EFFECTS OF LOW CONCENTRATIONS OF H2O2 ON LIPID OXIDATION AND OF STORAGE AND pH ON NONHEME IRON CONTENT OF RAW BEEF MUSCLE

Ground beef samples were prepared from semimembranosus muscles, and beef muscle residue devoid of heme pigments was prepared by repeated washing of the ground muscle with distilled-deionized water. When ground muscle, or muscle residue samples treated with metmyoglobin-H₂O₂ (4 mg metmyoglobin/g muscle residue; 1:0.1 to 1:1 for molar ratio of metmyoglobin to H₂O²) were stored at 4°C for 0 or 6 days, no changes in nonheme iron content were observed. Similarly, nonheme iron content of stored samples was not affected by pH (5.5, 6.0 or 6.5). While metmyoglobin-H₂O² added to water-extracted beef muscle residue catalyzed the oxidation of the indigenous lipids, treatment of the residue with H₂O² alone had no effect on the oxidation.     

The Binding of H2O2-Generated Fe(III) to Bifidobacterium thermophilum Depends on the Method of its Production

ABSTRACT: Fe(OH)₃ was produced from Fe(II) and H₂O₂ by methods associated with high and low free radical activity. More Fe(OH)₃ became bound to Bifidobacterium thermophilum when the former type of method was used, and protoplasting experiments indicated that binding to both the cell walls and membranes was enhanced. Binding to cell walls was instantaneous, whilst that by the membranes increased with time using both methods. Al(III), a lipid peroxidation enhancer, increased Fe(OH)₃ binding by membranes only. It was concluded that B. thermophilum is able to abate increased activity of free radicals not only by scavenging them, but also by removing iron from their environment.     

Reaction characteristics of a tooth-bleaching agent containing H2O2 and NaF: in vitro study of crystal structure change in treated hydroxyapatite and chemical states of incorporated fluorine

This in vitro study was performed to elucidate the reaction mechanism of sodium fluoride (NaF), which is added to tooth-bleaching agents to lessen the adverse effect of hydrogen peroxide (H₂O₂) on teeth. Both hydroxyapatite (HAP) and dihydrated dicalcium phosphate (DCPD), model substances for dental hard tissues, dissolved easily in a simple H₂O₂ solution. In the H₂O₂/NaF solutions, however, fluorine compounds that could not be identified by X-ray diffraction (XRD) due to the smallness of the products were formed on the surface of the HAP. X-ray photoelectron spectroscopy (XPS) studies demonstrated that fluoridated hydroxyapatite (FHAP) was formed on HAP, and that calcium fluoride (CaF₂) formation was accelerated by increasing the concentrations of fluorine and H₂O₂ along with the partial dissolution of HAP. In H₂O₂/NaF solution, DCPD also transformed easily to FHAP and CaF₂, which are favorable to the remineralization process on the tooth surface. Thus, the mechanism of NaF was elucidated, and its use together with H₂O₂ for tooth bleaching was proved to be effective. Methodologically, the XPS two-dimensional plot made it possible for the first time to directly estimate the ratio of FHAP and CaF₂ in the reaction products, in contrast to the conventional wet-analytical method, which is simply based on the difference in solubility of the two components.     

Reaction characteristics of a tooth-bleaching agent containing H2O2 and NaF: in vitro study of crystal structure change in treated hydroxyapatite and chemical states of incorporated fluorine

This in vitro study was performed to elucidate the reaction mechanism of sodium fluoride (NaF), which is added to tooth-bleaching agents to lessen the adverse effect of hydrogen peroxide (H₂O₂) on teeth. Both hydroxyapatite (HAP) and dihydrated dicalcium phosphate (DCPD), model substances for dental hard tissues, dissolved easily in a simple H₂O₂ solution. In the H₂O₂/NaF solutions, however, fluorine compounds that could not be identified by X-ray diffraction (XRD) due to the smallness of the products were formed on the surface of the HAP. X-ray photoelectron spectroscopy (XPS) studies demonstrated that fluoridated hydroxyapatite (FHAP) was formed on HAP, and that calcium fluoride (CaF₂) formation was accelerated by increasing the concentrations of fluorine and H₂O₂ along with the partial dissolution of HAP. In H₂O₂/NaF solution, DCPD also transformed easily to FHAP and CaF₂, which are favorable to the remineralization process on the tooth surface. Thus, the mechanism of NaF was elucidated, and its use together with H₂O₂ for tooth bleaching was proved to be effective. Methodologically, the XPS two-dimensional plot made it possible for the first time to directly estimate the ratio of FHAP and CaF₂ in the reaction products, in contrast to the conventional wet-analytical method, which is simply based on the difference in solubility of the two components.     

Stability and Photochemistry of Vitamin D2 in Model System

Oxidation of vitamin D₂ in a model system of 12% water and 88% acetone in the presence of 15 ppm riboflavin under light and dark was studied by measuring the depleted headspace oxygen. Riboflavin accelerated the oxidation of vitamin D₂ by singlet oxygen under light, but did not affect the vitamin D₂ oxidation under dark. The effect of 0 and 15 ppm riboflavin on the stability of vitamin D₂ during storage at 25 and 60°C was studied by measuring the contents of vitamin D₂ during 48h. Results indicated that photosensitized singlet oxygen oxidation of vitamin D₂ under light was temperature-independent, and triplet oxygen oxidation of vitamin D₂ both under light and in the dark was temperature-dependent.     

