Process-induced undesirable compounds: Chances of non-thermal approaches

DNA Alkylation Damage by Nitrosamines and Relevant DNA Repair Pathways

Nitrosamines occur widespread in food, drinking water, cosmetics, as well as tobacco smoke and can arise endogenously. More recently, nitrosamines have been detected as impurities in various drugs. This is of particular concern as nitrosamines are alkylating agents that are genotoxic and carcinogenic. We first summarize the current knowledge on the different sources and chemical nature of alkylating agents with a focus on relevant nitrosamines. Subsequently, we present the major DNA alkylation adducts induced by nitrosamines upon their metabolic activation by CYP450 monooxygenases. We then describe the DNA repair pathways engaged by the various DNA alkylation adducts, which include base excision repair, direct damage reversal by MGMT and ALKBH, as well as nucleotide excision repair. Their roles in the protection against the genotoxic and carcinogenic effects of nitrosamines are highlighted. Finally, we address DNA translesion synthesis as a DNA damage tolerance mechanism relevant to DNA alkylation adducts.

The Impact of a Pulsed Light Stream on the Quality and Durability of the Cold-Stored Longissimus Dorsal Muscle of Pigs

The purpose of this study was to investigate the effect of pulsed light application (exposure to a pulsed light beam (PL) of 400 Hz for a period of 60 s, with an energy dose of 600 mW and wavelengths of 660 and 405 nm) on the physicochemical, technological, and sensory properties, as well as the nutritional value and shelf life of cold-storage pig longissimus dorsi muscle. Each muscle was divided into six parts, three of which were control samples, and the rest were exposed to pulsed light. The detailed laboratory tests of the meat were conducted 1, 7, and 10 days after slaughter. The meat was cold stored at +3 °C ± 0.5 °C. The study showed that the application of pulsed light has a favorable effect on lowering the TBARS index, oxidation-reduction potential, and water activity values. In addition, the application of PL had no statistically significant effect on the variation in the perception of selected sensory characteristics of meat. Furthermore, PL processing, as a low-energy-intensive method that can be environmentally friendly and thus have a large potential for implementation, is an innovative way to extend the shelf life, especially of raw meat, without a negative impact on its quality. This is of particular importance for food security (especially in the quantitative and qualitative aspects of food, but also in terms of food safety).

An integrated method for monitoring thermal processing temperature of pork based on Q-Exactive mass spectrometry and chemometrics

Meat heating endpoint temperature (EPT) is an important indicator to ensure the safety of cooked meat. Accurately determining the EPT of cooked meat and ready-to-eat meat products is an important strategy to ensure food safety. In this study, a comprehensive metabolic method based on UPLC-Q Exactive and chemometrics was developed to study the metabolites differences among pork roasted at different temperatures in order to select markers indicating EPT and discover new toxic heat-induced compounds. A two-step extraction method was applied to avoid the loss of metabolite information caused by sample preparation. Using chemometrics, the five compounds of creatine, creatinine, 2-amino-1-methyl-6-phenylimidazo (4,5-b) pyridine (PhIP), 2-methyl-6-amino-5-hydroxymethylpyrimidine (TMP) and compound with the m/z of 114.04316 were selected as markers, and four of them were further confirmed by chemical standards. It is worth noting that TMP was discovered in roasted pork for the first time. In addition, targeting studies aimed at quantifying the selected markers were conducted at different thermal processing temperatures. From the quantification results, it can be concluded that the heat temperature not exceed 180 °C is recommended to reduce the content of toxic compounds. This study has proved that the integration of UPLC-Q Exactive and chemometrics could provide an efficient method for the study of markers related to thermal process and new toxic heat-induced compounds.

Unconventional Methods of Preserving Meat Products and Their Impact on Health and the Environment

A dual objective of food storage is to retain nutritional value and safe consumption over time. As supply chains have globalized, food protection and preservation methods have advanced. However, increasing demands to cater for larger volumes and for more effective food storage call for new technologies. This paper examines promising meat preservation methods, including high pressure process, ultrasounds, pulsating electric and magnetic field, pulsed light and cold plasma. These methods not only make it possible to obtain meat and meat products with a longer shelf life, safer for health and without preservatives, but also are more environment-friendly in comparison with traditional methods. With the use of alternative methods, it is possible to obtain meat products that are microbiologically safer, whilst also high quality and free from chemical additives. Moreover, these new technologies are also more ecological, do not require large quantities of energy or water, and generate less waste.

Bio-protective potential of lactic acid bacteria: Effect of Lactobacillus sakei and Lactobacillus curvatus on changes of the microbial community in vacuum-packaged chilled beef

OBJECTIVE

This study was to determine the bacterial diversity and monitor the community dynamic changes during storage of vacuum-packaged sliced raw beef as affected by Lactobacillus sakei and Lactobacillus curvatus.

