In vitro influence of D/L-lactic acid, sodium chloride and sodium nitrite on the infectivity of feline calicivirus and of ECHO virus as potential surrogates for foodborne viruses

The importance of foodborne viruses is increasingly recognized. Thus, the effect of commonly used food preservation methods on the infectivity of viruses is questioned. In this context, we investigated the antiviral properties of d,l-lactic acid, sodium chloride and sodium nitrite by in vitro studies. Two model viruses, Feline Calicivirus (FCV) and Enteric Cytophatic Human Orphan (ECHO) virus, were chosen for this study simulating important foodborne viruses (human noroviruses (NoV) and human enteroviruses, resp.). The model viruses were exposed to different solutions of d,l-lactic acid (0.1-0.4% w/w, pH 6.0-3.2), of sodium chloride (2-20%, w/v) and of sodium nitrite (100, 150 and 200 ppm) at 4 and 20 °C for a maximum of 7 days. Different results were obtained for the two viruses. ECHO virus was highly stable against d,l-lactic acid and sodium chloride when tested under all conditions. On the contrary, FCV showed less stability but was not effectively inactivated when exposed to low acid and high salt conditions at refrigeration temperatures (4 °C). FCV titers decreased more markedly at 20 °C than 4 °C in all experiments. Sodium nitrite did not show any effect on the inactivation of both viruses. The results indicate that acidification, salting or curing maybe insufficient for effective inactivation of foodborne viruses such as NoV or human enteroviruses during food processing. Thus, application of higher temperature during fermentation and ripening processes maybe more effective toward the inactivation kinetics of less stable viruses. Nevertheless, more studies are needed to examine the antiviral properties of these preserving agents on virus survival and inactivation kinetics in the complex food matrix.     

Parenteral administration of glutamine modulates acute phase response in postparturient dairy cows

The objective of this study was to investigate whether administration of l-Gln would affect mediators of acute phase response in postparturient dairy cows. Twenty-four multiparous Holstein cows were blocked by the expected day of calving and randomly assigned to 1 of the 3 treatment groups (n = 8/group): 1) i.v. infusion of 10 L of 0.85% NaCl (control), 2) i.v. infusion of 106, or 3) 212 g/d of l-Gln mixed with 10 L of 0.85% NaCl solution; each treatment was given 8 h/d for each of 7 consecutive days starting on d 1 after calving. Blood samples were collected 1 wk before the expected day of parturition as well as on d 0, 7, 14, and 21 after parturition; plasma concentrations of serum amyloid A (SAA), haptoglobin, and lipopolysaccharide-binding protein were measured by ELISA, and α₁-acid glycoprotein was assessed by radial immunodiffusion. Concentrations of SAA, haptoglobin, and α₁-acid glycoprotein increased in control cows after parturition, reaching peak values on d 0 or 7 postpartum (60, 1,093, and 963 μg/mL, respectively). Cows infused with 106 g/d of l-Gln had greater concentrations of SAA in plasma on d 14 and 21 compared with controls (62.8 vs. 30.2 and 71.1 vs. 34.5 μg/mL, respectively). Cows infused with 212 g/d of l-Gln had greater concentrations of SAA on d 7 (82.5 vs. 53.9 μg/mL) and lower concentrations of haptoglobin on d 14 and 21 postpartum compared with controls (264 vs. 621 and 175 vs. 587 μg/mL, respectively). Cows treated with 106 and 212 g/d of l-Gln had greater plasma lipopolysaccharide-binding protein concentrations on d 7 compared with control group (50.0 and 35.6 vs. 10.8 μg/mL, respectively). There were no treatment differences with respect to milk yield and DM intake during the experimental period. In conclusion, our data indicate that i.v. administration of l-Gln modulated acute phase mediators in dairy cows after parturition and warrants further research into the mechanisms behind these effects.     

