Monitoring arsenic species concentration in rice-based processed products distributed in South Korean markets and related risk assessment.

Rice is an important grain as a major source of carbohydrates in Asia but contains more arsenic (As) than other grains. A total of 239 rice-based processed foods (rice, n = 30; rice cake, n = 30; porridge, n = 39; noodles, n = 33; bread, n = 20; snack, n = 59; powder, n = 28) were purchased in 2019 from domestic markets to measure total As (tAs) and As species. The average tAs and inorganic As (iAs) in each sample group ranged from 20 to 180 µg/kg (porridge for baby to noodle) and 4.4-85 µg/kg (porridge for baby to powder), respectively. The correlation between the iAs and tAs was affected by the variety of ingredients, such as the presence of seaweed (tAs) and the milling type of rice (iAs). Although rice cakes and baby rice-based powders are a source of concern for both adults and children, respectively, risk assessments indicate that most rice-based foods are generally safe to consume in South Korea. Supplementary Information: The online version contains supplementary material available at 10.1007/s10068-023-01270-9.

Immune-enhancing effects of ß-lactoglobulin glycated with lactose following in vitro digestion on cyclophosphamide-induced immunosuppressed mice.

ß-Lactoglobulin (ß-LG) is a major milk protein, making up more than 53% of the total whey proteins, and is seen as a valuable ingredient in food processing because of its high essential amino acid content and diverse functional applications. The Maillard reaction can occur during the storage and processing of food and generate various beneficial effects, including anti-allergenicity, antioxidant, and immunomodulatory effects. The addition of an ß-LG-lactose conjugate (LGL) produced by the Maillard reaction was shown to have a strong immune-enhancing effect, increasing both nitric oxide generation and cytokine expression through activation of RAW 264.7 cells, even after in vitro digestion. Furthermore, daily LGL administration resulted in the upregulation of several immune markers in a cyclophosphamide-induced immunosuppressive mouse model, indicating that this treatment stimulates multiple immune cells, including macrophages, natural killer cells, and lymphocytes, enhancing the proliferation and activation of both the innate and adaptive immune responses. Taken together, these findings indicate that consuming LGL on a regular basis can improve immunity by increasing the natural production of various immune cells.

Characterization of macrophage stimulating compound in glycated whey protein concentrate.

Whey, a by-product of cheese making, is a collection of several milk proteins and has functional and nutritional values. Whey protein concentrate (WPC) exhibits various functional effects by glycation. Studies to find sugar-binding sites in a protein having a functional effect are reported. However, it is rarely clear whether it confirms that glycated single protein exhibits the same effect of protein cluster. This study confirmed which protein sites are responsible for the effect of glycated WPC (G-WPC). ß-Lactoglobulin (LG) was the major protein of G-WPC and glycated with lactose. The glycated LG increased the nitric oxide and cytokine secretion similar to G-WPC and peptide sequences of active compound was confirmed using the high molecular weight band of G-WPC. The K151 and K157 residues of LG were modified by glycation with sugar in common with G-WPC. These residues of glycated LG potentially contribute to the immune-modulation effect of G-WPC.

Anti-inflammatory activities of Maillard reaction products from whey protein isolate fermented by Lactobacillus gasseri 4M13 in lipopolysaccharide-stimulated RAW264.7 cells.

Maillard reaction products formed from whey protein isolate (WPI) and sugar have been shown to have an anti-inflammatory effect in vitro. Here, we incubated WPI and galactose (GWA) in an aqueous solution at 65°C for 24 h to produce a glycated conjugate, which was then fermented using Lactobacillus gasseri 4M13 to obtain the fermented product (F-GWA). We demonstrated that F-GWA had an anti-inflammatory effect on lipopolysaccharide (LPS)-stimulated RAW264.7 cells. It reduced both LPS-stimulated nitric oxide production and LPS-stimulated increases in the gene expression levels of tumor necrosis factor-α and cyclooxygenase-2 in a dose-dependent manner. Furthermore, F-GWA inhibited the LPS-induced phosphorylation of extracellular signal-regulated kinase and c-Jun N-terminal kinase, members of the mitogen-activated protein kinase family. The glycation process was evaluated by measuring fluorescence intensity and the furosine concentration during the Maillard reaction to form GWA. The protein modifications of WPI were analyzed using MALDI-TOF tandem mass spectrometry. We found that the combination of the Maillard reaction and L. gasseri 4M13 fermentation increased the prebiotic properties of GWA as well as organic acid production, compared with the nonreacted WPI and galactose.

