Alpha-tocopherol oxidation in fish muscle during chilling and frozen storage

The oxidation of alpha-tocopherol (TH) in chilled and frozen fish muscle was determined using high-performance liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry. TH oxidation byproducts were identified as alpha-tocopherolquinone (TQ), 5,6-epoxy-alpha-tocopherolquinone (TQE1), and 2-3-epoxy-alpha-tocopherolquinone (TQE2). The concentration of TH decreased significantly during storage while those of TQ, TQE1, and TQE2 increased noteworthy. The relative amounts of TH and its oxidized products were significantly related with the extent of oxidation produced in postmortem fish, and the ratio TQ/TH is suggested as an index of oxidative stress in fish muscle. The effect of phenolic antioxidants supplementation on retarding TH oxidation was also studied. Data suggested that the addition of 100 ppm of caffeic acid, hydroxytyrosol, and propyl gallate could regenerate endogenous TH from its oxidized forms resulting in an antioxidant synergy consistent with the reduction of lipid oxidation observed in fish muscle supplemented with phenolic compounds.     

Fluorescence, browning index, and color in infant formulas during storage

Free and total fluorescent compounds, browning index, and color formation were measured in milk-based powdered infant formulas (IF) during 2 years of storage at 20 and 37 degrees C. The excitation spectra from 415 nm emission show three peaks (ex lambda1 = 270 nm, lambda2 = 325/315 nm, lambda3 = 350 nm) and from 347 nm excitation two emission peaks (415 and 520 nm), and no wavelength shifts were observed. Temperature and time of storage exert in general no significant effect on the development of fluorescence emission intensity and browning index. However, an important increase in pentodilysine was recorded-probably because of the iron and ascorbic acid contents of the samples-as well as in browning index in adapted IF. In both IF a color increase (deltaE) throughout storage was observed, this increase being greater in samples stored at 37 degrees C than in those stored at 20 degrees C. The increase in color with time fitted a linear regression model. Color appeared to be an indicator of sufficient sensitivity to measure the effect of temperature or storage time.     

Changes in the lipid composition of powdered infant formulas during long-term storage

Changes in the lipid composition of two standard infant formulas induced by 4 years of storage were determined. Lipids were thoroughly analyzed using different gas-liquid and liquid-liquid chromatographic techniques. Oleic acid and linoleic acid, which accounted for almost the total monounsaturated and polyunsaturated fatty acids, respectively, showed slight but significant decreases (P < 0.05) during the 4 years of storage (from 41.52 to 39.83% for oleic acid and from 17.35 to 15.99% for linoleic acid). Total trans fatty acid isomers showed low initial level (0.22% of total fatty acids), and such level remained unchanged during the storage period. Nonvolatile oxidation compounds including oxidized, dimeric, and polymeric triglycerides did not significantly increase during the storage period, although a significant loss of tocopherols was found in the surface oil fraction (10-15%). In general, the results obtained indicate that, although small losses of oleic and linolenic acid as well as tocopherols were found, the 4 year storage period did not lead to relevant changes in the lipid fraction of infant formulas.     

Progress of browning reactions during storage of liquid infant milks.

Changes in furfural compounds and reactive lysine were monitorized in three commercial liquid infant milks during 9 months of storage at 20, 30, and 37 degrees C. Samples consisted of two ultrahigh temperature (UHT)-treated milks and one conventionally sterilized milk. Reactive lysine remained constant throughout storage at the three temperatures, whereas, in general an increase in furfural compounds was observed. The heat treatment used in the manufacture of milk is an important factor that influences the levels of furfural compounds although the composition of the milk is also a critical factor. Finally, a study was conducted to find the kinetic equations describing furfural compounds changes and allowing for the prediction of the influence of time and temperature of storage on those changes.     