Effect of L-carnitine infusion and feed restriction on carnitine status in lactating Holstein cows

Previously we determined that abomasal infusion of l-carnitine increased in vitro hepatic fatty acid oxidation, decreased liver lipid accumulation, and supported higher fat-corrected milk yield in feed-restricted lactating cows. The objectives of this study were to examine the effects of supplemental l-carni-tine and amount of feed intake on free carnitine and carnitine ester concentrations in liver, muscle, milk, and plasma of lactating dairy cows. Eight lactating Holstein cows (132 ± 36 d in milk) were used in a replicated 4 × 4 Latin square design with 14-d periods to test factorial combinations of water or l-carnitine infusion (20 g/d; d 5 to 14) and ad libitum or restricted (50% of previous 5-d intake; d 10 to 14) dry matter intake. Plasma was obtained 3 times daily on d 4, 8, and 12; milk samples were collected on d 8, 9, 13, and 14. Liver and muscle were biopsied on d 14 of each period. Free carnitine, short-chain acylcarnitine, and long-chain acylcarnitine concentrations were determined using a radioenzymatic assay coupled with ion exchange chromatography. Abomasal l-carnitine infusion increased total carnitine in plasma on d 8 and d 12. All liver carnitine fractions were increased by carnitine infusion. Feed restriction elevated concentrations of free carnitine, long-chain acylcarnitine, and total carnitine in liver tissue from carnitine-infused cows but not in those infused with water. In muscle, acid-soluble carnitine, long-chain acylcarnitine, and total carnitine concentrations were increased by carnitine infusion and feed restriction without significant interaction. Feed restriction increased free carnitine concentrations in muscle from water-infused cows but not in carnitine-infused cows. Carnitine infusion increased the concentration of each milk carnitine fraction as well as milk carnitine output on d 8 to 9. On d 13 to 14, all carnitine fractions except short-chain acylcarnitine were increased in milk from water-infused, feed-restricted cows, whereas all fractions were increased in carnitine-infused, feed-restricted cows. Carnitine infusion increased total carnitine in plasma, liver, muscle, and milk during feed restriction, whereas feed restriction alone increased carnitine concentrations in muscle and milk but not in liver. Liver carnitine concentrations might limit hepatic fatty acid oxidation capacity in dairy cows during the periparturient period; therefore, supplemental l-carnitine might decrease liver lipid accumulation in periparturient cows.     

Development and characterization of antimicrobial poly(l-lactic acid) containing trans-2-hexenal trapped in cyclodextrins

Trans-2-hexenal, a naturally occurring plant volatile with antimicrobial capacity, was encapsulated into β-cyclodextrins (β-CDs), enzymatically modified starch, and shown effective to control main microorganisms causing food spoilage (Alternaria solani, Aspergillus niger, Botrytis cinerea, Colletotrichum acutatum, Penicillium sp). Loaded β-CDs were incorporated into a poly(l-lactic acid) (PLA) matrix by extrusion and casting, and yielded antimicrobial polymers made from natural resources. A masterbatch was used prior to sheet casting to improve the dispersion of the antimicrobial agent in the PLA matrix. However, this increased the number of extrusion processes for the material. The concentration of the antimicrobial compound in the polymers and its antimicrobial capacity against one food spoilage microorganism (A. solani) were measured during the different processing operations. Although the concentration of trans-2-hexenal was reduced by processing by about 70 and 99% compared to the loaded β-CDs, for the masterbatch and sheet, respectively, the polymers were still effective in reducing microbial growth. The changes of the polymer properties due to the addition of the antimicrobial agent were investigated, too. It was found that the mechanical and barrier properties of the PLA were changed (decreased by about half the tensile strength and elongation at break and nine-fold increased permeability) while the physical properties remained the same. Based on these results, the developed polymer may be a viable antimicrobial material for applications in food packaging.     

