Keizo Arihara

Strategies for designing novel functional meat products.

In recent years, much attention has been paid to physiological functions of foods due to increasing concerns for health. Although there has been limited information of physiological functions of meat until recently, several attractive meat-based bioactive compounds, such as carnosine, anserine, l-carnitine, conjugated linoleic acid, have been studied. Emphasizing these activities is one possible approach for improving the health image of meat and developing functional meat products. This article provides potential benefits of representative meat-based bioactive compounds on human health and an overview of meat-based functional products. Strategies for designing novel functional meat products utilizing bioactive peptides and/or probiotic bacteria, is also discussed. This article focuses particularly on the possibility of meat protein-derived bioactive peptides, such as antihypertensive peptides. There are still some hurdles in developing and marketing novel functional meat products since such products are unconventional and consumers in many countries recognize meat and meat products to be bad for health. Along with accumulation of scientific data, there is an urgent need to inform consumers of the exact functional value of meat and meat products including novel functional foods.

Damage of yeast cells induced by pulsed light irradiation

DNA damage, such as formation of single strand breaks and pyrimidine dimers was induced in yeast cells after irradiation by pulsed light, which were essentially the same as observed with continuous ultraviolet (UV) light. The UV-induced DNA damage is slightly higher than seen with pulsed light. However, increased concentration of eluted protein and structural change in the irradiated yeast cells were observed only in the case of pulsed light. A difference in the inactivation effect between pulsed light and UV light was found and this suggested cell membrane damage induced by pulsed light irradiation. It is proposed that pulsed light can be used as an effective sterilizing method for the yeast Saccharomyces cerevisiae.

Effect of intestinal Lactobacillus starter cultures on the behaviour of Staphylococcus aureus in fermented sausage

The effects of Lactobacillus strains isolated from intestinal tracts for starter cultures of fermented sausage on the growth rate and enterotoxin production of Staphylococcus aureus were studied at two fermentation temperatures of 20 degrees C and 35 degrees C. Initial inoculated populations in the sausage batter were approx. 10(4) cfu/g for S. aureus and 10(7) cfu/g for the Lactobacillus strain as a starter culture. Samples of sausage were taken during fermentation and analyzed for pH and microbial populations. In control lots without inoculation of Lactobacillus strains, staphylococcal enterotoxin was detected during fermentation at each temperature. Of three intestinal Lactobacillus strains, L. rhamnosus FERM P-15120 and L. paracasei subsp. paracasei FERM P-15121 inhibited the growth and enterotoxin production of S. aureus in sausages during fermentation at both temperatures, although L. acidophilus FERM P-15119 could not satisfactorily suppress them. The effect of the two selected strains in meat fermentation (i.e., fermentation time, acid production, inhibition of S. aureus) was the same as that of a commercial L. sake starter culture for fermented sausage. These results suggest the intestinal Lactobacillus strains selected in this study could be utilized as a starter culture to produce new fermented meat products that are microbiologically safe.

Uptake and recovery of gold ions from electroplating wastes using eggshell membrane

The animal byproduct, hen eggshell membrane (ESM), was evaluated for its ability to sorb gold ions (dicyanoaurate(I) and tetrachloroaurate(III)) from solutions and electroplating wastewater. The gold uptake was dependent on pH, temperature and co-ions present in the solutions, with pH 3.0 being the optimum value. The equilibrium data followed the Langmuir isotherm model with maximum capacities of 147 mg Au(I)/g dry weight and 618 mg Au(III)/g, respectively. Desorption of sorbed gold(I) with 0.1 mol/l NaOH resulted in no changes of the biosorbent gold uptake capacity through five consecutive sorption/desorption cycles. In column experiments, selective recovery of gold from electroplating wastewater containing various metal ions was noted. The affinity of metal sorption was in the order Au > Ag > Co > Cu > Pb > Ni > Zn.

Antihypertensive effect and antioxidant activity of peptide fractions extracted from Spanish dry-cured ham

This study examined the antihypertensive and antioxidant activities of water soluble fractions of a Spanish dry-cured ham extract. Antihypertensive activity of a fractionated peptide extract, by size-exclusion chromatography was determined by measuring changes in systolic blood pressure of spontaneously hypertensive rats after oral administration. Every sample exhibited antihypertensive activity, pooled fractions corresponding to 1700 Da or lower were the most antihypertensive with a decrease of 38.38 mm Hg in systolic blood pressure. In vitro experiments revealed marked in vitro angiotensin I-converting enzyme inhibitory activity in fractions corresponding to these elution volumes. Some of the fractions exhibited great 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity, ranging from 39% to 92% as well as superoxide ion extinguishing ability with values ranging from 41.67% to 50.27% of the antioxidant activity, suggesting the presence of peptides with antioxidant activity. These findings suggest that Spanish dry-cured ham contains peptides with antioxidant and antihypertensive activities.

