Changes in moisture, colour, residual nitrites and N-nitrosamine accumulation of bacon induced by nitrite levels and dry-frying temperatures

Immobilization of horseradish peroxidase on UiO-66-NH2 for colorimetric and fluorometric sensing of nitrite

Immobilized enzymes play a crucial role in analytical sensing due to their exceptional stability and considerable commercial importance. In this study, a stable Zr-based metal-organic framework (UiO-66-NH2) was prepared as an immobilization platform for horseradish peroxidase (HRP) through covalent binding. HRP@UiO-66-NH2 retained 75% of its activity after 10 cycles. Subsequently, a colorimetric/fluorometric dual-mode sensing strategy using HRP@UiO-66-NH2 was developed for nitrite detection. HRP@UiO-66-NH2 facilitated the transformation of the non-colored compound 3,3',5,5'-tetramethylbenzidine (TMB) into its blue oxidized form. When nitrite is added, oxidized TMB (ox-TMB) specifically engaged with nitrite (NO2-) to generate diazotized TMB, leading to a color shift from blue to yellow. Concurrently, NO2- reacted with the amino groups of HRP@UiO-66-NH2, forming diazonium compounds and suppressing the fluorescence of HRP@UiO-66-NH2. The limits of detection were 0.21 μM and 0.19 μM for the colorimetric and fluorometric strategies, respectively. Furthermore, a portable kit for detecting nitrite was created by integrating gelatin with HRP@UiO-66-NH2. The kit could visually identify nitrite from 10-400 μM in colorimetric mode and 0-400 μM in fluorometric mode. This method provides an innovative approach for nitrite sensing, paving the way for new research into multifunctional immobilized enzymes and their potential uses in biochemical sensing applications.

Investigating flavor and quality characteristics in Chinese bacon from different regions using integrated GC-IMS, electronic sensory assessment, and sensory analysis

To investigate the variance in the quality and flavor profiles of bacon from different regions, gas chromatography-ion mobility spectrometry and electronic sensory techniques (including electronic nose and tongue [e-nose and e-tongue, respectively]) were employed for the flavor analysis of the sourced bacon samples. Both the e-nose and e-tongue successfully distinguished the aromas and flavors of different bacon varieties. Additionally, organic sulfides, aromatic benzenes, and short-chain alkanes, were more abundant in different bacon types. Employing GC-IMS technology, identified 52 volatile flavor compounds within diverse bacon samples, culminating in the establishment of a distinct fingerprint for each individual sample. The relative odor activity value identified 1-propene-3-methylthio, 2-heptanone, phenylacetaldehyde, furfuryl methyl sulfide, and 1-octene as the primary contributors to bacon flavor. These flavor substances were the main cause of the differences in bacon flavor in different regions. The interaction of volatile flavor compounds resulted in notable disparities between the odor profiles detected using the e-nose and e-tongue, even among bacon with similar volatile flavor constituents. In addition, the color and texture of the bacon varied significantly. Bacon from HB (Hubei), YN (Yunnan), and CQ (Chongqing) showed darkness in color. Meanwhile, the hardness of bacon from HN (Hunan), HB (Hubei), and SC (Sichuan) was relatively low. These results not only provide theoretical and technical insights for bacon flavor identification and control but also offer a foundation for consumers to make informed choices when purchasing bacon.

Application of lysine as a potential alternative to sodium salt in frankfurters: With emphasis on quality profile promotion and saltiness compensation

