Parvalbumin in fish skin-derived gelatin: is there a risk for fish allergic consumers?

The major allergen parvalbumin was purified from cod muscle tissues, and polyclonal antibodies were raised towards it. The antibodies were tested for specificity and an enzyme-linked immunosorbent assay (ELISA) was developed using these antibodies. The ELISA was applied to measure parvalbumin in cod skin, the starting material for fish gelatin made from deep sea, wild fish. The ELISA was sufficiently sensitive (LLOQ?=?0.8?ng?ml^?1 in extracts, corresponding to 0.02?µg of parvalbumin per g of tissue), and did not cross-react with common food constituents. Fish gelatin, wine and beer, matrices for the potential use of this ELISA, did not cause disturbance of the assay performance. The data show that the parvalbumin content in cod muscle tissue is 6.25?mg?g^?1, while the skins contained considerably less, 0.4?mg?g^?1. Washing of the skins, a common industrial procedure during the manufacturing of fish gelatin, reduced the level of parvalbumin about 1000-fold to 0.5?µg?g^?1, or 0.5?ppm. From 95 commercial lots of fish gelatin it is shown that 73 are below 0.02?µg?g^?1 parvalbumin. From the other 22 lots, the one with the highest concentration contained 0.15?µg?g^?1 of parvalbumin. These levels are generally assumed to be safe for fish-allergic individuals.     

Canthaxanthin in aquafeed applications: is there any risk?

The carotenoid pigment ‘canthaxanthin’ has been used in aquafeed for many years in order to impart the desired flesh colour in farmed salmonids. A side effect of extreme over-dosage of this carotenoid is the deposition of minute crystals in the eye, a fact leading to adverse media attention for canthaxanthin in the past, and some pressure to limit its use aquafeeds. A real appraisal of the possible amount of canthaxanthin ingested by humans through the consumption of notable quantities of highly pigmented salmon, reveals that it is extremely unlikely that consumers could be exposed to sufficient canthaxanthin to attain the established ADI for this pigment. Additionally, the ADI is 10 times lower than the reported no-effect level (NOEL) for canthaxanthin. Therefore, canthaxanthin is a safe source of carotenoids for salmonid feeds.     

Polyphenols in chocolate: is there a contribution to human health?

Recently, polyphenols have gained much more attention, owing to their antioxidant capacity (free radical scavenging and metal chelating) and their possible beneficial implications in human health, such as in the treatment and prevention of cancer, cardiovascular disease, and other pathologies. Cocoa is rich in polyphenols particularly in catechins (flavan-3-ols) and procyanidins. Polyphenol contents of cocoa products such as dark chocolate, milk chocolate and cocoa powder have been published only recently. However, the data vary remarkably due to the quantity of cocoa liquor used in the recipe of the cocoa products but also due to the analytical procedure employed. For example, results obtained by a colourimetric method were 5–7 times higher for the same type of product than results obtained by high performance liquid chromatography (HPLC). In 1994, the per head consumption of chocolate and chocolate confectionery in the European Union ranged from 1.3 kg/year in Portugal to 8.8 kg/year in Germany. In general, consumers in the Northern countries consume on average more than people in the South. Thus, chocolate can be seen as a relevant source for phenolic antioxidants for some European population. However, this alone does not imply, that chocolate could be beneficial to human health. Some epidemiological evidence suggests a beneficial effect to human health by following a polyphenol-rich diet, namely rich in fruits and vegetables and to a less obvious extent an intake of tea and wine having a similar polyphenol composition as cocoa. In many experiments cellular targets have been identified and molecular mechanisms of disease prevention proposed, in particular for the prevention of cancer and cardiovascular diseases as well as for alleviating the response to inflammation reactions. However, it has to be demonstrated, whether polyphenols exert these effects in vivo. One pre-requisite is that the polyphenols are absorbed from the diet. For monomeric flavonoids such as the catechins, there is increasing evidence for their absorption. For complex phenols and tannins (procyanidins) these questions have to be addressed for the future. Some indication for the absorption of procyanidins derive from studies with the human colon cancer cell line Caco-2, believed to be a valuable model for passive intestinal absorption as proposed for polyphenols. However, it has to be clarified which concentration is effective and what concentrations can be expected from food intake. Another open question is related to polyphenol metabolism. For example, much effort has been invested to show antioxidative effects of free unbound polyphenols, especially of catechins and the flavonol quercetin. However, only a very small part can be found in plasma in the free form but conjugated or even metabolised to several phenolic acids and other ring scission products. From the papers reviewed, it is as yet to early to give an answer to the question, whether chocolate and/or other sources rich in catechins and procyanidins are beneficial to human health. Even though some data are promising and justify further research in the field, it has to be shown in future, whether the intake of these functional compounds and/or their sources is related to measurable effects on human health and/or the development of diseases.     