METHODS

L. sakei and L. curvatus were separately incubated in vacuumed-packaged raw beef as bio-protective cultures to inhibit the naturally contaminating microbial load. Dynamic changes of the microbial diversity of inoculated or non-inoculated (control) samples were monitored at 4°C for 0 to 38 days, using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE).

RESULTS

The DGGE profiles of DNA directly extracted from non-inoculated control samples highlighted the order of appearance of spoilage bacteria during storage, showing that Enterbacteriaceae and Pseudomonas fragi emerged early, then Brochothrix thermosphacta shared the dominant position, and finally, Pseudomonas putida showed up became predominant. Compared with control, the inoculation of either L. sakei or L. curvatus significantly lowered the complexity of microbial diversity and inhibited the growth of spoilage bacteria (p<0.05). Interestingly, we also found that the dominant position of L. curvatus was replaced by indigenous L. sakei after 13 d for L. curvatus-inoculated samples. Plate counts on selective agars further showed that inoculation with L. sakei or L. curvatus obviously reduced the viable counts of Enterbacteraceae, Pseudomonas spp. and B. thermosphacta during later storage (p< 0.05), with L. sakei exerting greater inhibitory effect. Inoculation with both bio-protective cultures also significantly decreased the total volatile basic nitrogen values of stored samples (p<0.05).

CONCLUSION

Taken together, the results proved the benefits of inoculation with lactic acid bacteria especially L. sakei as a potential way to inhibit growth of spoilage-related bacteria and improve the shelf life of vacuum-packaged raw beef.

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Zusammenfassung.In der Schweiz werden pro Tag im Schnitt 110 g Fleisch verzehrt, darunter 40 g verarbeitetes Fleisch. Ein hoher Verzehr besonders von verarbeitetem Fleisch wurde von der International Agency for Research on Cancer als krebserregend eingestuft, wobei die Evidenz vor allem auf dem Zusammenhang mit Dickdarmkrebs beruht. Als mögliche Mechanismen gelten eine hohe Aufnahme von Kochsalz (im Zusammenhang mit Magenkrebs), die Aufnahme sowie die endogene Bildung von N-Nitroso-Verbindungen (teilweise gefördert durch den hohen Gehalt von Hämeisen in rotem Fleisch) und die Bildung von polyzyklischen Kohlenwasserstoffen und heterozyklischen aromatischen Amine bei der Fleischzubereitung. Die Schweizerische Gesellschaft für Ernährung empfiehlt aus diesem Grund, lediglich 2–3 Portionen Fleisch und Fleischprodukte pro Woche zu verzehren.

Should we recommend reductions in saturated fat intake or in red/processed meat consumption? The SUN prospective cohort study

BACKGROUND & AIMS

While most studies have shown increased mortality associated with excessive red/processed meat consumption, the association of saturated fatty acids (SFA) intake with mortality is less homogeneous. We aimed to prospectively assess the association of both, meat consumption (red, processed, red + processed, and total) and SFA intake, with the risk of all-cause death.

METHODS

We assessed 18,540 participants of the SUN (Seguimiento Universidad de Navarra) cohort, followed-up for a mean of 9.5 years. A validated 136-item FFQ was administered at baseline. We used Cox models adjusted for potential confounders.

RESULTS

We observed 255 deaths during 176,916 person-years of follow-up. Age modified the association between meat consumption and all-cause mortality (p for interaction = 0.027, 0.075, and 0.013, for red, total, and processed meat, respectively). Among participants aged >45 years the fully-adjusted HRs (95% CIs) for one additional serving/d of red, total, and red + processed meat consumption were 1.47 (1.06, 2.04), 1.23 (1.05, 1.45), and 1.32 (1.05, 1.65), respectively, with significant linear trends (P for trend 0.022, 0.012, and 0.018, respectively). In these participants, SFA intake was non-significantly associated with mortality. However, isocaloric replacement of monounsaturated fat or carbohydrates by SFA resulted in significantly higher mortality risk. Likewise, replacing 100 g of vegetables, fruits & nuts or cereals by 100 g of red meat resulted in higher mortality risk. No association of meat consumption or SFA with all-cause mortality was observed in participants younger than 46 years.

CONCLUSIONS

Among highly educated persons, aged >45 years, a high consumption of red, total, and red + processed meat was related to increased all-cause mortality, compared with those with low consumption, whereas no significant associations were found for SFA intake. Dietary guidelines should specifically limit meat consumption and not relying only in limiting SFA intake.