Optimization of tannin extraction from infant foods

The design of experiments (DOE) was used in the development of a laboratory procedure for the extraction of tannins from three infant food types comprising different ingredients of vegetable origin and meat. The diversity of vegetables included in the product formulas required the use of DOE to establish parameters that maximize the recovery of tannins using a central composite rotatable design. Once the experimental results from the DOE were obtained, response surface methodology was used to find the best analytical conditions for samples comprising different ingredients. Sample weight was found to be a critical factor in tannin extraction from foods. Different optimal conditions were obtained for samples including soya in the formula.     

Lipid oxidation in fillets of herring (Clupea harengus) during ice storage

The influence of ice storage on lipid oxidation, odor, antioxidants, water-soluble catalysts, and microorganisms was investigated in fillets of herring (Clupea harengus) during 15 days. Based on linear regression analyses of the data, significant rises (p ascorbic acid > glutathione peroxidase (GSH-px); however, GSH-px correlated best to the development of lipid oxidation products (r(mean) = -0.96). The activity of aqueous pro-oxidants, which were enzymatic in nature to a great extent, had decreased by 75% at day 15. No significant increase in total bacteria was seen until after 7 days. There were major local differences in both composition and stability throughout the fillet. Oxidation proceeded most rapidly in the tissue right under the skin, probably explained by its high initial pro-oxidative activity.     

Survey of infant foods for Clostridium botulinum spores

A total of 236 samples of infant foods, including honey, dry cereal, nonfat dry milk, evaporated milk, canned formula, and canned baby food, were collected in the New York City area and tested for the presence of Clostridium botulinum spores. Methods for recovery of spores were validated using foods spiked with 4 spores/mL or g. None of the products contained C. botulinum spores, indicating that their incidence in these commercial foods is not widespread. This limited study did not identify any food types that could be suspected of being involved in the transmission of infant botulism.     

Lipid oxidation in fillets of herring (Clupea harengus) during frozen storage. Influence of prefreezing storage.

Fillets of herring (Clupea harengus) were kept on ice for 0, 3, 6, and 9 days prior to storage at -18 degrees C for 0, 21, 42, 63, and 84 days. At each storage point, peroxide value (PV), absorbance at 268 nm (A(268)), fluorescent products (FP), alpha-tocopherol, glutathione peroxidase (GSH-px) activity, and ascorbic acid were measured. As shown by regression analyses, samples held for 6 days on ice formed oxidation products at the highest rate during frozen storage, followed by, for PV and FP, the 9-day samples. These data indicate that severe changes that negatively affect the oxidation process took place in the herring muscle between 3 and 6 days after catch. Both the initial antioxidant levels and the rate of antioxidant loss at -18 degrees C decreased with increased prefreezing holding time, the latter being most obvious for GSH-px activity and ascorbic acid. alpha-Tocopherol showed the largest losses and had disappeared entirely from the 6- and 9-day samples at the end of the frozen storage. Partial least-squares regression analysis of the data showed that ice storage had a greater effect than frozen storage on changes in PV, A(268), FP, alpha-tocopherol, and ascorbic acid. For GSH-px activity, frozen storage had the greatest effect.     

Method for maintaining viability of Clostridium perfringens in foods during shipment and storage: collaborative study.

A collaborative study was conducted in 12 laboratories to determine the effectiveness of a new method for maintaining vegetative cells of Clostridium perfringens in viable condition during storage and transport of food specimens to the laboratory. The collaborative results showed that treatment of brown gravy and roast beef samples with an equal amount by weight of sterile buffered glycerol-sodium chloride solution to give a final 10% glycerol concentration and storage with Dry Ice for 10 days at -56 degrees C resulted in plate counts of C. perfringens which were 2-4 log cycles higher with 2 different strains than counts with untreated specimens stored by the usual method at -20 degrees C. Plate counts obtained with the treated specimens stored with Dry Ice were less than 1 log cycle lower than counts made with identical specimens before freezing for storage and shipment to the collaborators. The results with treated specimens were also more uniform among the different laboratories. Because the new method for storage and shipment of food samples was so effective for maintaining viability of the organism, the official first action method for C. perfringens (46.B01) was changed to incorporate these procedures as part of the method.     