Oxidation of 6-O-arachidonoyl l-ascorbate microencapsulated with a polysaccharide by spray-drying

The oxidative stability at 37°C and 12% relative humidity of arachidonoyl moiety of 6-O-arachidonoyl l-ascorbate, which was synthesized through lipase-catalyzed condensation with l-ascorbic acid, was higher than that of unmodified arachidonic acid. Arachidonic acid and arachidonoyl ascorbate were microencapsulated with maltodextrin, gum arabic or a soluble soybean polysaccharide by spray-drying. The oxidation of arachidonic acid under the conditions was retarded by its microencapsulation with gum arabic or the soluble soybean polysaccharide. The oxidation of arachidonoyl moiety of the ascorbate encapsulated with gum arabic or the soluble soybean polysaccharide more slowly proceeded than unmodified or encapsulated arachidonic acid. The fractions of the unoxidized arachidonoyl moiety on day 29 were greater than 0.7. Thus, esterification of arachidonic acid with ascorbic acid and subsequent microencapsulation with gum arabic or the soluble soybean polysaccharide significantly improved its oxidative stability.     

Metabolic effects of abomasal L-carnitine infusion and feed restriction in lactating Holstein cows

l-Carnitine is required for mitochondrial fatty acid oxidation, but the effects of carnitine supplementation on nutrient metabolism during dry matter intake depression have not been determined in dairy cows. Studies in other species have revealed responses to l-carnitine that may be of specific benefit to dairy cows during the periparturient period. Eight lactating Holstein cows (132 ± 36 d in milk) were used in a replicated 4 × 4 Latin square experiment with 14-d periods. Treatments were factorial combinations of abomasal infusion of either water or l-carnitine (20 g/d; d 5 to 14) and either ad libitum or restricted intake (50% of previous 5-d dry matter intake; d 10 to 14) of a balanced lactation diet. Liver and muscle biopsies were obtained on d 14 of each period. Feed restriction induced negative balances of energy and metabolizable protein. In feed-restricted cows, carnitine infusion increased 3.5% fat-corrected milk yield compared with those infused with water. Total carnitine concentration in liver was increased in feed-restricted cows infused with carnitine but not in feed-restricted cows infused with water. Carnitine infusion stimulated in vitro oxidation of [1-¹⁴C] palmitate to acid-soluble products and decreased the proportion of [1-¹⁴C] palmitate that was converted to esterified products by liver slices. Feed-restricted cows infused with carnitine had lower liver total lipid concentration and tended to have decreased triglyceride accumulation compared with feed-restricted cows infused with water. Plasma nonesterified fatty acid concentration was not altered by carnitine infusion but was increased by feed restriction; serum β-hydroxybutyric acid was increased by carnitine infusion in feed-restricted cows. In cows fed for ad libitum intake, carnitine infusion affected β-hydroxybutyric acid, insulin, and urea N in serum, liver glycogen concentration, and in vitro alanine oxidation by liver slices, suggesting that hepatic and peripheral nutrient metabolism was influenced. l-Carnitine infusion effectively decreased liver lipid accumulation during feed restriction as a result of greater capacity for hepatic fatty acid oxidation. Further research examining dietary supplementation of l-carnitine during the periparturient period is warranted.     

Dietary L-carnitine affects periparturient nutrient metabolism and lactation in multiparous cows