PRODUCTION OF CO2 AND C2H4 AFTER GAMMA IRRADIATION OF STRAWBERRY FRUIT

Strawberry fruit (Fragaria ananassa, Duch. cv ‘Kent’) were irradiated at doses from 0 to 4 kGy and stored at 10°C to verify whether irradiation at very low doses could delay postharvest ripening while causing minimal damage to the tissues. CO₂ and C₂H₄ production were used as stress indicator. Anthocyanins and titratable acidity were measured as maturity parameters. CO₂ and C₂H₄ production increased six hours after irradiation. The increase in CO₂ production was proportional to the dose of irradiation and was highest at 4 kGy. Maximum C₂H₄ production was reached at 1 kGy. The different response of CO₂ and C₂H₄ production to irradiation suggests that the membrane system supporting C₂H₄ production was more sensitive to gamma rays than mitochondrial CO₂ production. Irradiation at 0.3 kGy slightly delayed color development in the fruit. Overall, the results indicated that it may be possible to use irradiation at a low dose to delay ripening while causing only minimal tissue damage.     

Dynamic Changes of Headspace Gases in CO2 and N2 Packaged Fresh Beef

Two independent experiments were conducted to examine the effects of initial packaging/product conditions and storage conditions on in-package headspace pressure changes for modified atmosphere packaged beef during 12 hr storage. Headspace-to-meat volume ratio 1.8 to 5.9, surface area 200--800 cm², sample volume 0.22–0.75L, storage at 3–13°C and initial gas composition 20–100% CO₂ balanced with N₂ were studied. Headspace-to-meat volume ratio was the most important packaging parameter, but surface area and meat volume also affected headspace CO₂ changes. Decreased storage temperature reduced CO₂ concentration remaining in headspace. Higher initial CO₂ concentration resulted in greater concentration changes.     

KCI, CaCI2, Na+ Binding, and Salt Taste of Gum Systems

Aqueous nonionic (0.3% w/v) and ionic (0.1% and 0.3% w/v) gum systems containing NaCl, or equal weights of NaCl plus KCl, or NaCl plus CaCl, were examined. At equivalent molar concentrations of added ions, ²³Na NMR transverse relaxation rates (R₂, set^?1) showed an increase in average Na⁺ mobility with the addition of K⁺ or Ca²⁺ to ionic gum systems. Correspondingly, salt taste increased with addition of KCl as determined by Decision Boundary modeling of subject identification data. Viscosity did not affect saltiness. Na⁺ was free to induce salt taste when K⁺ was bound to the gum. Enhancement of salt taste by KCl is due, in part, to competitive binding of Na⁺ and K⁺ in a system.     

Characterisation of soybean glycinin and β-conglycinin fractionated by using MgCl2 instead of CaCl2

A simple two step precipitation method was used to investigate the effect of MgCl₂ instead of CaCl₂ on fractionation of soybean glycinin and β-conglycinin. Compositional and physicochemical properties of the resulting protein fractions were characterised. The optimised procedure, in terms of protein yield, purity, phytate content and physicochemical properties, was obtained when the addition of 5 m m MgCl₂ was used. After application of 5 m m MgCl₂, the phytate content of the glycinin-rich and β-conglycinin-rich fractions was about 0.4% and 1.3%, respectively, but the addition of 5 m m CaCl₂ increased the phytate content of the glycinin-rich fraction to 1.25% and decreased that of β-conglycinin-rich fraction to 0.67%. Low phytate protein product was suitable for use in infant formula and acidic food. The solubility of the glycinin-rich fractions with MgCl₂ was significantly higher than that with CaCl₂ at pH < 4.5. Application of MgCl₂ improved thermal stability of the β-conglycinin-rich fraction.     

Effects of Brine and CO2 Chilling Systems on Hot-Processed Vacuum-Packaged Pork

Quality, packaging and sensory attributes were evaluated for hot-processed boneless loin segments (blade-end and sirloin-end) and Boston shoulders that were brine, CO² or conventionally chilled. The only pH or temperature differences (P < 0.05) among processing treatments occurred at 3 hr postmortem. Boneless loin segments and Boston shoulders that were hot processed and CO²-chilled had higher (P < 0.05) purge values than their conventionally processed counterparts. No significant differences were found among treatments for sensory traits or shear values. Overall, boneless loins and Boston shoulders from hot-processed carcasses that were brine or CO²-chilled were similar in dimensional measurements and sensory traits.     