Is there a future for antioxidants in atherogenesis?

Antioxidants, preferentially those of dietary origin, have for a long time been considered to help against diseases that are presumably aggravated by oxidative stress, such as cardiovascular diseases, cancer, and neurodegenerative disorders. The outcome of clinical trials undertaken to corroborate this hypothesis, however, remained largely inconclusive. Evidence is now emerging that some dietary "antioxidants" influence signaling pathways and the expression of genes relevant in atherosclerosis by mechanisms other than antioxidative ones. By concrete examples we show that (1) vitamin E has gene regulatory functions which might be more important than acting as an antioxidant in vivo, (2) selenium itself is not an antioxidant at all, and even not in general when incorporated into glutathione peroxidases, and (3) a moderate oxidative stress is beneficial rather than detrimental since it can induce defense mechanisms counteracting xenobiotic and oxidative stress. Thus, there is only a future for antioxidants in the prevention of any disease if their real mechanism of action is considered and suitable read-outs and biomarkers are established.     

Iron deficiency – is there a role for the food industry?

Iron deficiency is one of the most common nutritional deficiencies worldwide, in both developing and developed regions. Although the aetiology of iron deficiency and resultant anaemia may be multifaceted, inadequate iron intakes, poor iron absorption and disease status may all be underlying causes. Whilst nutrition and supplement interventions may go some way towards improving iron status in ‘at‐risk’ populations, their efficacy can be questioned. New approaches, including food‐based strategies, may be an alternative means of improving the iron status and health of the public sectors. Economically, food‐based approaches may also be more cost‐effective than iron supplements. This paper aims to discuss how the food industry may play an important role in improving the iron status of public sectors, helping to prevent iron deficiency and need for tablet‐based iron supplements.     

State of the art in the validation of screening methods for the control of antibiotic residues: is there a need for further development?

ABSTRACT

Screening methods are used as a first-line approach to detect the presence of antibiotic residues in food of animal origin. The validation process guarantees that the method is fit-for-purpose, suited to regulatory requirements, and provides evidence of its performance. This article is focused on intra-laboratory validation. The first step in validation is characterisation of performance, and the second step is the validation itself with regard to pre-established criteria. The validation approaches can be absolute (a single method) or relative (comparison of methods), overall (combination of several characteristics in one) or criterion-by-criterion. Various approaches to validation, in the form of regulations, guidelines or standards, are presented and discussed to draw conclusions on their potential application for different residue screening methods, and to determine whether or not they reach the same conclusions. The approach by comparison of methods is not suitable for screening methods for antibiotic residues. The overall approaches, such as probability of detection (POD) and accuracy profile, are increasingly used in other fields of application. They may be of interest for screening methods for antibiotic residues. Finally, the criterion-by-criterion approach (Decision 2002/657/EC and of European guideline for the validation of screening methods), usually applied to the screening methods for antibiotic residues, introduced a major characteristic and an improvement in the validation, i.e. the detection capability (CCβ).

In conclusion, screening methods are constantly evolving, thanks to the development of new biosensors or liquid chromatography coupled to tandem-mass spectrometry (LC-MS/MS) methods. There have been clear changes in validation approaches these last 20 years. Continued progress is required and perspectives for future development of guidelines, regulations and standards for validation are presented here.     

Modelling bacterial growth in quantitative microbiological risk assessment: is it possible?

Quantitative microbiological risk assessment (QMRA), predictive modelling and HACCP may be used as tools to increase food safety and can be integrated fruitfully for many purposes. However, when QMRA is applied for public health issues like the evaluation of the status of public health, existing predictive models may not be suited to model bacterial growth. In this context, precise quantification of risks is more important than in the context of food manufacturing alone. In this paper, the modular process risk model (MPRM) is briefly introduced as a QMRA modelling framework. This framework can be used to model the transmission of pathogens through any food pathway, by assigning one of six basic processes (modules) to each of the processing steps. Bacterial growth is one of these basic processes. For QMRA, models of bacterial growth need to be expressed in terms of probability, for example to predict the probability that a critical concentration is reached within a certain amount of time. In contrast, available predictive models are developed and validated to produce point estimates of population sizes and therefore do not fit with this requirement. Recent experience from a European risk assessment project is discussed to illustrate some of the problems that may arise when predictive growth models are used in QMRA. It is suggested that a new type of predictive models needs to be developed that incorporates modelling of variability and uncertainty in growth.     

