Effect of gamma radiation on levels of α-tocopherol in red meats and turkey

The effect of low dose ionizing radiation on free α-tocopherol levels in beef, pork and lamb longissimus dorsi muscle and on turkey leg and breast muscle were determined. The samples were irradiated in air with a ¹³⁷Cs source at eight dose levels between 0 and 9.4 kGy at 5 °C. Irradiation resulted in a significant decrease in α-tocopherol levels in all of the meats studied. There were no statistically significant differences in the rate of loss of tocopherol due to species, with the exception of turkey breast. The rate of loss of tocopherol in turkey breast tissue was greater than the other meats. The information obtained in this study may be of use for ‘chemiclearance’ purposes since the relative effects due to species variation were examined.     

The effects of dietary oregano essential oil and α-tocopheryl acetate on lipid oxidation in raw and cooked turkey during refrigerated storage

The effects of dietary oregano essential oil and α-tocopheryl acetate supplementation on the susceptibility of raw and cooked turkey breast and thigh meat to lipid oxidation during refrigerated storage for 9 days were examined. Thirty 12-week-old turkeys were divided into five groups and fed a basal diet containing 30 mg α-tocopheryl acetate kg(-1) feed as control, or basal diet plus 200 mg α-tocopheryl acetate kg(-1), or basal diet plus 100 mg oregano oil kg(-1), or basal diet plus 200 mg oregano oil kg(-1), or basal diet plus 100 mg oregano oil and 100 mg α-tocopheryl acetate kg(-1), for 4 weeks prior to slaughter. Lipid oxidation was assessed by monitoring malondialdehyde formation in raw and cooked meat at 0, 3, 6 and 9 days of refrigerated storage, through use of a third-order derivative spectrophotometric method. Results showed that all dietary treatments significantly (P<0.05) increased the stability of both raw and cooked turkey meat to lipid oxidation compared with the control. Oregano oil at 200 mg kg(-1) was significantly (P<0.05) more effective in delaying lipid oxidation compared to the level of 100 mg kg(-1), equivalent to α-tocopheryl acetate at 200 mg kg(-1), but inferior (P<0.05) to oregano oil plus α-tocopheryl acetate at 100 mg kg(-1) each, which in turn was superior (P<0.05) to all dietary treatments, indicating a synergistic effect. Thigh muscle was more susceptible to oxidation compared with breast muscle in all treatments, although it contained α-tocopherol at significantly (P<0.05) higher levels.     

Effect of dietary olive leaves and/or α-tocopheryl acetate supplementation on microbial growth and lipid oxidation of turkey breast fillets during refrigerated storage

Thirty turkeys were allocated to five groups of six birds each. One group that served as control was fed a basal diet, while the others were fed diets supplemented with olive leaves at 5 or 10 g/kg, or α-tocopheryl acetate at 150 or 300 mg/kg. Following slaughter, fillets from breast were stored at 4 °C in the dark for 12 days, and lipid oxidation and microbial growth were assessed. Results showed that the incorporation of olive leaves in turkey diets increased (P < 0.05) the oxidative stability of raw breast fillets during refrigerated storage. Dietary olive leaves at 10 g/kg were more effective (P < 0.05) in inhibiting lipid oxidation compared to 5 g/kg, but inferior to the supplementation of 300 mg α-tocopheryl acetate/kg. In turn, α-tocopheryl acetate supplementation at 150 mg/kg was equal to olive leaves at 5 g/kg but inferior to olive leaves at 10 g/kg. Total viable counts, lactic acid bacteria, Enterobacteriaceae and psychrotrophic bacteria counts were all increased (P < 0.05) in breast fillets of all groups throughout the refrigerated storage. Diet supplementation with α-tocopheryl acetate had no effect on the bacterial counts recorded in the control group, but diet supplementation with olive leaves resulted in decrease (P < 0.05) of all bacterial counts at day 2 of storage and thereafter; during this period, olive leaves at the level of 10 g/kg were more effective in inhibiting bacterial growth compared to the level of 5 g/kg.     