This study aimed to investigate the effect of lysine (Lys) on quality profile promotion and saltiness compensation in reduced‑sodium salt frankfurters. The results showed that the cooking loss of reduced‑sodium salt frankfurters decreased from 5.63 to 3.45% when the Lys level increased from 0.1 to 0.7%, as well as enhanced water contents and saltiness in a Lys dose-dependent manner. Moreover, the corresponding peak area percentage (A21) of reduced‑sodium salt frankfurters remarkably increased from 79.63% to 81.48% with the increased level of Lys. However, a higher level of Lys (≥ 0.5%) obviously reduced the textural properties of reduced‑sodium salt frankfurters, which was clearly verified by looser and rougher microstructures. Furthermore, hydrogen bonds were found to be the dominant molecular force in Lys-added reduced‑sodium salt frankfurters. Meanwhile, 0.3% Lys was found to exhibit the optimal sodium salt-replacing effect due to the highest degree of quality profile promotion and saltiness compensation. Additionally, directional triangle sensory evaluation further confirmed that the reduced‑sodium salt frankfurters treated with 0.3% Lys was perceived to be similar to control frankfurters, resulting a 50% salt-reduction effect. Thus, our results suggested that Lys could be applied as an efficient sodium salt alternative in reduced‑sodium salt frankfurters.

Effects of basic amino acids on heterocyclic amines and quality characteristics of fried beef patties at low NaCl level

The impact of basic amino acids (Lysine, Arginine, Histidine) on the formation of total heterocyclic amines (HAs) was investigated in fried beef patties at 1% NaCl level. Different levels of basic amino acids (0.1%, 0.5%, 1%) significantly inhibited the formation of the total and individual HAs at 1% NaCl, and the inhibitory effect was more effective than 3% NaCl (6.19 ng/g, 26.93% inhibition) (P < 0.05). Lys at 1% reduced total HAs the most (2.46 ng/g, 70.88% inhibition), followed by 1% His (2.79 ng/g, 67.03% inhibition) and 1% Arg (3.43 ng/g, 59.51% inhibition). Compared to the 3% NaCl, the quality characteristics (moisture content, frying loss, texture profile, and color) of the fried beef patties were significantly improved when basic amino acids were added at 1% NaCl (P < 0.05). The lipid oxidation of fried beef patties was significantly inhibited by 1% Arg and 1% Lys at 1% NaCl level (P < 0.05). The results indicated that basic amino acids could inhibit the formation of total HAs while maintaining the quality of meat products at low NaCl condition.

Chronic daily intake, probabilistic carcinogenic risk assessment and multivariate analysis of volatile N-nitrosamines in chicken sausages

Volatile N-nitrosamines (VNAs) are probably and possibly carcinogenic compounds to humans and widely found in processed meat products. In this study, the dietary exposure distribution and probabilistic cancer risk for main VNAs (N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosomethylethylamine, N-nitrosopiperidine, N-nitrosodibutylamine, and N-nitrosodi-n-propylamine) were calculated by Monte Carlo simulation (MCS). The lowest and highest mean concentrations of these six NAs were related to NDBA and NDEA as 0.350 and 2.655 μg/kg, respectively. In the 95th percentile, chronic daily intake of total VNAs for children (3-14 years) and adults (15-70 years) were calculated to be 2.83 × 10-4 and 5.90 × 10-5 mg/kg bw/day, respectively. The cancer risk caused by the consumption of chicken sausages was less than 10-4, indicating low concern for the Iranian population. According to principal component analysis and heat map results, NDEA, NPIP and frying showed a positive correlation, highlighting that the variables follow a similar trend.

Assessment of nitrosamine exposure in Korean foods: analysis, risk evaluation, and implications

This study investigated the presence of nitrosamines, known carcinogens, in 1320 food samples from South Korea using LC-APCI-MS/MS analysis. Results showed nitrosamines were detected in 72% of samples, with processed foods exhibiting higher levels. Sesame oil, snow white rice cake, fried chicken wings, and fried squid were identified as having the highest nitrosamine content. Daily intake estimates revealed nitrosodiethylamine (NDEA), nitrosodibutylamine (NDBA), and nitrosopyrrolidine (NPYR) as major contributors to exposure. Risk assessment, based on BMDL10 values and MOE calculations, indicated low health risks overall, but certain food groups at the 95th percentile showed MOEs below the safety threshold, warranting attention. This underscores the need for ongoing monitoring and regulation of nitrosamine levels in food products to protect public health, particularly in regions with high consumption of processed foods like South Korea. Further research and regulatory measures are crucial to minimize nitrosamine exposure and mitigate associated health risks.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-024-01651-8.