Lactoferrin in infant formulas: effect on oxidation

Lactoferrin is an iron transport protein present in human milk at an average concentration of 1.4 mg/mL. Commercially modified infant formulas based on cow's milk contain much lower amounts of lactoferrin (0.1 mg/mL lactoferrin) and soy based formulas have none. In addition to its role in iron transport, lactoferrin has bacteriostatic and bactericidal activities. Infant formulas are supplemented with relatively large amounts of iron (up to 12 mg/L). The effect of various concentrations of added lactoferrin and supplemental iron on lipid oxidation was tested in two different infant formulas. The extent of oxidation in the formulas as a function of time was determined by formation of hydroperoxides, production of hexanal, and fluorescence. On the basis of all three of these determinations, lactoferrin acted as an antioxidant in the absence and presence of different concentrations of supplemented iron. Lactoferrin inhibited oxidation in a concentration-dependent manner even at concentrations beyond its capacity to bind iron at its two high affinity binding sites. Lactoferrin can be used, therefore, as a dual purpose additive in infant formulas and similar food products for its antioxidant and its antimicrobial properties.     

Protein and lipid oxidation during frozen storage of rainbow trout (Oncorhynchus mykiss)

This study aimed at investigating protein and lipid oxidation during frozen storage of rainbow trout. Rainbow trout fillets were stored for 13 months at -20, -30, or -80 degrees C, and samples were analyzed at regular intervals for lipid and protein oxidation markers. Lipid oxidation was followed by measuring lipid hydroperoxides (PV), as well as secondary oxidation products (volatiles) using dynamic headspace GC-MS. Free fatty acids (FFA) were measured as an estimation of lipolysis. Protein oxidation was followed using the spectrophotometric determination of protein carbonyls and immunoblotting. Significant oxidation was observed in samples stored at -20 degrees C, and at this temperature lipid and protein oxidation seemed to develop simultaneously. FFA, PV, and carbonyls increased significantly for the fish stored at -20 degrees C, whereas the fish stored at -30 and -80 degrees C did not show any increase in oxidation during the entire storage period when these methods were used. In contrast, the more sensitive GC-MS method used for measurement of the volatiles showed that the fish stored at -30 degrees C oxidized more quickly than those stored at -80 degrees C. Detection of protein oxidation using immunoblotting revealed that high molecular weight proteins were oxidized already at t = 0 and that no new protein oxidized during storage irrespective of the storage time and temperature. The results emphasize the need for the development of more sensitive and reliable methods to study protein oxidation in order to gain more explicit knowledge about the significance of protein oxidation for food quality and, especially, to correlate protein oxidation with physical and functional properties of foods.     

Peroxynitrite-induced oxidation of lipids: implications for muscle foods.

Peroxynitrite (ONOO(-)), formed from the nearly diffusion limited reaction between nitric oxide and superoxide, could be an important prooxidant in muscle foods. The objective of this study was to determine whether peroxynitrite caused oxidation of pyrogallol red, liposomes, muscle microsomes, and skeletal muscle homogenate. Oxidation of pyrogallol red, liposomes, and microsomes initiated by peroxynitrite continuously produced by 3-morpholinosydnonimine (SIN-1, 2 mM) was time-dependent and enhanced by CO(2) (1 mM). Reagent peroxynitrite (2 mM) caused concentration-dependent oxidation of pyrogallol red, liposomes, and muscle microsomes that was very rapid with no change after 5 min. Peroxynitrite-induced oxidation was suppressed by CO(2) and low pH. Skeletal muscle homogenate oxidized by reagent peroxynitrite (0.5 mM) exhibited gradual oxidation with time and was suppressed by CO(2), low pH, and metal chelators. These data suggest that peroxynitrite could be an important prooxidant in muscle foods.     