The objectives of this study were to determine the effects of dietary l-carnitine supplementation on liver lipid accumulation, hepatic nutrient metabolism, and lactation in multiparous cows during the periparturient period. Cows were assigned to treatments at d −25 relative to expected calving date and remained on the experiment until 56 d in milk. Treatments were 4 amounts of supplemental dietary carnitine: control (0 g/d of l-carnitine; n = 14); low carnitine (LC, 6 g/d; n = 11); medium carnitine (MC, 50 g/d; n = 12); and high carnitine (HC, 100 g/d; n = 12). Carnitine was supplied by mixing a feed-grade carnitine supplement with 113.5 g of ground corn and 113.5 g of dried molasses, which was then fed twice daily as a topdress to achieve desired daily carnitine intakes. Carnitine supplementation began on d −14 relative to expected calving and continued until 21 d in milk. Liver and muscle carnitine concentrations were markedly increased by MC and HC treatments. Milk carnitine concentrations were elevated by all amounts of carnitine supplementation, but were greater for MC and HC than for LC during wk 2 of lactation. Dry matter intake and milk yield were decreased by the HC treatment. The MC and HC treatments increased milk fat concentration, although milk fat yield was unaffected. All carnitine treatments decreased liver total lipid and triacylglycerol accumulation on d 10 after calving. In addition, carnitine-supplemented cows had higher liver glycogen during early lactation. In general, carnitine supplementation increased in vitro palmitate β-oxidation by liver slices, with MC and HC treatments affecting in vitro palmitate metabolism more potently than did LC. In vitro conversion of Ala to glucose by liver slices was increased by carnitine supplementation independent of dose. The concentration of nonesterified fatty acids in serum was not affected by carnitine. As a result of greater hepatic fatty acid β-oxidation, plasma β-hydroxybutyric acid was higher for the MC and HC treatments. Serum insulin was greater for all carnitine treatments, although plasma glucose was unaffected. Plasma urea N was lower and plasma total protein was higher for the MC and HC treatments. By decreasing liver lipid accumulation and stimulating hepatic glucose output, carnitine supplementation might improve glucose status and diminish the risk of developing metabolic disorders during early lactation.     

Processing (blanching, boiling, steaming) effects on the content of glucosinolates and antioxidant-related parameters in cauliflower (Brassica oleracea L. ssp. botrytis)

Five different varieties of cauliflower (Brassica oleracea L. ssp. botrytis); two white (cv. ‘Aviso’, ‘Dania’), one purple (cv. ‘Grafitti’), one green (cv. ‘Emeraude’) and one romanesco/green pyramidal (cv. ‘Celio’) cultivar have been studied. All samples were thermally processed and the effects on the levels of glucosinolates (GLS), total phenols (TP), total monomeric anthocyanins (TMA), l-ascorbic acid (l-AA) and antioxidant capacities (FRAP and ORAC) were investigated. Processing methods applied were: blanching (3 min), boiling (10 min) and steaming (10 min). Total GLS were significantly (p < 0.05) affected by processing with the highest losses, 55 and 42% on average, occurring for boiled and blanched samples, respectively. Significant effects were also noted for steaming, but to a lesser extent, i.e. 19% average reduction. Antioxidant-related parameters were similarly affected with average losses of 27, 33, 36 and 46% in boiled cauliflower and 16, 21, 22 and 28% in blanched for TP, FRAP, l-AA and ORAC, respectively. Blanching and boiling reduced TMA in purple cauliflower by 38 and 53%, respectively. Steaming affected the antioxidant-related parameters the least for all cultivars. l-AA was significantly reduced by 14% in all cultivars by steaming. Some differences in behaviour between cultivars were noted, especially between white and coloured cultivars for TP, FRAP and l-AA, but also for some GLS. The main losses were caused by leaching into the processing water.     

L-selectin and chemotaxis throughout bone marrow granulocyte maturation in the bovine

Polymorphonuclear neutrophilic leukocytes (PMNL) play a pivotal role during inflammation. Bone marrow (BM) reserves are depleted as cells are released into circulation for recruitment to infection sites. Expression of L-selectin on the cell membrane allows neutrophils to roll along the activated endothelium. Whereas mechanisms leading to recruitment to infection sites are well established, expression of BM adhesion molecules in cows is limited. In this study, we assessed L-selectin expression and chemotactic response to zymosan-activated serum (ZAS) in bovine BM cells and in circulating neutrophils. Isolated blood PMNL and BM cells were used from 9 dairy cows, for quantifying L-selectin expression using flow cytometry, and from 12 dairy cows for chemotaxis studies. All granulocytic maturation stages expressed L-selectin. The percentage of cells fluorescing increased significantly in BM band and mature granulocytes and reached maximal expression on circulating neutrophils. Bone marrow band and segmented cells showed the highest L-selectin density. Chemotaxis through micropore filters in response to zymosan-activated fetal bovine serum was first observed in the myelocytic and metamyelocytic stages, and it increased with maturation and release into the blood stream. From these results, we conclude that L-selectin expression varies among stages of granulocytic maturation within the BM and differs from circulating PMNL. Further, BM cells are capable of migration starting at the metamyelocytic stage, and compared with BM cells, circulating neutrophils are more chemotactively active.     

