Oxidative stability and non‐enzymatic browning reactions in Antarctic krill oil (Euphausia superba)

Antarctic krill oil has gained much consideration recently due to its rich content of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the form of phospholipids and its powerful antioxidant known as astaxanthin. To secure these valuable bioactive nutrients in krill oil, a gentle and immediate on‐board processing of freshly captured krill is recommended. Compared to fish oil, krill oil has a more complex matrix, which leads to the formation of additional compounds from non‐enzymatic browning reactions. Lipid oxidation occurs through different pathways in krill oil and cannot be detected through classical analytical techniques such as determination of peroxide and anisidine value. Therefore selection of appropriate methods to evaluate the oxidative stability of krill oil is of high importance.

Figure 1 Open in figure viewer PowerPoint Development of lipid derived volatiles: (a & b) 1‐penten‐3‐ol and (c & d) 2‐pentylfuran in krill oil upon storage at two different incubation temperatures (20 and 40°C). The same pattern as (a & b) was obtained for (Z)‐2‐penten‐1‐ol and benzaldehyde, whereas the same pattern as (c & d) was obtained for 2‐heptanone and 2‐octanone. Values are mean ± SD (n = 3). Means sharing the same letter are not significantly different at 5% significant level. Reproduced from Lu et al. 2 with permission from Elsevier.     

Comparison of two methods for extraction of volatiles from marine PL emulsions

The dynamic headspace (DHS) thermal desorption principle using Tenax GR tube, as well as the solid phase micro‐extraction (SPME) tool with carboxen/polydimethylsiloxane 50/30 µm CAR/PDMS SPME fiber, both coupled to GC/MS were implemented for the isolation and identification of both lipid and Strecker derived volatiles in marine phospholipids (PL) emulsions. Comparison of volatile extraction efficiency was made between the methods. For marine PL emulsions with a highly complex composition of volatiles headspace, a fiber saturation problem was encountered when using CAR/PDMS‐SPME for volatiles analysis. However, the CAR/PDMS‐SPME technique was efficient for lipid oxidation analysis in emulsions of less complex headspace. The SPME method extracted volatiles of lower molecular weights more efficient than the DHS method. On the other hand, DHS Tenax GR appeared to be more efficient in extracting volatiles of higher molecular weights and it provided a broader volatile spectrum for marine PL emulsion than the CAR/PDMS‐SPME method.     

Effect of classic sterilization on lipid oxidation in model liquid milk‐based infant and follow‐on formulas

The objective of this study was to evaluate the effect of classic sterilization on lipid oxidation of liquid infant and follow‐on formulas by analyzing formation of oxidized and dimeric TAGs. Model systems containing similar components and proportions to those normally found in manufactured samples and a mixture of high‐oleic sunflower oil, rapeseed oil, and fish oil were used to obtain a fatty acid composition profile in accordance with the EU regulations. For comparative purposes, some samples were prepared with high‐oleic sunflower or fish oil and others without the protein components and added Tween‐20. Quantification of total oxidized TAGs provided complete information of the oxidation state and showed clear advantages versus the other methods used, i.e., loss of PUFA and peroxide value. The results showed that the heat treatment used for sterilization did not lead to significant lipid oxidation, but the tocopherol concentration decreased significantly. The marked tocoherol losses found in protein‐free formulas together with the significantly lower tocopherol concentrations in infant formulas (80% whey in protein fraction) compared to follow‐on formulas (80% caseinate in protein ratio) showed the protective effect of the protein fraction, specially sodium caseinate. Practical applications: This study provides useful information on the utility of different methods used to evaluate oxidation in infant and follow‐on formulas. Quantification of total oxidized TAGs standed out because it is a direct and sensitive method and provides complete information at any stage of the oxidative process. Also, this study shows that important decreases of tocopherols may occur during formula processing and special cautions should therefore be taken during storage and commercialization to avoid additional antioxidant losses.     

Effects of ferric chloride on thermal degradation of γ‐oryzanol and oxidation of rice bran oil

The kinetics of γ‐oryzanol degradation in antioxidant‐stripped rice bran oil were investigated at 180°C for 50 h. Ferric chloride was added to the oil at different concentrations (0, 2.5, 5.0, and 7.5 mg/kg‐oil) to determine the degradation reaction rate of γ‐oryzanol and the extent of lipid oxidation (peroxide value and p‐anisidine value). It was found that the losses of γ‐oryzanol and its four components (cycloartenyl ferulate, 24‐methylene cycloartanyl ferulate, campesteryl ferulate, and β‐sitosteryl ferulate) could be described by a first‐order kinetics model. The degradation rate constant, k, linearly increased (p < 0.05) with the ferric chloride concentration, and increased about 1.5 times when 7.5 mg/kg‐oil ferric chloride was added. Ferric chloride addition also accelerated the lipid oxidation of rice bran oil significantly (p < 0.05). Practical applications: This paper describes the kinetic analysis of the degradation of γ‐oryzanol, a major phytochemical in rice bran oil, at its frying temperature. The results indicated that iron in the form of ferric chloride accelerated both the degradation of γ‐oryzanol and lipid oxidation.     

