermentation of the seeds. This fermentation is a handy tool for bio-transforming compounds in raw food sources into compounds with nutritious and therapeutic potentials.

Effect of processing smoked salmon on contaminant contents

The influence of the type of smoking process (natural/liquid; hot/cold) and salt (NaCl or KCl) on the levels of polybrominated diphenyl ethers (PBDEs) and polycyclic aromatic hydrocarbons (PAHs) in smoked salmon was evaluated. One parent compound - BDE 47 - and two methoxylated forms - 2'-MeO-BDE-68 and 6-MeO-BDE-47 - were detected in all the samples. Among the 14 PAHs analysed, naphthalene was the most abundant followed by phenanthrene and fluorene. Only smoked salmon treated with NaCl presented quantifiable levels of chrysene and benzo[b]fluoranthene. Among the four smoking processes evaluated, natural smoke led to higher levels of PAHs. Risk characterization tools, such as hazard index (HI) and incremental lifetime cancer risk (ILCR), showed that the risk of both PBDEs and PAHs to human health through the consumption of smoked salmon was very low.

Alternative Routes for the Production of Natural 4-Vinylguaiacol from Sugar Beet Fiber Using Basidiomycetous Enzymes

Traditional smoking generates not only the impact flavor compound 4-vinylguaiacol, but concurrently many unwanted and potent toxic compounds such as polycyclic aromatic hydrocarbons. Enzyme technology provides a solution without any side-product formation. A feruloyl esterase from Rhizoctonia solani (RspCAE) liberated ferulic acid from low-priced sugar beet fiber. Decarboxylation of ferulic acid to 4-vinylguaiacol was achieved by a second enzyme from Schizophyllum commune (ScoFAD). Both enzymes were covalently immobilized on agarose to enable reusability in a fixed-bed approach. The two enzyme cascades showed high conversion rates with yields of 0.8 and 0.95, respectively, and retained activity for nearly 80 h of continuous operation. The overall productivity of the model process with bed volumes of 300 µL and a substrate flow rate of 0.25 mL min−1 was 3.98 mg 4-vinylguaiacol per hour. A cold online solid phase extraction using XAD4 was integrated into the bioprocess and provided high recovery rates during multiple elution steps. Attempting to facilitate the bioprocess, a fused gene coding for the two enzymes and a set of different linker lengths and properties was constructed and introduced into Komagataella phaffii. Longer and rigid linkers resulted in higher activity of the fusion protein with a maximum of 67 U L−1.

An Approach to the Consumption of Smoked Paprika in Spain and its Impact on the Intake of Polycyclic Aromatic Hydrocarbons

"Pimentón de La Vera" smoked paprika is a traditional kind of smoked paprika, the production of which is regulated by a protected designation of origin. The traditional drying/smoking process provides the "Pimentón de La Vera" smoked paprika with a peculiar flavour which has gained acceptance in multiple markets. However, this process also gives rise to non-desirable substances, such as polycyclic aromatic hydrocarbons (PAHs). This paper attempts to ascertain the consumption levels of smoked paprika per person in Spain in order to establish the intake of PAHs derived from this food spice. With this purpose in mind, a research study was carried out using questionnaires in three different smoked paprika consumption scenarios: food companies, households and restaurants. The results from this research proved that the average consumption of smoked paprika per person per year in Spain is 139 g. Overall, the intake of PAHs derived from smoked paprika was proven to represent a negligible fraction of the total intake, with this ingredient being far behind the PAH contribution represented by other food products. These results could help consolidate the smoked paprika production sector by providing evidence of the scarce contribution of smoked paprika to PAH intake and justifying the traditional production with smoke drying, which is the differentiating quality trait of this spice.

Generation of 4-vinylguaiacol through a novel high-affinity ferulic acid decarboxylase to obtain smoke flavours without carcinogenic contaminants

Traditional smoke flavours bear the risk of containing a multitude of contaminating carcinogenic side-products. Enzymatic decarboxylation of ferulic acid released from agro-industrial side-streams by ferulic acid esterases (FAE) enables the sustainable generation of pure, food grade 4-vinylguaiacol (4-VG), the impact compound of smoke flavour. The first basidiomycetous ferulic acid decarboxylase (FAD) was isolated from Schizophyllum commune (ScoFAD) and heterologously produced by Komagataella phaffii. It showed a molecular mass of 21 kDa, catalytic optima at pH 5.5 and 35°C, and a sequence identity of 63.6% to its next relative, a FAD from the ascomycete Cordyceps farinosa. The ScoFAD exhibited a high affinity to its only known substrate ferulic acid (FA) of 0.16 mmol L^-1 and a turnover number of 750 s^-1. The resulting catalytic efficiency k_cat K_M^-1 of 4,779 L s^-1 mmol^-1 exceeded the next best known enzyme by more than a factor of 50. Immobilised on AminoLink Plus Agarose, ScoFAD maintained its activity for several days. The combination with FAEs and agro-industrial side-streams paves the way for a new generation of sustainable, clean, and safe smoke flavours.