The use of cyclic voltammetry to study the oxidation of l-5-methyltetrahydrofolate and its preservation by ascorbic acid

A cyclic voltammetry study of 1 mM l-5-methyltetrahydrofolate (l-5-MTHF) was performed in pH 5.5 Britton-Robinson buffer at room temperature to study the stability of l-5-MTHF alone and in combination with ascorbic acid (AA). The degradation of l-5-MTHF and AA over a period of 12 h both followed first order reaction kinetics. Using this technique, oxidation peaks of l-5-MTHF were identified at +0.17 and +1.18 V, and another oxidation peak appeared after 4 h under air at +0.89 V. Cyclic voltammetry and HPLC quantification enable us to confirm that l-5-MTHF can be highly preserved by the addition of an equimolar concentration of AA. This treatment was equivalent to a purge of nitrogen used to remove oxygen and thus minimise oxidation of l-5-MTHF when present in aqueous solutions. HPLC confirmed the fact that a full regeneration of oxidised l-5-MTHF occurred with the addition of sodium ascorbate, thus denoting that the redox character of l-5-MTHF can be controlled by the presence of reducing agents. Cyclic voltammetry proved to be a sensitive and accurate method for characterising l-5-MTHF oxidation and potential preservation with ascorbic acid. To our knowledge, this is the first study that has demonstrated the number of oxidation sites on l-5-MTHF.     

Mechanisms for antihypertensive effect of CocoanOX, a polyphenol-rich cocoa powder, in spontaneously hypertensive rats

We investigate the mechanisms involved in the long-term antihypertensive effect of a polyphenol-rich cocoa powder, named CocoanOX® (CCX), in spontaneously hypertensive rats (SHR). We have carried out two different batches of experiments. For the first batch of experiments, forty 3 week-old male SHR were randomly divided with ad libitum intake into four groups of 10 animals, that respectively received the following drinking fluids up to the 20th week of life (treatment period): tap water (control), CCX 100 mg/kg/day, CCX 200 mg/kg/day and CCX 400 mg/kg/day. Five 20 week-old rats of each group were sacrificed by decapitation. From the 20th to 24th week of life all the remaining animals were given tap water (follow-up period), and all of them were sacrificed at the end of the follow-up period. Plasma malondialdehyde (MDA), reduced glutathione in the liver, plasma and aorta angiotensin converting enzyme (ACE) activity and plasma angiotensin II were determined in all the sacrificed SHR that were included in this batch of experiments. Plasma MDA decreased and liver reduced glutathione increased in the 20 week-old CCX treated SHR. These effects were not observed in the rats that were sacrificed after the follow-up period. CCX treatment did not modify aorta ACE activity, but the activity of ACE and the levels of angiotensin II increased in the plasma of the SHR treated with the highest dose of CCX. ACE activity returned to basal values in the SHR that were sacrificed after the follow-up period. However, angiotensin II levels were slightly higher after withdrawal of CCX.For the second batch of experiments we used aorta rings obtained from untreated SHR, and we evaluated the relaxation caused by CCX in different aorta preparations. CCX relaxed the intact aorta preparations but this cocoa did not relax the endothelium-denuded aorta rings from the untreated SHR. l-NAME, but not indomethacin, inhibited the relaxation caused by CCX in the SHR aorta rings. We postulate that the antihypertensive effect of CCX might be mediated by an improvement of endothelial release of nitric oxide and by a reduction of oxidative stress. The inhibition of ACE could be implicated in the antihypertensive effect of CCX.     