Comparing levels of perfluorinated compounds in processed marine products.

Perfluorinated compounds (PFCs) are widely distributed in nature and have many applications due to their unique chemical and physicochemical properties. While, PFCs are present in soil, water, and air, their pathway for entry into the human body is circumstantially via contaminated food. The demand for seafood has been increasing. In this study, we investigated via LC-MS/MS, the content of 19 different types of PFCs in 302 samples belonging to five different categories of the typical South Korean seafood. The highest levels of PFOA, PFTrDA, PFOS, and PFPeA were found in dried seafood, canned and salted seafood, processed fish food, and seasoned laver, respectively. The levels of PFOA and PFOS were compared on the basis of various criteria including the nomenclature, biological classification, and habitat of the source of seafood. High levels of PFOA and PFOS were detected in anchovy, sea squirt, and mackerel based on the nomenclature of raw seafood, in crustaceans based on the biological classification, and in demersal organisms based on the habitat. The human intake values of PFOA and PFOS from the processed marine products in South Korea were lower than the tolerable daily intake, indicating that the consumption of these processed seafood poses no immediate harm.

Enhancing the natural killer cell activity and anti-influenza effect of heat-treated Lactobacillus plantarum nF1-fortified yogurt in mice.

Influenza A virus (IAV) infection is a global public health concern. It causes respiratory diseases ranging from mild illness to fatal disease. Natural killer (NK) cells are an innate immune component that kill infected cells and secrete cytokines to modulate the adaptive immune system; they constitute the first-line defense and play important roles in controlling IAV infection. This study evaluated the effect of daily administration of heat-treated Lactobacillus plantarum nF1-fortified yogurt on immunity and protection against IAV infection. Mice administered with heat-treated L. plantarum nF1-fortified yogurt showed elevated NK cell-related cytokine expression levels. Daily administration of the L. plantarum nF1-fortified yogurt before IAV infection also enhanced splenic NK activity, lung inflammatory cytokine responses, and survival rate. Thus, daily administration of nF1-fortified yogurt enhances host immunity and helps prevent IAV infection.

Anti-inflammatory effect of sugar-amino acid Maillard reaction products on intestinal inflammation model in vitro and in vivo.

The Maillard reaction is a nonenzymatic reaction between an amino acid and a reducing sugar that usually occurs upon heating. This reaction occurs routinely in cooking, generates numerous products, which are collectively referred to as Maillard reaction products (MRPs) contributing to aroma and color features. Advanced glycation end-products (AGEs) transformed from MRPs are participated in many types of inflammation reaction. In this study, various sugar-amino acid MRPs were prepared from three different amino acids (lysine, arginine, and glycine) and sugars (glucose, fructose, and galactose) for 1 h with heating at 121 °C. Treatment of lipopolysaccharide-stimulated RAW264.7 macrophages with the MRPs decreased nitric oxide (NO) expression compared to control without MRPs treatment. MRPs derived from lysine and galactose (Lys-Gal MRPs) significantly inhibited NO expression. The retentate fraction of Lys-Gal MRPs with cut-off of molecular weight of 3-10 kDa (LGCM) suppressed NO expression more effectively than did Lys-Gal MRPs. The anti-inflammatory effect of LGCM was evaluated using a co-culture system consisting of Caco-2 (apical side) and RAW264.7 or THP-1 (basolateral side) cells to investigate the gut inflammation reaction by stimulated macrophage cells. In this system, LGCM prevented a decreased transepithelial electrical resistance, and decreased both tumor necrosis factor-α production in macrophages and interleukin (IL)-8 and IL-1ß mRNA expression in Caco-2 cells. In co-culture and in vivo dextran sulfate sodium (DSS)-induced colitis model study, we also observed the anti-inflammatory activity of LGCM.

Characterization of Maillard-type lysozyme-galactomannan conjugate having immune-enhancing effects.