Effects of ultra-high-pressure homogenization treatment on the lipolysis and lipid oxidation of milk during refrigerated storage

Free fatty acid (FFA) release and quantification and lipid oxidation extent of ultra-high-pressure homogenized (UHPH) milk samples were evaluated to assess the effect of UHPH on the susceptibility of milk lipids to lipolysis and oxidation. Milk was UHPH-treated at 200 and 300 MPa with inlet temperatures of 30 and 40 degrees C. UHPH-treated samples were compared to high-pasteurized milk (PA; 90 degrees C, 15 s). Results showed that all FFA increased significantly during storage only in 200 MPa samples. Lipid oxidation was measured as an accumulation of lipid hydroperoxides as the primary oxidation product and malondialdehyde and hexanal as the secondary oxidation products. Samples treated at 300 MPa presented higher malondialdehyde and hexanal content compared to 200 MPa treated-samples and to PA milk.     

Ionizing radiation and antioxidants affect volatile sulfur compounds, lipid oxidation, and color of ready-to-eat Turkey bologna

Bologna was processed from ground turkey breast meats containing one of four antioxidant treatments (none, rosemary extract, sodium erythorbate, and sodium nitrite). After it was cooked, the bologna was sliced, sealed in gas impermeable bags, exposed to 0, 1.5, and 3.0 kGy gamma-radiation, and then stored at 5 degrees C for up to 8 weeks. Thiobarbuturic acid reactive substances (TBARS), color, and volatile sulfur compounds were measured every 2 weeks during storage. Irradiation had no consistent effect on TBARS values. The rosemary extract and sodium nitrite inhibited, while erythorbate increased, TBARS values, independent of radiation dose or storage time. Irradiation promoted redness and reduced yellowness of the control (no antioxidant) bologna at weeks 0 and 2. The use of nitrite and rosemary extract inhibited the changes in color due to irradiation. Several volatile sulfur compounds (hydrogen sulfide, methanethiol, methyl sulfide, and dimethyl disulfide), measured using a pulsed flame photometric detector, increased with radiation dose. However, none of the antioxidants had any substantial effect on volatile sulfur compounds induced by irradiation. Our results suggest that antioxidants did not consistently affect irradiation-induced volatile sulfur compounds of turkey bologna although they did significantly impact color and lipid oxidation.     

Determination of pesticides in apple-based infant foods using liquid chromatography electrospray ionization tandem mass spectrometry

A liquid chromatography electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method was developed and validated to quantify and confirm trace levels of 13 pesticides including aldicarb sulfoxide, aldicarb sulfone, oxamyl, methomyl, formetanate, 3-hydroxycarbofuran, carbendazim, thiabendazole, aldicarb, propoxur, carbofuran, carbaryl, and methiocarb in apple-based infant foods such as apple sauces, apples and strawberries, apples and blueberries, and apples and plums. Data acquisition under MS/MS was achieved by applying multiple reaction monitoring of two fragment ion transitions to provide a high degree of sensitivity and selectivity for both quantification and confirmation. LC/ESI-MS/MS quantitative results were significantly affected by matrices, and thus, the standard addition was employed to compensate for the matrix effects to achieve the best accuracy of the method. Recoveries of 13 pesticides, spiked at 5.0, 25.0, and 45.0 microg/kg, were around 100% using the LC/ESI-MS/MS standard addition. The method detection limits (S/N > or = 3:1) of 13 pesticides were less than 0.2 microg/kg.     

Lipid oxidation in herring fillets (Clupea harengus) during ice storage measured by a commercial hybrid gas-sensor array system

Volatile compounds released from herring fillets (Clupea harengus) during 15 days of storage on ice have been measured with a commercial hybrid gas-sensor array system. Using partial least-squares regression modeling, the sensor responses were correlated with data from chemical analyses (lipid oxidation products and antioxidants) and sensory analyses (odor). Eight of the 16 sensors proved significant in the correlation studies: 6 metal oxide semiconductor field effect transistor (MOSFET) sensors and 2 Taguchi type sensors. Correlation coefficients for chemical and sensory data ranged from 0.9 to 0.98 and from 0.49 to 0.92, respectively, with 0.92 referring to both "sharp/acrid" and "rancid" odors. Prediction errors ranged from 8 to 14% and from 11 to 25% for the chemical and sensory measures, respectively. That the prediction errors for oxidation product formation (5-9%) were close to the analytical errors of the chemical reference methods indicated close to "optimum" performance of the gas-sensor system. The sensor system predicted the storage time of the herring with a 1-day error. Results illustrate high potential of the gas-sensor technology in rapid nondestructive quality determination of ice-stored herring.     