SPECIFICITY OF THE FERRIC-H2SO4 REAGENT FOR ALGINATES

SUMMARY— Alginate in foods was isolated from papain digests of the samples as the insoluble calcium salt. dispersed by sodium hexametaphosphate and a 1- to 5-ml aliquot of the dispersion 50–250 μg of sodium alginate) dried at 100°C. Heating of the anhydrous sample in the presence of the ferric-H₂SO₄ reagent for 12 min at 60°C produced a pink color with maximum absorption at 490–515 mμ and maximum density after aging for 90 min at 29±1°C. Under these conditions, proteins, amino acids (except tryptophane), other carbohydrates, vitamins. food additives and incipients did not interfere. The presence of water in the medium rendered the reaction nonspecific and increasing the temperature above 60°C or heating for longer periods at lower temperatures resulted in color formation by other polyuronides, especially pectin and pectic acid. Recoveries of alginate from several products were good: Milk, 94–98%; ice cream, 93.5–98%; pasteurized process cheese spread. 92.6-95%; chocolate milk, 92.4-95%; dietetic foods, 90-97.2%.     

Residual NO−3 NO−2, carbonyl and TBA values of Turkish soudjouk manufactured by adding different starter cultures and using different ripening temperatures

No standard technologically based manufacturing method exists for dry, fermented, spicy Turkish style sausage (soudjouk) and current techniques yield techniques yield unacceptable, mostly rancid and putrid products with high levels of residual NO⁻₃ and NO⁻₂. A standard method of soudjouk processing was developed. Three different starter cultures ( Lactobacillus plantarum, L. plantarum+Micrococcus aurantiacus, L. plantarum+M. aurantiacus+Debaryomyces hansenii ) were added to the soudjouk mixture and ripened at three different temperatures (12–14, 16–18 and 20–22°C). The addition of mixed cultures significantly reduced the residual NO⁻₃ and NO⁻₂ levels, increased the lipid soluble carbonyl levels, and produced low thiobarbituric acid values in the ripened soudjouks. For better quality characteristics, addition of D . hansenii is advisable and a ripening temperature of 20-22°C should be used.     

Effects of Short-term Exposure to Low O2 and High CO2 Atmospheres on Quality Attributes of Strawberries

Strawberries (Fragaria ananassa Duch., cv. ‘Selva') were stored 10 days in 1.0%, 0.5%, or 0.25% 0₂ or air + 20% CO₂; or 6 days in air + 50% or 80% CO₂ at 0 or 5°C without detrimental effects on quality. Decay and softening were reduced by treatments. An untrained taste panel, under ordinary eating conditions, did not consistently differentiate ‘Pajaro’ strawberries kept in 0.25% 0₂ from those stored in air. A trained taste panel, under controlled conditions, perceived slight off-flavor in ‘G3’ strawberries kept in 0.25% or 0% 0₂. This correlated with ethanol, ethyl acetate, and acetaldehyde in juice. The 50% or 80% CO₂ treatments caused injury after 8 to 10 days, while 20% CO₂ treatments did not. All high CO₂ treatments caused increase in pH of juice.     

Enterotoxin C2 Production by S. aureus in Entree Salads

Staphylococcus aureus strain 361 was inoculated into salads containing chicken, macaroni, potato, or artificially flavored soy product. Egg was added to some. The pH averaged 6.2 in the control made with water dressing rather than vinegar, 4.7 with home-style cooked salad dressing, and 4.9 with commercial salad dressing. Following incubation at 37°C for 8 or 24 hr, pH, total counts, and enterotoxin C₂ were determined. Enterotoxin was detected at 8 hr in all macaroni and potato dressing types. At 8 hr, enterotoxin was not detected in most soy product or chicken salads. By 24 hr the lowest levels were in the soy product salads but all products contained toxin. When the inoculum level was reduced below the 10⁵ CFU per g used in the main study, enterotoxin production was delayed but occurred at 8 hr if the inoculum level was 10³.     

Changes in the free -NH2, free -CO2H and titratable acidity of meat proteins

The 2, 4, 6-trinitrobenzene sulphonic acid (TNBS) spectrophotometric assay and formol titration were used to measure changes in free -NH₂ and free -CO₂H respectively, in meat proteins dissolved in 3% sodium dodecyl sulphate (SDS). Changes in the titratable acidity of the meats was also determined. The free -NH₂ groups were found to decrease markedly with cooking while -CO₂H remained relatively constant. Intermediate moisture beef ( Longissimus dorsi ) processed and stored at 38°C showed the free groups increasing for up to 8 weeks' storage due to proteolysis, followed later by a sharp fall due to cross-linking. But titratable acidity of the IM beef samples continued to rise with storage.     

Supercritical CO2 extraction of grappa volatile compounds

A first study on the recovery of aromatic extracts from grappa by means of supercritical fluid extraction (SFE) on a laboratory plant has been performed, to obtain aroma extracts at low ethanol content. The influence of extraction parameters like pressure, temperature and flow rate have been studied. Extraction yields have been evaluated for ethanol, higher alcohols and esters of short and medium chain acids. A higher aroma volatile compounds extraction has been obtained when the strongest extraction condition has been considered (200 bar, 60 °C, 0.3 kg h⁻¹). Sensory evaluation has indicated as preferred the extract obtained under mild condition (80 bar, 40 °C, 0.3 kg h⁻¹).