A comparison of commercial enzymes for the aqueous enzymatic extraction of corn oil from corn germ

An aqueous enzymatic method was developed to extract corn oil from corn germ. The basic steps in the method involved “churning” the corn germ with various enzymes and buffer for 4 h at 50°C, and an additional 16 h at 65°C, followed by centrifugation and removal of the oil layer from the surface. No hexane or other organic solvents are used in this process. By using oven-dried corn germ samples (6 g) from a commercial corn wet mill, corn oil yields of about 80% were achieved using three different commercial cellulases. A fourfold scale-up of the method (to 24 g of germ) resulted in oil yields of about 90%. Nine other commercial enzymes were evaluated and resulted in significant but lower oil yields. In the absence of enzymes, oil yields of 27 to 37% were achieved. The chemical compositions of hexane-extracted vs. aqueous enzymatic-extracted corn oils were very similar.     

Effect of high‐pressure treatment on microbial activity and lipid oxidation in chilled coho salmon

This work studies the effect of a previous hydrostatic high‐pressure (HHP) treatment on chilled farmed coho salmon (Oncorhynchus kisutch). Three different HHP conditions were applied (135 MPa‐30 s, 170 MPa‐30 s, and 200 MPa‐30 s for treatments T‐1, T‐2, and T‐3, respectively) and compared to untreated (control) fish throughout a 20‐day chilled storage. Microbial activity and lipid oxidation development were analyzed. Assessment of aerobe, psychrotroph, Shewanella spp. and Pseudomonas spp. counts and trimethylamine formation showed a marked inhibitory effect (p <0.05) of HHP treatment on microbial activity, with this effect increasing with the pressure value employed. Related to lipid oxidation development, higher peroxide mean values (day 10–20 period) were found in control samples and fish treated under T‐1 condition when compared to their counterparts corresponding to T‐2 and T‐3 treatments. On the contrary, quantification of thiobarbituric acid‐reactive substances and fluorescent interaction compounds showed higher levels (p <0.05) in fish samples corresponding to T‐2 and T‐3 treatments. In spite of the lipid oxidation development found, polyene index and tocopherol isomer (α and γ) content did not provide differences (p >0.05) as a result of previous HHP treatment.     

An optimization and modeling approach for H2O2/UV‐C oxidation of a commercial non‐ionic textile surfactant using central composite design

BACKGROUND: Industrial surfactants are biologically complex organics that are difficult to degrade and may cause ecotoxicological risks in the environment. Until now, many scientific reports have been devoted to the effective treatment of surfactants employing advanced oxidation processes, but there is no available experimental study dealing with the optimization and statistical design of surfactant oxidation with the well‐established H₂O₂/UV‐C process. RESULTS: Considering the major factors influencing H₂O₂/UV‐C performance as well as their interactions, the reaction conditions required for the complete oxidation of a commercial non‐ionic textile surfactant, an alkyl ethoxylate, were modeled and optimized using central composite design‐response surface methodology (CCD‐RSM). Experimental results revealed that for an aqueous non‐ionic surfactant solution at an initial chemical oxygen demand (COD) of 450 mg L^?1, the most appropriate H₂O₂/UV‐C treatment conditions to achieve full mineralization at an initial pH of 10.5 were 47 mmol L^?1 H₂O₂ and a reaction time of 86 min (corresponding to a UV dose of 30 kWh m^?3). CONCLUSION: CCD allowed the development of empirical polynomial equations (quadratic models) that successfully predicted COD and TOC removal efficiencies under all experimental conditions employed in the present work. The process variable treatment time, followed by the initial COD content of the aqueous surfactant solution were found to be the main parameters affecting treatment performance, whereas the initial H₂O₂ concentration had the least influence on advanced oxidation efficiencies. The H₂O₂ concentration and surfactant COD were found to be more important for TOC abatement compared with COD abatement. Copyright © 2009 Society of Chemical Industry     

Photo‐oxidation of polymers: Validation of oxygen uptake and relationship with extent of hydroperoxidation