Studies on photoyellowing of silk fibroin and alteration of its tyrosine content

The photoyellowing progress of silk fibroin and its influence factors under ultraviolet irradiation have been studied, which was conducted by combining different ultraviolet wavelengths, different ultraviolet irradiancies, and different irradiation times. The blue-ray whiteness after ultraviolet irradiation was tested to characterize the course of photoyellowing of silk fibroin. The result shows that the photoyellowing degree of silk fibroin varies significantly under ultraviolet irradiation of different wavelengths and with the increasing in ultraviolet irradiancy at 313-nm wavelength, the photoyellowing degree aggravates correspondingly, while the ultraviolet irradiancy at 340-nm wavelength has little obvious impact. Additionally, the photoyellowing degree of silk fibroin is positively correlated to ultraviolet irradiancy and irradiation time. To quantitatively analyze the alteration of tyrosine content during the photoyellowing of the silk fibroin, l-tyrosine standard curve Y = 8.14666X ? 0.88951 was established using HPLC with linear coefficient r = 0.99991 and precision degree coefficient of tyrosine analyses RSD₁ = 0.21%. Meanwhile, the tyrosine content of silk fibroin after acid hydrolysis was quantitatively analyzed by HPLC with precision degree coefficient RSD₂ = 1.12%. It can be seen that the change rate of the blue-ray whiteness of silk fibroin is positively proportional to the photodegradation rate of tyrosine, but the photodegradation rate of tyrosine ingredient is lower than the change rate of the blue-ray whiteness of silk fibroin.     

Mechanism for the inhibition of apple juice enzymatic browning by Palo Fierro (desert ironweed) honey extract and other natural compounds

Inhibition of Red Delicious apple juice browning and apple polyphenoloxidase (PPO) activity by four natural anti-browning agents [palo fierro honey extract (PFH), caffeic acid phenethyl ester (CAPE), l-cysteine (Cys), and 4-hexylresorcinol (4HR)] has been studied. Browning of apple juice was markedly reduced by 4HR, Cys, and PFH, however, little effect was observed with CAPE. PFH, CAPE, and 4HR showed high inhibition of apple juice PPO. When the inhibition mechanism of these compounds over partially purified apple PPO was studied using chlorogenic acid as substrate, PFH acted as a noncompetitive inhibitor of apple PPO, with K_i = αK = 0.8 g/L, and IC₅₀ ranging 1.1-1.7 g/L. Cys showed an inhibitory pattern which could not be fitted to any type of reversible inhibition (IC₅₀ 0.02-0.03 g/L), while CAPE showed low inhibitory activity, which could be due to co-precipitation processes. PFH could be considered as an effective natural compound to reduce apple juice browning.     

Preparation and properties of PLLA/PLCL fibres for potential use as a monofilament suture

Poly (l‐lactic acid) (PLLA) is one of the most promising biodegradable polymers that is being increasingly used for various biomedical applications. However, the literature recognises that for monofilament suture purposes, PLLA is too stiff and inflexible due to its greater glass transition temperature and crystallinity. In this paper, attempts have been made to modify the properties of PLLA by blending with poly (lactide‐co‐?‐caprolactone) (PLCL). In order to accomplish the goal, PLLA (90%) was combined with PLCL (10%) and monofilament fibres were obtained by dry–jet–wet spinning technique using chloroform and methanol as a solvent and nonsolvent, respectively. The as‐spun monofilaments were subsequently subjected to two‐stage hot drawing and heat setting process. The addition of PLCL to PLLA, in order to reduce the glass transition temperature and crystallinity, has shown a strong effect on the fibre properties. A crystallinity of 40% and glass transition temperature of 58°C were achieved for a draw ratio 9, whereas tenacity and modulus were 0.46 GPa and 6.7 GPa, respectively.     