Activated effect of lignin on α-amylase

This paper reports a new kind of activator of α-amylase, lignin, which can greatly increase α-amylase activity. The promoted ratio of lignin is even much higher than that of chloride ion, the traditional activator of α-amylase. Further experimental results reveal that lignin may interact with α-amylase to form a 1:1 complex with a binding constant of 4.47 × 10⁵ M⁻¹. The binding is spontaneous and lignin/α-amylase complex formation is an exothermal reaction. Hydrogen bonding plays a key role and non-radiation energy transfers from α-amylase to lignin in the binding process. Lignin, combining with α-amylase, conforms to a first-order exponential decay function. The formation of the lignin/α-amylase complex results in the reduction of α-helical content from 57.7% to 53.9%, the increase of the polarity around tryptophan residues, the decrease of the hydrophobicity, and the enlargement of protein granule volume. This work will give a deeper insight into lignin as a kind of dietary fibre, known as an important food functional factor. Furthermore, it also contributes to the exploration of an activator of α-amylase, used in the food industry.     

Influence of α-tocopherol on physicochemical properties of chitosan-based films

Chitosan has been exploited as a material for the development of edible films, and additionally can be used as a carrier of functional compounds such as α-tocopherol. The aim of this work was to evaluate the effects of the incorporation of α-tocopherol in chitosan-based films. FTIR and thermal analyses were performed and showed that the incorporation of α-tocopherol affects the chemical structure of chitosan-based films with the establishment of new chemical bonds and the decrease of crystallinity. Results also showed that the increase of α-tocopherol concentration promotes a decrease of water content (from 12.6 to 11.4%) of the films. The addition of α-tocopherol to chitosan films leads to a significant reduction (p < 0.05) of tensile strength from 34.06 to 16.24 MPa, and elongation-at-break from 53.84 to 23.12%. Film opacity values (ranging from 4.74 to 7.83%) increased when α-tocopherol was incorporated into the film. Antioxidant capacity of chitosan-based films was evaluated and was enhanced when α-tocopherol was present in the film matrix. Results showed that α-tocopherol can be successfully added to the chitosan films enhancing the final quality and shelf-life extension of food products.     

Probabilistic models for the prediction of target growth interfaces of Listeria monocytogenes on ham and turkey breast products

Abstract: This study developed growth/no growth models for predicting growth boundaries of Listeria monocytogenes on ready‐to‐eat cured ham and uncured turkey breast slices as a function of lactic acid concentration (0% to 4%), dipping time (0 to 4 min), and storage temperature (4 to 10 °C). A 10‐strain composite of L. monocytogenes was inoculated (2 to 3 log CFU/cm²) on slices, followed by dipping into lactic acid and storage in vacuum packages for up to 30 d. Total bacterial (tryptic soy agar plus 0.6% yeast extract) and L. monocytogenes (PALCAM agar) populations were determined on day 0 and at the endpoint of storage. The combinations of parameters that allowed increases in cell counts of L. monocytogenes of at least l log CFU/cm² were assigned the value of 1, while those limiting growth to <1 log CFU/cm² were given the value of 0. The binary data were used in logistic regression analysis for development of models to predict boundaries between growth and no growth of the pathogen at desired probabilities. Indices of model performance and validation with limited available data indicated that the models developed had acceptable goodness of fit. Thus, the described procedures using bacterial growth data from studies with food products may be appropriate in developing growth/no growth models to predict growth and to select lactic acid concentrations and dipping times for control of L. monocytogenes. Practical Application: The models developed in this study may be useful in selecting lactic acid concentrations and dipping times to control growth of Listeria monocytogenes on cured ham and uncured turkey breast during product storage, and in determining probabilities of growth under selected conditions. The modeling procedures followed may also be used for application in model development for other products, conditions, or pathogens.     