Horizontal gene transfer in the gut: Is it a risk?

The human gastro-intestinal microbiota involves the highest concentration of microorganisms in the human body and contains both probiotic and pathogenic bacteria. The co-presence of these different bacteria may lead to the occurrence of the so-called horizontal gene transfer (HGT) between these microorganisms. This phenomenon has been shown to allow the transfer of genes encoding virulence traits and antimicrobial drug resistance from pathogenic bacteria to other non-pathogenic strains, which highlighted its significance to human health. It could be envisaged that HGT may occur between pathogenic and probiotic bacteria in the gut, where pathogens could receive genetic elements from probiotics that enhance the pathogen’s colonization in the gut. HGT may also allow for the acquisition of virulence genes by probiotics from neighboring gut pathogens. Pertinent literature on HGT events within gut microbiota is controversial and the present paper aims to critically address this aspect. In light of an increased production of probiotics-containing foods, addressing HGT would be a vital act to ensure food safety.     

Lessening of high-pressure-induced changes in Atlantic salmon muscle by the combined use of a fish gelatin–lignin film

Salmon muscle is considerably affected by cooking with the resulting loss of its appealing red colour. The combined use of high pressure with fish gelatin–lignin film is proposed as an alternative to the more aggressive thermal processing procedures, with the aim of improving the appearance and overall quality of salmon fillets in ready-to-eat or semi-prepared dishes. The effects of high pressure processing (300 MPa, 10 min, 5 °C or 40 °C) and conventional heating (90 °C, 10 min) were evaluated in terms of colour changes, protein denaturation, as well as protein and lipid oxidation, by comparison with raw muscle. The stability of the processed products was assessed by monitoring changes in microbial growth and total volatile basic nitrogen and thiobarbituric acid reactive substances during 23 days of chilled storage. Fourier transform infrared spectroscopy (FTIR), apparent viscosity and dynamic oscillatory studies revealed notable differences in the overall degree and nature of protein aggregation between high pressure and heating treatments, especially when performed at 5 °C instead of 40 °C. SDS–PAGE of the protein fraction solubilised in 0.8 M NaCl showed MHC and α-actinin to be the main myofibrillar proteins denatured by high pressure processing at 40 °C, while actin was more denatured when pressurised at 5 °C. The film attenuated colour changes associated with high pressure treatment, especially at 5 °C, where redness was more preserved without jeopardising the appearance of a ready-to-eat product. High pressure processing at 5 °C in combination with gelatin–lignin film was found to improve protein quality of salmon fillets. The film reduced the levels of carbonyl groups formed immediately after processing, and prevented lipid oxidation from taking place at advanced stages of chilled storage. However, the effect on microbial growth was negligible, since total counts were similar for muscle with or without the film.     

Brominated and fluorinated organic pollutants in the breast milk of first-time Irish mothers: is there a relationship to levels in food?

Brominated flame retardants – polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs), hexabromocyclododecane (HBCD) and others – have been measured in 11 pooled breast milk samples from 109 first-time mothers in Ireland. Additionally, the study has measured levels of polybrominated dibenzo-p-dioxins and furans (PBDD/Fs), mixed halogenated dioxins (PXCC/Fs) and biphenyls (PXBs), polychlorinated naphthalenes (PCNs) and perfluoroalkylated substances (PFAS) in these samples. The mean sum of 19 PBDEs including BDE-209 was 4.85 ng g^?1 fat, which is comparable with that found in other European countries. BDE-47, BDE-153, BDE-209, BDE-99 and BDE-100 were found at the highest concentrations. The only PBBs detected consistently were BB-77, BB-126 and BB-153, with highest concentrations being found for BB-153 (mean = 0.13 ng g^?1 fat). The mean sum of HBCD enantiomers was 3.52 ng g^?1 fat, with α-HBCD representing over 70% of the total. Of the other brominated flame retardants – tetrabromobisphenol-A (TBBP-A), hexabromobenzene (HBB), decabromodiphenylethane (DBDPE) and bis(2,4,6-tribromophenoxyethane) (BTBPE) – examined, only TBBP-A was detected above the limit of detection (LOD), in two of the 11 pools analysed. All measured PBDF congeners were observed (at 0.02–0.91 pg g^?1 fat), but 2,3,7,8-tetrabromo-dibenzodioxin (TeBDD) was the only PBDD detected, with a mean concentration of 0.09 pg g^?1 fat. The occurrence of the mixed chlorinated/brominated dibenzodioxins, dibenzofurans and biphenyls, 2-B-3,7,8-CDD, 2,3-B-7,8-CDF, 4-B-2,3,7,8-CDF, PXB 105, PXB 118, PXB 126 and PCB 156 in breast milk in the current study may indicate that levels of these contaminants are increasing in the environment. Polychlorinated naphthalenes were detected in all samples, but not perfluorooctane sulfonate (PFOS) and other PFAS. The pattern of occurrence of these brominated and fluorinated persistent organic pollutants (POPs) in Irish breast milk shows a general relationship to their occurrence in food, as reported in a number of surveillance studies carried out by the Food Safety Authority of Ireland.     