Back propagation artificial neural network (BP-ANN) for prediction of the quality of gamma-irradiated smoked bacon

This study investigated the effect of gamma irradiation on smoked bacon quality during storage and developed a multi-quality prediction model based on gamma irradiation. Gamma irradiation reduced moisture content and improved the microbial safety of smoked bacon. It also accelerated protein and lipid oxidation and altered free amino acids and fatty acids composition. It was effective in slowing down quality deterioration and sensory quality decline during storage. The backpropagation artificial neural network (BP-ANN) model was constructed by using physical and chemical indicators, irradiation dose, and storage time as input variables, and the total number of colonies and sensory scores as output layers. The transfer functions of the input-hidden layer and hidden-output layer were ReLu and Sigmoid, respectively. There were 13 neurons in the hidden layer. Results showed that BP-ANN based on physical and chemical indicators, irradiation dose, and storage time had great potential in predicting the multiple quality of smoked bacon.

Synchronous fluorescence detection of nitrite in meat products based on dual-emitting dye@MOF and its portable hydrogel test kit

A novel ratiometric fluorescent nanoprobe (Rh6G@UIO-66-NH2) was fabricated for efficient nitrite (NO2-) detection in the present study. When NO2- was introduced, it interacted with the amino groups on the surface of Rh6G@UIO-66-NH2, forming diazonium salts that led to the quenching of blue fluorescence. With this strategy, a good linear relationship between NO2- concentration and the fluorescent intensity ratio of the nanoprobe in the range of 1-100 μM was established, with a detection limit of 0.021 μM. This dual-readout nanosensor was applied to analyze the concentration of NO2- in real meat samples, achieving satisfactory recovery rates of 94.72-104.52%, highlighting the practical potential of this method. Furthermore, a portable Gel/Rh6G@UIO-66-NH2 hydrogel test kit was constructed for on-spot dual-mode detection of NO2-. This kit allows for convenient colorimetric analysis and fluorometric detection when used in conjunction with a smartphone. All the photos taken with the portable kit was converted into digital information using ImageJ software. It provides colorimetric and fluorescent visual detection of NO2- over a range of 0.1-1.5 mM, achieving a direct quantitative tool for NO2- identification. This methodology presents a promising strategy for NO2- detection and expands the application prospects for on-spot monitoring of food safety assessment.

Biogenic amines and volatile N-nitrosamines in Chinese smoked-cured bacon (Larou) from industrial and artisanal origins

This study aimed to compare biogenic amines (BAs), volatile N-nitrosamines (VNAs) and chemical properties of Chinese smoked-cured bacon (Larou) from industrial and artisanal sources. The results indicated that nitrite residues were low in artisanal Larou, whereas the salt content was relatively high in all samples. The family-made Larou accumulated high levels of BAs and probably present a health risk. Additionally, phenylethylamine exceeded 30 mg/kg in 4 out of 5 industrial Larou samples, whereas, 9 VNAs concentrations were low and unlikely to induce adverse health effects on consumers. Principal component analysis revealed that the industrial Larou products had similar safety properties in terms of BAs and VNAs content when compared to the family-made samples. Correlation analysis indicated that BAs and VNAs were significantly correlated with free amino acids, a_w, pH and NaCl, respectively. This study suggests that the quality of Larou needs to be further improved by reducing salt and BAs content.