Effects of dietary α-lipoic acid on glycolysis of postmortem muscle

The effects of dietary α-lipoic acid (α-LA) on the pH value, AMP-activated protein kinase (AMPK) activation, and the activities of glycogen phosphorylase and pyruvate kinase in postmortem muscle were investigated. Eighteen C57BL/6J mice were fed diets containing 0%, 0.5%, and 1.0% α-LA. At the end of 2-week feeding trial, the mice were killed and longissimus muscles were sampled at 0-, 1-, and 24-h postmortem for pH determination and enzyme assay. The results showed that dietary α-LA treatment significantly slowed down the decrease of pH values in postmortem muscle. The ultimate pH values in postmortem muscle of mice receiving 0.5% and 1.0% α-LA treatments were 6.40 and 6.63, respectively, significantly higher than that (6.21) of no α-LA treatment (p<0.05). AMPK was activated at the early postmortem stage. Dietary α-LA can suppress the activation of AMPK in postmortem muscle. At 1- and 24-h postmortem, activities of AMPK were much lower in postmortem muscle of mice receiving 0.5% and 1.0% α-LA treatments than that with no α-LA treatment. Between these two dietary α-LA treatments, however, no difference in AMPK activity was observed, indicating that 0.5% dietary α-LA is enough to suppress AMPK in postmortem muscle. Similar to AMPK, glycogen phosphorylase activity was higher in the treatment without dietary α-LA than those with 0.5% and 1.0% dietary α-LA supplements. No difference in the activity of glycogen phosphorylase was observed between the 0.5% and 1.0% dietary α-LA treatments. Dietary α-LA had no significant influence on the activity of pyruvate kinase in postmortem muscle. All these results indicate that AMPK plays a role in glycolysis in postmortem muscle. Dietary α-LA supplementation can suppress the activation of AMPK in postmortem muscle, down-regulate the activity of glycogen phosphorylase, resulting in a higher ultimate pH values in postmortem muscle. Therefore, dietary α-LA supplementation is a potential way to reduce the incidence of pale, soft, exudative (PSE) meat.     

Effects of high hydrostatic pressure on the structure of bovine α-lactalbumin

The effects of high hydrostatic pressure (HHP) processing (at 200 to 600 MPa, 25 to 55°C, and from 5 to 15 min) on some structural properties of α-lactalbumin was studied in a pH range of 3.0 to 9.0. The range of HHP processes produced a variety of molten globules with differences in their surface hydrophobicity and secondary and tertiary structures. At pH values of 3 and 5, there was a decrease in the α-helix content concomitant with an increase in β-strand content as the pressure increased. No changes in molecular size due to HHP-induced aggregation were detected by sodium dodecyl sulfate-PAGE. All samples showed higher thermostability as the severity of the treatment increased, indicating the formation of a less labile structure related to the HHP treatment.     

Ultrasonic effect on physicochemical and functional properties of α-lactalbumin

Ultrasound is the sound whose frequency is too high for humans to hear which is within the frequency range of 20 Hz-20 kHz, and the frequency of ultrasound is above 20 kHz. The aim of this study was to observe the effect of ultrasound and sonication on α-lactalbumin (α-LA) with a view to improving its physicochemical and functional properties. In this work both low-intensity ultrasound (500 kHz bath) and the high-intensity ultrasound (20 kHz probe and 40 kHz bath) were used. Ten per cent wt (g g⁻¹ dry matter) protein model suspensions of α-lactalbumin (α-LA) were treated with ultrasound probe (20 kHz for 15 and 30 min) and ultrasound baths (40 kHz and 500 kHz for 15 and 30 min).Changes in pH values, electrical conductivity, solubility measurements, foaming properties, as well as rheological and freezing-thawing properties have been examined. The protein fractions of α-lactalbumin were analyzed before and after ultrasound treatment by SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis).The result showed that pH did not change significantly upon ultrasound however conductivities increased significantly after 20 kHz sonication. Electrical conductivity decreased significantly for ultrasound treatments in baths at 40 kHz and 500 kHz for all samples. Solubility increased significantly for all samples at 20 kHz. Foam capacities and foam stabilities were improved after ultrasound treatments for both 20 kHz and 40 kHz treatments. Foaming properties were not improved for protein model suspensions for 500 kHz treatments. The molecular weight of the protein decreased significantly after ultrasound treatments both using a 20 kHz probe and 40 kHz bath. The flow behaviour of α-lactalbumin was observed to be shear-thickening after all treatments. Apparent viscosity data calculated with power law equation (R² = 0.983-0.999) have not been changed significantly after all treatments. A remarkable decrease of initial freezing point was obtained after 20 kHz treatments.     