Effect of dl-malic acid supplementation on feed intake, methane emissions, and performance of lactating dairy cows at pasture

The objective of this study was to determine the effect of dietary dl-malic acid (MA) supplementation on feed intake, methane (CH₄) emissions, and performance of mid lactation Holstein-Friesian cows at pasture. Twenty-four (6 primiparous and 18 multiparous) mid- to late-lactation cows (206 ± 65 d in milk) grazing a mixed-species grass sward were blocked on parity, days in milk, and pretrial milk yield, and randomly allocated within block to 1 of 2 dietary treatments offered twice daily at milking in 2 equal portions (6 kg/d in total): a control concentrate (0 g/d of MA) and a concentrate supplemented with MA (480 g/d of MA) over a 6-wk period. Cows were allowed a 3-wk acclimation period followed by a 5-d CH₄ measurement period. Enteric CH₄ emissions were estimated using the sulfur hexafluoride tracer gas technique, and herbage intake was measured using the n-alkane technique. Dietary supplementation with MA did not affect voluntary intake of herbage or total dry matter intake, body weight gain, milk yield, fat-corrected milk yield, or daily CH₄ production. These results suggest that there is little benefit to be gained from the dietary supplementation of dairy cows at pasture with MA at least within the inclusion rates used in this study.     

Using whey protein gel as a model food to study dielectric heating properties of salmon (Oncorhynchus gorbuscha) fillets

It is desirable to develop rapid commercial microwave and radio frequency sterilization processes to produce high quality shelf stable muscle foods, particularly aquatic foods. Whey protein gels containing d-ribose and salt were studied as a model food to determine heating patterns in salmon fillets during high temperature microwave sterilization processes. Dielectric constant (?′) and loss factor (?″) of whey protein gels with d-ribose (0.5 g/100 g, 1 g/100 g, and 1.5 g/100 g) at different salt contents (0, 0.1 g/100 g, 0.2 g/100 g, 0.3 g/100 g, 0.4 g/100 g, and 0.5 g/100 g) and frozen and thawed pink salmon (Oncorhynchus gorbuscha) fillets were determined over the frequency range of 27-1800 MHz at temperatures ranging from 20 to 120 °C. The dielectric properties of whey protein gels containing 1 g/100 g d-ribose and 0.2 g/100 g or 0.3 g/100 g salt closely matched the dielectric behavior of salmon fillets in both radio frequency (RF, 27 MHz) and microwave (MW, 915-1800 MHz) ranges. Altering the salt content had a greater impact on dielectric constant and loss factors at lower frequencies. These results suggest that whey protein gel may be a good model food for microwave sterilization process development, particularly for determining the locations of cold and hot spots in complex muscle foods.     

Formation of biogenic amines by Gram-negative rods isolated from fresh,spoiled, VP-packed and MAP-packed herring (<Emphasis Type="Italic">Clupea harengus</Emphasis>)

Bacterial strains (120) were isolated from fresh, spoiled, VP-packed and MAP-packed herring. Identified bacterial strains were investigated for their abilities to produce biogenic amines in histidine, lysine and ornithine decarboxylase broth by a rapid high-performance liquid chromatography (HPLC) method. The microflora of fresh herring was dominantly Pseudomonas (30%), Enterobacteriaceae (23.2%), Vibrio (13.3%) and Moraxella (13.3%) but, the microflora of herring stored in VP and MAP was dominated by species belonging to Vibrio (23.3%) and Moraxella (20%), which indicates that these packaging systems prevented the growth of Pseudomonas and Enterobacteriaceae. In a laboratory medium containing amino acid (histidine, ornithine and lysine), most of bacterial strains produced histamine, putrescine and cadaverine. The highest histidine decarboxylase activities were observed in Klebsiella oxytoca, Hafnia alvei and Proteus vulgaris which produced 396, 232 and 54 mg histamine/L, respectively in histidine-enriched broth. The accumulation of cadaverine by Klebsiella oxytoca and Hafnia alvei was 325 and 208 mg/l, respectively. All strains isolated produced putrescine in an ornithine-enriched broth, ranging from 3 to 249 mg/l. The production of putrescine by Klebsiella oxytoca and Hafnia alvei was 249 and 195 mg/l, respectively. Moraxella spp and Acinetobacter spp did not produce histamine which indicates they did not have histidine decarboxylase activity.     