Advanced Glycation End Products and Nitrosamines in Sausages Influenced by Processing Parameters, Food Additives and Fat during Thermal Processing

Advanced glycation end products (AGEs) and nitrosamines (NAs) in sausage are associated with pathogenic and carcinogenic risks. However, the multiple reaction parameters affecting the production of AGEs and NAs during sausage processing remain unclear. This experiment evaluated the effects of processing parameters, food additives and fat ratios on the formation of AGEs and NAs in sausages. The results showed a 2-3-fold increase in N^ε-(carboxymethyl)lysine (CML) and N^ε-(carboxyethyl)lysine (CEL) when the sausage processing temperature was increased from 90 °C to 130 °C, and N-nitrosodimethylamine (NDEA) increased from 3.68 ng/g to 6.41 ng/g. The addition of salt inhibited the formation of AGEs and NAs, and the inhibitory ability of 2 g/100 g of salt was 63.6% for CML and 36.5% for N-nitrosodimethylamine (NDMA). The addition of 10 mg/kg nitrite to sausages reduced CML formation by 43.9%, however, nitrite had a significant contribution to the formation of NAs. The addition of fat only slightly contributed to the production of CML. In addition, the relationship between α-dicarbonyl compounds and the formation of AGEs was investigated by measuring the changes in α-dicarbonyl compounds in sausages. The results showed two trends of AGEs and α-dicarbonyl compounds: AGEs increased with the increase in α-dicarbonyl compounds and AGE level increased but α-dicarbonyl compound level decreased.

The Generation of Nitric Oxide from Aldehyde Dehydrogenase-2: The Role of Dietary Nitrates and Their Implication in Cardiovascular Disease Management

Reduced bioavailability of the nitric oxide (NO) signaling molecule has been associated with the onset of cardiovascular disease. One of the better-known and effective therapies for cardiovascular disorders is the use of organic nitrates, such as glyceryl trinitrate (GTN), which increases the concentration of NO. Unfortunately, chronic use of this therapy can induce a phenomenon known as "nitrate tolerance", which is defined as the loss of hemodynamic effects and a reduction in therapeutic effects. As such, a higher dosage of GTN is required in order to achieve the same vasodilatory and antiplatelet effects. Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is a cardioprotective enzyme that catalyzes the bio-activation of GTN to NO. Nitrate tolerance is accompanied by an increase in oxidative stress, endothelial dysfunction, and sympathetic activation, as well as a loss of the catalytic activity of ALDH2 itself. On the basis of current knowledge, nitrate intake in the diet would guarantee a concentration of NO such as to avoid (or at least reduce) treatment with GTN and the consequent onset of nitrate tolerance in the course of cardiovascular diseases, so as not to make necessary the increase in GTN concentrations and the possible inhibition/alteration of ALDH2, which aggravates the problem of a positive feedback mechanism. Therefore, the purpose of this review is to summarize data relating to the introduction into the diet of some natural products that could assist pharmacological therapy in order to provide the NO necessary to reduce the intake of GTN and the phenomenon of nitrate tolerance and to ensure the correct catalytic activity of ALDH2.

Bio-Doped Microbial Nanosilica as Optosensing Biomaterial for Visual Quantitation of Nitrite in Cured Meats

A microbial optosensor for nitrite was constructed based on biomimetic silica nanoparticles, which were doped with R5, a polypeptide component of silaffin, as a robust biosilica immobilization matrix entrapped with Raoultella planticola and NAD(P)H cofactor during the in vitro biosilicification process of silica nanoparticles. Ruthenium(II)(bipy)2(phenanthroline-benzoylthiourea), the chromophoric pH probe, was physically adsorbed on the resulting biogenic nanosilica. Optical quantitation of the nitrite concentration was performed via reflectance transduction of the bio-doped microbial nanosilica at a maximum reflectance of 608 nm, due to the deprotonation of phen-BT ligands in the ruthenium complex, while the intracellular enzyme expression system catalyzed the enzymatic reduction of nitrite. Reflectance enhancement of the microbial optosensor was linearly proportional to the nitrite concentration from 1−100 mg L−1, with a 0.25 mg L−1 limit of detection and a rapid response time of 4 min. The proposed microbial optosensor showed good stability of >2 weeks, great repeatability for 5 repetitive assays (relative standard deviation, (RSD) = 0.2−1.4%), high reproducibility (RSD = 2.5%), and a negligible response to common interferents found in processed meats, such as NO3−, NH4+, K+, Ca2+, and Mg2+ ions, was observed. The microbial biosensor demonstrated an excellent capacity to provide an accurate estimation of nitrite in several cured meat samples via validation using a standard UV-vis spectrophotometric Griess assay.