Effect of high-pressure treatment on denaturation of bovine β-lactoglobulin and α-lactalbumin

The effect of high-pressure treatment on denaturation of β-lactoglobulin and α-lactalbumin in skimmed milk, whey, and phosphate buffer was studied over a pressure range of 450–700 MPa at 20 °C. The degree of protein denaturation was measured by the loss of reactivity with their specific antibodies using radial immunodiffusion. The denaturation of β-lactoglobulin increased with the increase of pressure and holding time. Denaturation rate constants of β-lactoglobulin were higher when the protein was treated in skimmed milk than in whey, and in both media higher than in buffer, indicating that the stability of the protein depends on the treatment media. α-Lactalbumin is much more baroresistant than β-lactoglobulin as a low level of denaturation was obtained at all treatments assayed. Denaturation of β-lactoglobulin in the three media was found to follow a reaction order of n = 1.5. A linear relationship was obtained between the logarithm of the rate constants and pressure over the pressure range studied. Activation volumes obtained for the protein treated in milk, whey, and buffer were −17.7 ± 0.5, −24.8 ± 0.4, and −18.9 ± 0.8 mL/mol, respectively, which indicate that under pressure, reactions of volume decrease of β-lactoglobulin are favoured. Kinetic parameters obtained in this work allow calculating the pressure-induced denaturation of β-lactoglobulin on the basis of pressure and holding times applied.     

Activity of diastase α-amylase immobilized on polyanilines (PANIs)

Starch hydrolysing enzyme α-amylase (EC 3.2.1.1) was immobilized by physical adsorption and covalent binding onto chemically synthesised polymer, polyanilines (PANIs) in two different forms, emeraldine salt and emeraldine base powder. The immobilization efficiency was affected by the pH of the immobilization medium, contact time and amount of enzyme. The kinetic parameters, reusability and storage stability of the enzyme were studied under free and immobilized condition at optimum pH and temperature. The immobilized enzyme showed enhanced storage stability over a period of 6 months, while free enzyme in solution lost all of its activity within a period of 8 days. Reusability of the enzyme was improved by immobilization. The K_m values for starch hydrolysis were found to be high for the immobilized enzymes.     

Inhibitory effects of α-cyano-4-hydroxycinnamic acid on the activity of mushroom tyrosinase

The effects of α-cyano-4-hydroxycinnamic acid (HCCA) on the activity of mushroom tyrosinase have been studied. Results showed that HCCA could inhibit both the monophenolase activity and diphenolase activity of mushroom tyrosinase. For the monophenolase activity, the lag phase was obviously lengthened, and the steady-state activity of the enzyme decreased sharply. When the concentration of HCCA reached to 80 μM, the lag time was lengthened from 20 s to 150 s and the steady-state activity was lost by about 75%. The IC₅₀ value was estimated to be 48 μM. For the diphenolase activity, the inhibitory effect of HCCA was also dose-dependent and the IC₅₀ value was estimated to be 2.17 mM. The kinetic analyses showed that the inhibition of HCCA on the diphenolase activity was reversible and competitive with the inhibition constants (K_I) determined to be 1.24 mM.     

Effects of rendering and α-tocopherol addition on the oxidative stability of horse fat

Food Science and Biotechnology - Oxidative stability of horse fat rendered at 70&nbsp;°C, − 0.1&nbsp;MPa under vacuum and 110&nbsp;°C, 0.1&nbsp;MPa from horse...     

Reaction kinetics study of α-amylase in the hydrolysis of starch size on cotton fabrics

A study of tension surging and of the properties of the resultant yarns is reported. Tension profiles are discussed and assigned to three modes of operation, namely, pre-surging, surging, and post-surging. The critical conditions for these three modes and the wavelengths and amplitude of tension surging are investigated. The insertion of twist is examined, and it is shown that, not only is the surging mode unstable, hut there is also a higher-frequency instability in the post-surging mode. On the basis of the results obtained from routine tests for textured yarns, it is confirmed that the quality of the yarns resulting from both surging and post-surging modes is not acceptable.     