Optimization of natural fermentative medium for selenium-enriched yeast by d-optimal mixture design

Natural fermentative medium for selenium-enriched yeast (Saccharomyces cerevisiae) culture was investigated using response surface methodology (RSM). The medium with a concentration of 15 μg/mL Na₂SeO₃, contained various ratios of juices from germinated brown rice (0.40 ∼ 0.80, 12 Brix), beerwort (0.10 ∼ 0.50, 12 Brix) and soybean sprout (0.10 ∼ 0.50, 12 Brix), which were optimized by applying d-optimal mixture design (DMD). The effects of their ratios on biomass yield and total selenium (Se) yield were analyzed. The results showed that when the mixed ratio of the components was 4:4:2 (v:v:v), the maximum value of biomass yield and total Se yield were 8.5 g/L and 3.53 mg/L, respectively. Verification experimental trials were performed for validating the models, and it indicated that the above mixture of these natural materials can be used as proper medium for the growth of selenium-enriched yeast and accumulation of Se.     

Myosin filament depolymerizes in a low ionic strength solution containing l-histidine

Myosin, one of the major myofibrillar proteins, forms a filamentous polymer and is insoluble in physiological and low ionic strength solutions. We have shown that myosin is soluble in a low ionic strength solution containing l-histidine. In this study, to clarify the role of l-histidine in the solubilization of myosin, we investigated effects of l-histidine on the filament formation and the morphology of myosin at a low ionic strength. In the presence of l-histidine, myosin formed a filamentous polymer in a physiological ionic strength solution and dispersed in a low ionic strength solution. Transmission electron microscopy showed that light meromyosin (LMM), the rod region of myosin, in a low ionic strength solution containing l-histidine was longer than that in a high ionic strength solution without l-histidine. l-histidine causes the elongation of LMM region of myosin contributing to the weakening of the myosin filament and the dissociation of myosin in a low ionic strength solution.     

Evaluation of l-ascorbic acid oxidation on SH concentration in soy-wheat composite dough during resting period

The effect of l-ascorbic acid (l-AA) on free sulfhydryl concentration (SH) was evaluated in soy-wheat composite dough from 100-500 (g/kg) soy flour substitution for wheat flour. Raw soy flour (RSF) and physically modified soy flours (PMSF1 and PMSF2) were used for the preparation of the composite dough with wheat flour. The two physically modified soy flours were prepared by steam flushing (PMSF2) and water boiling (PMSF1) of raw soy beans before flour preparation. Using a timer, dough blends were manually mixed (at approximately 60 rpm) to dough development time after which, dough was sampled for the estimation of free SH groups. l-AA (0.05% w/w) was mixed with the dough after dough development and the dough was sampled after 1 h of resting the dough. The results showed that l-AA (0.05% w/w) acted as a reducing agent by increasing SH levels in all soy-wheat dough blends (P<0.05). After 1 h of resting, soy-wheat composite dough without l-AA had lower concentrations of SH than that with l-AA. A positive correlation was shown between soy flour concentrations and SH concentration before and after dough resting. A negative correlation existed between l-AA consumption and SH concentration for RSF-wheat, PMSF1-wheat and PMSF2-wheat doughs. The results indicated that soy flour weakened wheat flour dough by increasing SH concentration and that l-AA could have a synergistic effect on the reduction of gluten proteins and thus weakening the dough.