Effect of plant polyphenols on the physicochemical properties, residual nitrites, and N-nitrosamine formation in dry-fried bacon

Tea polyphenol (TP), apple polyphenol (AP), and cinnamon polyphenol (CP) are all enriched with antioxidant components, present enormous potential as natural antioxidants in meat products. The objective of this study was to evaluate the physicochemical properties, residual nitrites, and formation of N-nitrosamine (NA) in dry-fried bacons with three aforementioned plant polyphenols and ascorbic acid (AA). The results show that both plant polyphenols and AA significantly reduced pH, lipid oxidation and residual nitrite content when compared to the control (P < 0.05). Only AP exhibited a protective effect against protein oxidation-induced damage in bacon, and N-nitroso-methyl phenylamine (NMPhA) contents were significantly affected by plant polyphenols (P < 0.05). Bacon containing 300 mg/kg AP produced less thiobarbituric acid reactive substance (TBARS) (0.59 MDA/kg), carbonyl contents (2.30 nmol/mg protein) and NMPhA formation (1.211 ng/kg). In conclusion, plant polyphenols, particularly AP, have the potential to be used as natural antioxidants for reducing oxidation and nitrite application level while also improving the safety of bacon.

Olive Leaf Extract (OLE) Addition as Tool to Reduce Nitrate and Nitrite in Ripened Sausages

Olive leaf extract (OLE) is known to be a source of phenolic compounds with antioxidant and antimicrobial activities. This study investigated the effects of the OLE addition to reduce nitrate/nitrite (NO) content on the physico-chemical features of ripened pork sausages. Seven formulations of pork sausages were set up: CTRL (0 mg/kg OLE; 300 mg/kg NO), Tr1 (200 mg/kg OLE; 150 mg/kg NO), Tr2 (400 mg/kg OLE; 150 mg/kg NO), Tr3 (800 mg/kg OLE; 150 mg/kg NO), Tr4 (200 mg/kg OLE; 0 mg/kg NO), Tr5 (400 mg/kg OLE; 0 mg/kg NO), and Tr6 (800 mg/kg OLE; 0 mg/kg NO). At the end of the ripening period, all the samples were within hygienic limits and the substitution of the additives with OLE allowed the reduction of NO residual contents. Both OLE and NO influenced the colour parameters. At the highest dose of OLE, both alone and in combination with reduced dose of NO, no significant differences in terms of moisture, pH, and aw were found compared to CTRL. In absence of NO, a significant reduction of weight loss was observed. Moreover, in the samples without NO a reduction of the hardness was detected. Finally, the oxidative stability test showed that the increase of the OLE amount prolonged the induction time.

Nitrosamines and Polycyclic Aromatic Hydrocarbons in Smoke-Cured Bacon (Larou) of Artisanal and Industrial Origin

The aim of this study was to compare the nitrosamines (NAs) and polycyclic aromatic hydrocarbons (PAHs) of Chinese smoke-cured bacon (Larou) of artisanal and industrial origin. The results showed that the average pH and Aw values of family-made Larou products were lower than those of industrial Larou, which was opposite to the TBARS level. The contents of residual nitrite and PAH4 in two artisanal Larou were significantly higher than those of the other groups (p < 0.05). The highest NA content (10.78 μg/kg) was found in family-made Larou. A correlation analysis indicated that the relationships between residual nitrite contents and total PAH8 contents (τ = 0.692, p < 0.01) and total NAs contents (τ = 0.805, p < 0.01) were characterized with a positive correlation. A principal component analysis indicated that the Larou from the industrial sources had similar safety attributes, and was more stable than the Larou processed in an artisanal manner. Our data suggest that Larou produced in industrial conditions is suitable for consumption.