Comparison of Polyaromatic Hydrocarbon Residue Concentrations in Clarias gariepinus Smoked with Traditional and Mechanical Kilns

BACKGROUND

Wood, a common fueling material for fish smoking in Nigeria, contains polycyclic aromatic hydrocarbons (PAHs) which have been found to be carcinogenic and pose a human health hazard.

OBJECTIVES

The present study investigated the interactions and effects of kiln types on levels of PAHs in smoked fish.

METHODS

Twenty fresh samples of Clarias gariepinus with an average size of 800 g were eviscerated, washed and salted for smoking. Sixteen (16) of the fish were randomly and equally allotted to each of the two kilns (treatments) and replicated three times in a completely randomized design. Each kiln was loaded and heated up with hard wood charcoal and the effects were evaluated on the resulting smoked fish. The remaining four fish samples were kept under refrigeration (controls). Samples of the smoke-dried fish from each kiln were homogenized using a porcelain mortar and pestle, sieved through a 250-μm2 sieve, and packaged in labeled airtight containers prior to extraction. Pure extracts from the samples were subjected to gas chromatography.

RESULTS

The results showed that the PAH concentration in non-smoked catfish was 1.0 mg/kg, the PAH concentration in fish samples smoked with a traditional kiln was 2.0 mg/kg, and no PAHs were detected in samples smoked with a mechanical kiln.

CONCLUSIONS

The level of PAH contamination of smoked fish is dependent on the type of kiln used, as demonstrated by the differences between fished smoked with traditional and mechanical kilns in the present study.

COMPETING INTERESTS

The authors declare no competing financial interests.

Effects of Smoking Temperature, Smoking Time, and Type of Wood Sawdust on Polycyclic Aromatic Hydrocarbon Accumulation Levels in Directly Smoked Pork Sausages

Smoking is an excellent food preservation method but also a source of contamination of foodstuffs with carcinogenic polycyclic aromatic hydrocarbons (PAHs). Herein we investigated the influence of smoking temperature, smoking time, and type of wood sawdust used as smoke source on PAH levels attained through controlled smoking of pork sausages. Four PAHs (benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[a]pyrene) were monitored, as required by European Commission Regulation 835/2011. PAH concentrations increased continuously both with higher temperatures (55-95 °C) and with longer smoking periods (2-9 h), although the level of benzo[a]pyrene exhibited a tendency to plateau after 6 h. Among seven types of hardwoods tested, plum, alder, and birch yielded PAH concentrations considerably higher than that of commonly used beech, and oak showed similar levels to beech while apple and, to a lesser extent, walnut caused lower levels of sausage contamination. These findings could guide the establishment of good practices in the smoked meat industry.

Improvement of Sensorial, Physicochemical, Microbiological, Nutritional and Fatty Acid Attributes and Shelf Life Extension of Hot Smoked Half-Dried Pacific Saury (Cololabis saira)

Half-dried Pacific saury of Cololabis saira (HDPS) is a fatty fish of high nutritional value with remarkable consumer interest in the Asia Pacific region, however, it undergoes various deteriorative changes associated with browning, bacterial contamination, oxidation, and decreased sensory attributes while marketed in various processed forms. To withstand these complications, research aimed to investigate the hot smoking technology to improve physicochemical, microbiological, and sensory attributes of HDPS with prolonged shelf life in storage conditions. The HDPS fillets were processed with hot smoking (70 °C) using various sawdust materials of Apple, Chestnut, Oak, Cherry, and Walnut, wherein the smoke time was set at different time points of 0, 20, 25, and 30 min. The results indicated that 25 min of smoking time with the selective Oak sawdust showed better sensorial characteristics, physicochemical properties, and microbiological qualities. Moreover, HDPS possessed higher nutritional value and valuable functional fatty acids, particularly docosahexaenoic acid and eicosapentaenoic acid, having a storage ability of up to 30 days at 10 °C. The processed HDPS offered a reduced level of Trimethylamine-N-oxide and Benzo[a]pyrene contents, indicating the acceptable and safe for human consumption. Therefore, HDPS with hot smoking could likely be a promising technique for preserving the premium quality of the product by providing desired characteristics of health and nutrition to end-point consumers.