Angiotensin I-Converting Enzyme Inhibitory Peptides Generated from in Vitro Gastrointestinal Digestion of Pork Meat

The main purpose of this work was to study the generation of Angiotensin I-converting enzyme inhibitory (ACEI) peptides after gastrointestinal digestion of pork meat by the action of pepsin and pancreatin at simulated gut conditions. The hydrolysate was further subjected to reverse phase chromatography in order to separate the fractions with ACEI activity. Using MALDI-TOF/TOF mass spectrometry, 12 peptides were identified in these fractions. It is worth highlighting the novel peptides ER, KLP, and RPR with IC(50) values of 667 microM, 500 microM, and 382 microM, respectively. Results obtained by MALDI-TOF/TOF mass spectrometry were complemented by a second approach consisting of the analysis of the hydrolysate directly by nanoLC-ESI-MS/MS followed by a study of the obtained sequences and comparison with known ACEI peptide sequences. By using these two approaches, a total of 22 peptides were selected for its synthesis and further in vitro assay of ACEI activity. The strongest ACE inhibition was observed for peptide KAPVA (IC(50) = 46.56 microM) followed by the sequence PTPVP (IC(50) = 256.41 microM). Sequence similarity searches revealed that these two peptides derive from muscle titin, constituting the first identified ACEI peptides coming from this protein. This is also the first time that ACEI sequences MYPGIA and VIPEL have been reported. Other identified and synthesized sequences showed less ACEI activity. The obtained results evidence the potential of pork meat proteins as a source of antihypertensive peptides after gastrointestinal digestion.

Purification and Identification of antihypertensive peptides in Spanish dry-cured ham.

Novel sequences exhibiting in vitro ACE inhibitory activity as well as in vivo antihypertensive activity were identified from Spanish dry-cured ham. Water soluble peptide extracts from dry-cured ham were purified by size-exclusion chromatography and reversed-phase high performance liquid chromatography and then, further identification of sequences was carried out by nano-liquid chromatography coupled to tandem mass spectrometry. A total of 73 peptide sequences were identified from active fractions presenting 100% homology with different Sus scrofa skeletal muscle proteins. All identified peptides showed Mr between 374 and 1610 and amino acid sequences between 5 and 14 amino acids in length. Considering the low molecular mass and structural requirements for ACE inhibition some of the identified peptides were synthesised and their IC(50) calculated. The most potent peptide was found to be AAATP (IC(50) value of 100 μM). This peptide also showed good in vivo activity because it decreased systolic blood pressure by -25.62 ± 4.5 mmHg (p<0.05) in spontaneous hypertensive rats after 8 h administration. Other sequences yielded a moderate ACE inhibition. Results from this study show that Spanish dry-cured ham may represent a source of natural peptides with potential benefit for human health.

Egg Yolk Phosvitin Inhibits Hydroxyl Radical Formation from the Fenton Reaction

Phosvitin, a phosphoprotein known as an iron-carrier in egg yolk, binds almost all the yolk iron. In this study, we investigated the effect of phosvitin on Fe(II)-catalyzed hydroxyl radical (•OH) formation from H2O2 in the Fenton reaction system. Using electron spin resonance (ESR) with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and deoxyribose degradation assays, we observed by both assays that phosvitin more effectively inhibited •OH formation than iron-binding proteins such as ferritin and transferrin. The effectiveness of phosvitin was related to the iron concentration, indicating that phosvitin acts as an antioxidant by chelating iron ions. Phosvitin accelerates Fe(II) autoxidation and thus decreases the availability of Fe(II) for participation in the •OH-generating Fenton reaction. Furthermore, using the plasmid DNA strand breakage assay, phosvitin protected DNA against oxidative damage induced by Fe(II) and H2O2. These results provide insight into the mechanism of protection of the developing embryo against iron-dependent oxidative damage in ovo.

Photodynamic antimicrobial activity of avian eggshell pigments

Pigmentation in avian eggshells appears to be associated with shell strength, temperature regulation, and camouflage. The pigments found in eggshells are mainly porphyrins, which have been utilized therapeutically as photosensitizers. Here, we examined the photoinactivation of gram‐positive (Staphylococcus aureus, Bacillus cereus) and gram‐negative bacteria (Escherichia coli, Salmonella enteritidis) by hen eggshells and their pigments. The results indicated that eggshells have a light‐dependent antimicrobial activity against gram‐positive, but not gram‐negative, bacteria. Our results indicate the possibility that the natural pigments used therapeutically have evolved in nature as a defence system.

Antihypertensive activity of peptides identified in the in vitro gastrointestinal digest of pork meat.

This study investigated the in vivo antihypertensive activity of three novel peptides identified in the in vitro digest of pork meat. These peptides were RPR, KAPVA and PTPVP and all of them showed significant antihypertensive activity after oral administration to spontaneously hypertensive rats, RPR being the peptide with the greatest in vivo activity. To our knowledge, this is the first report showing the in vivo antihypertensive action of the three peptides from nebulin (RPR) and titin (KAPVA and PTPVP), thus confirming their reported in vitro angiotensin I-converting enzyme (ACE) inhibitory activity. These findings suggest that pork meat could constitute a source of bioactive constituents that could be utilized in functional foods or nutraceuticals.