Impact of DNA repair on the dose-response of colorectal cancer formation induced by dietary carcinogens

Colorectal cancer (CRC) is one of the most frequently diagnosed cancers, which is causally linked to dietary habits, notably the intake of processed and red meat. Processed and red meat contain dietary carcinogens, including heterocyclic aromatic amines (HCAs) and N-nitroso compounds (NOC). NOC are agents that induce various N-methylated DNA adducts and O⁶-methylguanine (O⁶-MeG), which are removed by base excision repair (BER) and O⁶-methylguanine-DNA methyltransferase (MGMT), respectively. HCAs such as the highly mutagenic 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) cause bulky DNA adducts, which are removed from DNA by nucleotide excision repair (NER). Both O⁶-MeG and HCA-induced DNA adducts are linked to the occurrence of KRAS and APC mutations in colorectal tumors of rodents and humans, thereby driving CRC initiation and progression. In this review, we focus on DNA repair pathways removing DNA lesions induced by NOC and HCA and assess their role in protecting against mutagenicity and carcinogenicity in the large intestine. We further discuss the impact of DNA repair on the dose-response relationship in colorectal carcinogenesis in view of recent studies, demonstrating the existence of 'no effect' point of departures (PoDs), i.e. thresholds for genotoxicity and carcinogenicity. The available data support the threshold concept for NOC with DNA repair being causally involved.

Carcinogenicity of consumption of red and processed meat: What about environmental contaminants?

In October 26, 2015, the International Agency for Research on Cancer (IARC) issued a press release informing of the recent evaluation of the carcinogenicity of red and processed meat consumption. The consumption of red meat and processed meat was classified as "probably carcinogenic to humans", and as "carcinogenic to humans", respectively. The substances responsible of this potential carcinogenicity would be generated during meat processing, such as curing and smoking, or when meat is heated at high temperatures (N-nitroso-compounds, polycyclic aromatic hydrocarbons and heterocyclic aromatic amines). However, in its assessments, the IARC did not make any reference to the role that may pose some carcinogenic environmental pollutants, which are already present in raw or unprocessed meat. The potential role of a number of environmental chemical contaminants (toxic trace elements, polycyclic aromatic hydrocarbons, polychlorinated dibenzo-p-dioxins and dibenzofurans, polychlorinated biphenyls, polybrominated diphenyl ethers, polychlorinated diphenyl ethers, polychlorinated naphthalenes and perfluoroalkyl substances) on the carcinogenicity of consumption of meat and meat products is discussed in this paper. A case-study, Catalonia (Spain), is specifically assessed, while the influence of cooking on the concentrations of environmental pollutants is also reviewed. It is concluded that although certain cooking processes could modify the levels of chemical contaminants in food, the influence of cooking on the pollutant concentrations depends not only on the particular cooking process, but even more on their original contents in each specific food item. As most of these environmental pollutants are organic, cooking procedures that release or remove fat from the meat should tend to reduce the total concentrations of these contaminants in the cooked meat.

Processed meat: the real villain?

Meat is a food rich in protein, minerals such as iron and zinc as well as a variety of vitamins, in particular B vitamins. However, the content of cholesterol and saturated fat is higher than in some other food groups. Processed meat is defined as products usually made of red meat that are cured, salted or smoked (e.g. ham or bacon) in order to improve the durability of the food and/or to improve colour and taste, and often contain a high amount of minced fatty tissue (e.g. sausages). Hence, high consumption of processed foods may lead to an increased intake of saturated fats, cholesterol, salt, nitrite, haem iron, polycyclic aromatic hydrocarbons, and, depending upon the chosen food preparation method, also heterocyclic amines. Several large cohort studies have shown that a high consumption of processed (red) meat is related to increased overall and cause-specific mortality. A meta-analysis of nine cohort studies observed a higher mortality among high consumers of processed red meat (relative risk (RR) = 1·23; 95 % CI 1·17, 1·28, top v. bottom consumption category), but not unprocessed red meat (RR = 1·10; 95 % CI 0·98, 1·22). Similar associations were reported in a second meta-analysis. All studies argue that plausible mechanisms are available linking processed meat consumption and risk of chronic diseases such as CVD, diabetes mellitus or some types of cancer. However, the results of meta-analyses do show some degree of heterogeneity between studies, and it has to be taken into account that individuals with low red or processed meat consumption tend to have a healthier lifestyle in general. Hence, substantial residual confounding cannot be excluded. Information from other types of studies in man is needed to support a causal role of processed meat in the aetiology of chronic diseases, e.g. studies using the Mendelian randomisation approach.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) formation and fate: an example of the coordinate contribution of lipid oxidation and Maillard reaction to the production and elimination of processing-related food toxicants

Major chemical reactions dealing with carbonyl chemistry in foods (Maillard reaction and lipid oxidation) play a role in PhIP formation and fate, pointing to this and analogous heterocyclic aromatic amines as outcomes of this chemistry.