In the present study, lysozyme-galactomannan conjugate (LGC) was fractionated by ion-exchange chromatography, the immune activity of the fractions was confirmed, and a structural analysis of the glycoprotein was performed. A high-molecular-weight fraction of LGC (H-LGC), was characterized by using a method using matrix-assisted laser desorption/ionization time of flight mass spectrometry. The glycated site of H-LGC was determined to be the lysine (Lys)115 residue. In addition, about 1mol of galactomannan (G) was linked to 1mol of lysozyme (L) in LGC based on the binding weight ratio. Conjugation of L and G reduced the aggregation of particles, resulting in a monodispersion based on measurement of dynamic light scattering. LGC in solution showed heterogeneous shapes with a mean size of 337nm. Therefore, we suggest that LGC improves the immune-enhancing activity as G conjugates the site of Lys115 on L, and provides higher solubility with reduced aggregation for the industrial use of LGC as a food constituent.

Protective Effects of Maillard Reaction Products of Whey Protein Concentrate against Oxidative Stress through an Nrf2-Dependent Pathway in HepG2 Cells.

Whey protein concentrate (WPC), which contains α-lactalbumin and ß-lactoglobulin, is utilized widely in the food industry. The Maillard reaction is a complex reaction that produces Maillard reaction products (MRPs), which are associated with the formation of antioxidant compounds. In this study, the hepatoprotection activity of MRPs of WPC against oxidative stress through the nuclear factor-E2-related factor 2 (Nrf2)-dependent antioxidant pathway in HepG2 cells was examined. Glucose-whey protein concentrate conjugate (Glc-WPC) was obtained from Maillard reaction between WPC and glucose. The fluorescence intensity of Glc-WPC increased after 7 d compared to native WPC, and resulted in loss of 48% of the free amino groups of WPC. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns of Glc-WPC showed the presence of a high-molecular-weight portion. Treatment of HepG2 cells with Glc-WPC increased cell viability in the presence of oxidative stress, inhibited the generation of intracellular reactive oxygen species by tert-butyl hydroperoxide (t-BHP), and increased the glutathione level. Nrf2 translocation and Nrf2, reduced nicotinamide adenine dinucleotide phosphate (NAD(P)H)-quinone oxidoreductase 1 (NOQ1), heme oxygenase-1 (HO-1), glutamate-L-cysteine ligase (GCL)M and GCLC mRNA levels were increased by Glc-WPC. Also, Glc-WPC increased the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 and c-Jun N-terminal kinase (JNK). The results of this study demonstrate that Glc-WPC activates the Nrf2-dependent pathway through the phosphorylation of ERK1/2 and JNK in HepG2 cells, and induces production of antioxidant enzymes and phase II enzymes.

Effects of Glycated Whey Protein Concentrate on Pro-inflammatory Cytokine Expression and Phagocytic Activity in RAW264.7 Macrophages.

The aim of this study was to determine the stimulatory effects of Maillard reaction, a non-enzymatic browning reaction on the expression of pro-inflammatory cytokines and phagocytic activity induced by whey protein concentrate (WPC). Glycated WPC (G-WPC) was prepared by a reaction between WPC and the lactose it contained. The fluorescence intensity of G-WPC dramatically increased after one day, and high molecular weight complexes formed via the Maillard reaction were also observed in the sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles. G-WPC demonstrated immunomodulatory effects, including stimulation of increased nitric oxide production and cytokine expressions (i.e., tumor necrosis factor-α, interleukin (IL)-1ß, and IL-6), compared to WPC. Furthermore, the phagocytic activity of RAW264.7 cells was significantly increased upon treatment with G-WPC, compared to WPC. Therefore, we suggest that G-WPC can be utilized as an improved dietary source for providing immune modulating activity.

Immune enhancing effect of a Maillard-type lysozyme-galactomannan conjugate via signaling pathways.

We studied the immune-modulating effect of Maillard-type lysozyme-galactomannan conjugate (LGC). LGC significantly induced nitric oxide, and expressions of tumor necrosis factor (TNF)-α, interleukin (IL)-1ß and IL-8 on the murine macrophage Raw 264.7 cell line. In the mechanism of LGC, while extracellular signal-regulated kinase (ERK) was important for the induction of TNF-α, IL-1ß and IL-8, the phosphorylation of C-Jun NH2-termianl kinase (JNK) contributed to the induction of TNF-α and IL-1ß to a greater degree. These cytokines were less sensitive to the inhibition of p38. Nuclear factor (NF)-κB was involved in the induction of TNF-α and IL-1ß. These data indicate that LGC has immune-modulating effects via JNK, ERK and NF-κB pathways, and that LGC may contribute to host immune defense.