In this piece of work we focused our attention on the peroxidation step and alongside considered hydroperoxides as probes for the overall oxidative process. This technique of oxygen uptake actually monitors the amount of oxygen consumed during polymer degradation. Our present work aimed to investigate this technique to evaluate the oxygen uptake during in situ photoirradiation, under controlled atmosphere. Our experimental results clearly elucidate that the oxygen consumption data accounts for a very early stage of aging during the photo‐oxidation of polymers and provides us with an accurate and sensitive diagnosis about the formation of hydroperoxides. A straight‐line relationship was exhibited under our experimental conditions while observing a relation between oxygen pressure drop and hydroperoxide content in the polymer. This correlation was dependent upon the nature of polymer and of course on the aging conditions (temperature, irradiation, oxidative atmosphere). The impact of environmental atmosphere on aging was particularly kept in mind. To conclude, we emphasized that oxygen uptake is a promisingly powerful tool to identify the impact of the overall environmental parameters on the polymer photoaging. An important implication was on the understanding of atmospheric factors (including pollutants such as O₃, NO_x, etc.), which is usually given minor importance, on the degradation of polymer upon outdoor weathering. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Characterization of the mechanical properties,crystallization, and enzymatic degradation behavior of poly(butylene succinate‐co‐ethyleneoxide‐co‐DL‐lactide) copolyesters

A series of aliphatic biodegradable poly (butylene succinate‐co‐ethyleneoxide‐co‐DL ‐lactide) copolyesters were synthesized by the polycondensation in the presence of dimethyl succinate, 1,4‐butanediol, poly(ethylene glycol), and DL ‐oligo(lactic acid) (OLA). The composition, as well as the sequential structure of the copolyesters, was carefully investigated by ¹H‐NMR. The crystallization behaviors, crystal structure, and spherulite morphology of the copolyesters were analyzed by differential scanning calorimetry, wide angle X‐ray diffraction, and polarizing optical microscopy, respectively. The results indicate that the sequence length of butylene succinate (BS) decreased as the OLA feed molar ratio increasing. The crystallization behavior of the copolyesters was influenced by the composition and sequence length of BS, which further tuned the mechanical properties of the copolyesters. The copolyesters formed the crystal structures and spherulites similar to those of PBS. The incorporation of more content of ethylene oxide (EO) units into the copolyesters led to the enhanced hydrophilicity. The more content of lactide units in the copolyesters facilitated the degradation in the presence of enzymes. The morphology of the copolyester films after degradation was also studied by the scanning electron microscopy. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Thermally induced crystallization and enzymatic degradation studies of poly (L‐lactic acid) films

Poly(L ‐lactic acid) (PLLA) films with different crystallinities were prepared by solvent casting and subsequently annealed at various temperatures (T_a) (80–110°C). The effects of crystallinity on enzymatic degradation of PLLA films were examined in the presence of proteinase K at 37°C by means of weight loss, DSC, FTIR spectroscopy, and optical microscopy. DSC and the absorbance ratio of 921 and 956 cm^?1 (A₉₂₁/A₉₅₆) were used to evaluate crystallinity changes during thermally induced crystallization and enzymatic hydrolysis. The highest percentage of weight loss was observed for the film with the lowest initial crystallinity and the lowest percentage of weight loss was observed for the film with highest crystallinity. FTIR investigation of degraded films showed a band at 922 cm^?1 and no band at 908 cm^?1 suggested that all degraded samples form α crystals. The rate of degradation was found to depend on the initial crystallinity of PLLA film and shown that enzymatic degradation kinetics followed first‐order kinetics for a given enzyme concentration. DSC crystallinity and IR absorbance ratio, A₉₂₁/A₉₅₆ ratio, showed no significant changes with degradation time for annealed PLLA films whereas as‐cast PLLA film showed an increase in crystallinity with degradation; this revealed that degradation takes place predominantly in the free amorphous region of annealed PLLA films without changing long range and short range order © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Shelf‐life prediction of perilla oil by considering the induction period of lipid oxidation

Kinetic models for the induction period (IP) of lipid oxidation were developed to predict the shelf‐life of perilla oil during storage. The degree of lipid oxidation was measured in terms of peroxide values (PV). The perilla oil was stored in the dark at various temperatures. The IP was measured at the intersection point of two linear lines and in terms of time and PV at the IP. The IP was expressed by an Arrhenius‐like relationship. Before and after the IP, the reaction followed pseudo‐zero‐order kinetics. The oxidation degrees according to storage times were computed by considering the variables, IP and reaction rate constants. The prediction model equation that was developed to determine shelf‐life is more accurate than in previous studies. Conclusively, considering the IP of lipid oxidation is essential for predicting the shelf‐life of perilla oil and is expected to be applicable to other vegetable oils. Practical applications : In kinetic modeling for shelf‐life estimation in terms of lipid oxidation, induction period (IP) is rarely considered. Thus the estimation of peroxide values (PV) from such models might be inaccurate. The IP was observed in perilla oil oxidation and kinetic models involving the IP were developed. This work enables a better estimation of oxidation. Besides, a shelf‐life diagram of perilla oil has been constructed as a valuable tool for quality control in the food industry.