Role of reverse micelles on lipid oxidation in bulk oils: impact of phospholipids on antioxidant activity of α-tocopherol and Trolox

Phospholipids self-assemble in bulk oils to form structures such as reverse micelles that can alter the microenvironment where chemical degradation reactions occur, such as lipid oxidation. In this study, we examined the influence of phospholipid reverse micelles on the activity of non-polar (α-tocopherol) and polar (Trolox) antioxidants in stripped soybean oil (SSO). Reverse micelles were formed by adding 1000 μM 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) to SSO. The addition of DOPC reverse micelles had a prooxidant effect, shortening the lag phase of SSO at 55 °C. DOPC improved the activity of low α-tocopherol or Trolox concentrations (10 μM) but decreased the activity of high concentrations (100 μM). Hydrophilic Trolox had better antioxidant activity than hydrophobic α-tocopherol. Fluorescence steady state and lifetime decay studies suggests that differences in the antioxidant activity of Trolox and α-tocopherol could be due to differences in their physical location in DOPC reverse micelles. These results will improve our understanding and control of lipid oxidation in bulk oils.     

Effect of ferulic acid and α-tocopherol antioxidants on properties of sodium caseinate edible films

Edible films, based on sodium caseinate containing three different concentrations of ferulic acid or α-tocopherol (20, 40 and 60 mg/g sodium caseinate), were obtained in order to evaluate the effect of these compounds on properties of the caseinate matrices. Special emphasis was placed on their effect on the films’ oxygen barrier properties, which are decisive in the prevention of the oxidation of foods containing lipids. Films were characterized as to their tensile, optical and surface properties as well as their barrier properties to water vapor, oxygen and aroma compounds (n-hexanal and n-hexanol). Ferulic acid was more efficient at reducing oxygen and n-hexanal permeability than α-tocopherol. Although ferulic acid slightly increased the stiffness of films at low concentration, in general, both antioxidants slightly reduce mechanical resistance, water vapor permeability, gloss and transparency of the films.     

Effect of additives on mesophilic α-amylase and its application in the desizing of cotton fabrics

An investigation was carried out on thermal stability of α-amylase. The influence of various additives (calcium acetate, sodium lactate, L-histidine, and water-soluble chitosan) on the stability of α-amylase was studied. Results showed the inactivation behavior of α-amylase with or without additives all followed the first-order kinetics. All additives (Ca2+, sodium lactate, L-histidine, and water-soluble chitosan) displayed good stabilizing effect on α-amylase lower than 80 °C, and only water-soluble chitosan had an efficient stabilizing effect on α-amylase when the treatment temperature exceeds 80 °C. All additives improved the catalytic activity of α-amylase at 70–90 °C, and the appearance of water-soluble chitosan increased the catalytic activity of α-amylase at 90 °C sharply. A desizing ratio of 68.42% was obtained by treating the cotton fabrics in the buffer solution at 100 °C without α-amylase. To obtain a desizing ratio exceed 95% when fabrics were treated at 100 °C for 10 min, the addition of water-soluble chitosan saves 2/3 α-amylase dosage. Moreover, water-soluble chitosan showed a further improvement in desizing effect than the additive of calcium acetate.     

Effect of hydrophilic organic seed aerosols on secondary organic aerosol formation from ozonolysis of α-pinene

Gas-particle partitioning theory is widely used in atmospheric models to predict organic aerosol loadings. This theory predicts that secondary organic aerosol (SOA) yield of an oxidized volatile organic compound product will increase as the mass loading of preexisting organic aerosol increases. In a previous work, we showed that the presence of model hydrophobic primary organic aerosol (POA) had no detectable effect on the SOA yields from ozonolysis of α-pinene, suggesting that the condensing SOA compounds form a separate phase from the preexisting POA. However, a substantial faction of atmospheric aerosol is composed of polar, hydrophilic organic compounds. In this work, we investigate the effects of model hydrophilic organic aerosol (OA) species such as fulvic acid, adipic acid, and citric acid on the gas-particle partitioning of SOA from α-pinene ozonolysis. The results show that only citric acid seed significantly enhances the absorption of α-pinene SOA into the particle-phase. The other two seed particles have a negligible effect on the α-pinene SOA yields, suggesting that α-pinene SOA forms a well-mixed organic aerosol phase with citric acid and a separate phase with adipic acid and fulvic acid. This finding highlights the need to improve the thermodynamics treatment of organics in current aerosol models that simply lump all hydrophilic organic species into a single phase, thereby potentially introducing an erroneous sensitivity of SOA mass to emitted OA species.