Analysis of Polycyclic Aromatic Hydrocarbons in Heregovački pršut-Traditionally Smoked Prosciutto

Hercegovački pršut as a traditional dry-cured smoked ham (prosciutto) produced by using an open fire that can be potentially contaminated with polycyclic aromatic hydrocarbons (PAHs) and can pose a health risk for consumers. The aim of this research was to identify the types and concentrations of 16 PAHs in 34 samples of traditionally smoked prosciutto. Out of 16 investigated PAHs, identified in the EPA (Environmental Protection Agency) list of priority pollutants, 14 compounds were detected. Average levels of cancerogenic benzo[a]pyrene (BaP) and PAH4 (benzo[a]anthracene (BaA), benzo[b]fluoranthene (BbF), chrysene (Chry), and benzo[a]pyrene (BaP)) ranged from <LOQ (level of quantification) to 5.08 μg/kg and 0.45 μg/kg to 22.67 μg/kg. Two analyzed samples exceeded currently prescribed values according to the Bosnia and Herzegovina legislation for BaP concentrations and one sample for PAH4 content. PAH16 concentrations were on average between 2.92 μg/kg and 87.6 μg/kg. The highest PAH concentrations were found in samples from the Herzegovina-Neretva canton. The results of the research highlight the importance of standardizing smoking procedures and manufacturing practice, in the production of Hercegovački pršut, in order to reduce the PAH content.

Review of polycyclic aromatic hydrocarbons (PAHs) in fish and fisheries products; a Sri Lankan perspective

Polycyclic aromatic hydrocarbons (PAHs) are emerging as important contaminants in smoked and smoke-dried fish and fish products. The smoking techniques and different parameters contribute to the PAH load in smoked fish. This review paper provides insight into the PAHs and their sources and pathways to fish, effects on human health, smoking parameters and PAHs, regulations, available information, gaps in present knowledge, and future prospects in smoked fish from Sri Lanka. Based on the very few available research reports on PAH levels in smoked fish from Sri Lanka, it is concluded that the smoked fish are not safe for human consumption according to the regulation limits published by the European Union (EU). It is therefore important to implement proper guidelines and produce a safe product to ensure that hazards are managed as appropriate Hazard Analysis and Critical Control Points (HACCP). Graphical abstract.

Polycyclic aromatic hydrocarbons in traditionally smoked Slavonska kobasica

The traditional smoking procedure, which is the use of open fire, can lead to the formation of PAHs in sausages. The aim of this paper was to assess the types and concentrations of 16 PAHs in 30 samples of Slavonska kobasica, a traditional smoked sausage. In general, some samples showed high values of anthracene and acenaphthylene. In one sample, acenaphthylene reached the value of 1050 µg/kg and in another 1491 µg/kg anthracene was measured. Cancerogenic benzo(a)pyrene content was little above the maximum limit of 5 µg/kg in four samples, but mainly remained below the limit of quantification. PAH4 (i.c. benzo(a)anthracene, chrysene, benzo(b)fluoranthene and benzo(a)pyrene) were above the maximum limit of 30 µg/kg in three samples. Generally, it can be noted from the results that samples with high PAH4 and benzo(a)pyrene concentrations also have high PAH16 concentrations.

Review on Natural Preservatives for Extending Fish Shelf Life

Fish is extremely perishable as a result of rapid microbial growth naturally present in fish or from contamination. Synthetic preservatives are widely used in fish storage to extend shelf life and maintain quality and safety. However, consumer preferences for natural preservatives and concerns about the safety of synthetic preservatives have prompted the food industry to search natural preservatives. Natural preservatives from microorganisms, plants, and animals have been shown potential in replacing the chemical antimicrobials. Bacteriocins and organic acids from bacteria showed good antimicrobial activities against spoilage bacteria. Plant-derived antimicrobials could prolong fish shelf life and decrease lipid oxidation. Animal-derived antimicrobials also have good antimicrobial activities; however, their allergen risk should be paid attention. Moreover, some algae and mushroom species can also provide a potential source of new natural preservatives. Obviously, the natural preservatives could perform better in fish storage by combining with other hurdles such as non-thermal sterilization processing, modified atmosphere packaging, edible films and coatings.