Quantitative risk–benefit analysis of fish consumption for women of child-bearing age in Hong Kong

Maternal fish consumption is associated with both risks from methylmercury (MeHg) and beneficial effects from omega-3 fatty acids to the developing foetal brain. This paper assessed the dietary exposure to MeHg of women of child-bearing age (20–49 years) in Hong Kong, and conducted risk–benefit analysis in terms of the effects in children’s intelligent quotient (IQ) based on local data and the quantitative method derived by the expert consultation of FAO/WHO. Results showed that average and high consumers consume 450 and 1500 g of fish (including seafood) per week, respectively. About 11% of women of child-bearing age had a dietary exposure to MeHg exceeding the PTWI of 1.6 µg kg^–1 bw. In pregnant women MeHg intake may pose health risks to the developing foetuses. For average consumers, eating any of the 19 types of the most commonly consumed fish and seafood during pregnancy would result in 0.79–5.7 IQ points gain by their children. For high consumers, if they only ate tuna during pregnancy, it would cause 2.3 IQ points reduction in their children. The results indicated that for pregnant women the benefit outweighed the risk associated with eating fish if they consume different varieties of fish in moderation.     

Study of gelatin renaturation in aqueous solution by AFlFFF–MALS: Influence of a thermal pre-treatment applied on gelatin

Asymmetrical Flow Field-Flow Fractionation coupled to Multi-Angle Light Scattering has been applied to study and understand the renaturation phenomenon of gelatin in dilute aqueous solutions. Renaturation behaviour has been studied on a native gelatin powder and compared to the same gelatin, pre-heated at 75 °C. An increase of molar mass, due to gelatin chains association at room temperature was observed for native gelatin. AFlFFF–MALS analysis allowed to follow α, β, γ chains association and the occurrence of other fractions with high molar mass. This process was absent in pre-heated gelatin which suggested that pre-heating process could lead to interactions between gelatin chains which limited renaturation process in aqueous solutions. For pre-heated gelatin samples, the average initial molar mass was higher and hardly changed during incubation of a dilute solution.     

Bioconcentration of organic chemicals: is a solid-phase microextraction fiber a good surrogate for biota?

When organic chemicals are extracted from a water sample with solid-phase microextraction (SPME) fibers, the resulting concentrations in exposed fibers are proportional to the hydrophobicity of the compounds. This fiber accumulation is analogous to the bioconcentration of chemicals observed in aquatic organisms. The objective of this study was to investigate the prospect of measuring the total concentration in SPME fibers to estimate the total body residue in biota for the purpose of risk assessment. Using larvae of the midge, Chironomus riparius and disposable 15-microm poly(dimethylsiloxane) fibers, we studied the accumulation and accumulation kinetics of a number of narcotic compounds with a range of log K(ow) between 3 and 6. The fibers, which have a larger surface area-to-volume ratio, had consistently higher uptake and elimination rate constants (k1 and k2, respectively) than midge larvae and accumulated the chemicals 5 times faster. Comparison of the relationships of the partition coefficients K(PDMS-water) and K(midge-water) (lipid-normalized) to log K(ow) for all compounds yielded a factor of 28 for translating fiber concentrations to biota concentrations. This factor can be used to estimate internal concentrations in biota for compounds structurally similar to the compounds in this study. The exact chemical domain to which this factor can be applied needs to be defined in future research.