Improved storage stability of model infant formula by whey peptides fractions

The purpose of this study was to evaluate the shelf-life stability (6 months) of model infant formula with whey protein hydrolysates or peptidic fractions as carrageenan replacers. Whey protein hydrolysates were prepared with trypsin and followed by ultrafiltration of the hydrolyzed mixture, and peptidic fractions were isolated from the ultrafiltered tryptic hydrolysate by anion- or cation-exchange chromatography. The stability of the model infant formula was evaluated using a stratification method based on fat content differences between the top and bottom strata of the samples. With protein hydrolysate-based formulations, the creaming rate of the fat in the product was slightly higher than in the standard formulation (with carrageenan), which is indicative of lower storage stability. The addition of cationic fractions to model infant formula also resulted in lower product stability, whereas the fat creaming rate was retarded in anionic fraction based formulations. The physicochemical characteristics of certain peptides combined with the reported high emulsifying properties of peptidic sequences found within these fractions may account for their ability to act as carrageenan replacers.     

Role of the raw composition of pelagic fish muscle on the development of lipid oxidation and rancidity during storage

The muscle composition of a pelagic fish species, Atlantic mackerel (Scomber scombrus), has been studied to determine the relationship with its susceptibility to develop lipid oxidation during chilled storage. For such an aim, the initial concentrations of the major components (water, total lipids, protein, and PUFAs) and minor pro-oxidant and antioxidant components (ascorbic acid, α-tocopherol, hemoglobin, total iron, LMW-iron, copper, and zinc) of different batches of mackerel were characterized. For the study, several batches of mackerel were caught during the spring and summer periods. The different batches were subjected to chilled storage, and the onset of lipid oxidation was statistically related with the initial muscle composition. Results showed significant compositional differences among the mackerel lots, especially for the muscle lipid content (2.83-9.50%). In a first step, a Pearson correlation test was used to check the influence of each component on the progress of lipid oxidation. Results showed a significant relationship between shelf life and water and total lipid contents. Multiple regression was performed to reveal the contribution of each component to the susceptibility to lipid oxidation. The model obtained combines the content of PUFAs, total iron, hemoglobin, and ascorbic acid. An accurate prediction of shelf life in terms of rancidity was achieved by the model created (R(2) = 0.9975). These results establish that the levels of endogenous pro-oxidants and antioxidants present in fish muscle together with the polyunsaturated lipids are relevant factors affecting the shelf life of mackerel muscle.     

Changes in organosulfur compounds in garlic cloves during storage

We determined the changes in the contents of three gamma-glutamyl peptides and four sulfoxides in garlic cloves during storage at -3, 4, and 23 degrees C for 150 days using a validated high-performance liquid chromatography method that we reported recently. When garlic was stored at 4 degrees C for 150 days, marked conversion of the gamma-glutamyl peptides, gamma-L-glutamyl-S-allyl-L-cysteine and gamma-L-glutamyl-S-(trans-1-propenyl)-L-cysteine (GSPC), to sulfoxides, alliin and isoalliin, was observed. Interestingly, however, when garlic was stored at 23 degrees C, a decrease in GSPC and a marked increase in cycloalliin, rather than isoalliin, occurred. To elucidate in detail the mechanism involved, the conversion of isoalliin to cycloalliin in both buffer solutions (pH 4.6, 5.5, and 6.5) and garlic cloves at 25 and 35 degrees C was examined. Decreases in the concentration of isoalliin in both the solutions and the garlic cloves during storage followed first-order kinetics and coincided with the conversion of cycloalliin. Our data indicated that isoalliin produced enzymatically from GSPC is chemically converted to cycloalliin and that the cycloalliin content of garlic cloves increases during storage at higher temperature. These data may be useful for controlling the quality and biological activities of garlic and its preparations.