Oxygenation methods

Surface aeration is the simplest form and is sufficient for most laboratory applications. However, this is limited to laboratory-size reactors and becomes 

Stirred liquid surface 10-6-4 X 10-3 Sinskey et al (1981) Lavery Neinow (1987) Katinger Scheirer (1985) Aunins et al (1989) Johnson et al (1990) 

Sparged with agitation 7 X 10-3-2.5 Spier Griffiths (1984) Matsuoka et al (1992) 

Modified from Table 2 of Bliem Katinger (1988) by permission of Trends in Biotechnology. 

Oxygen can be supplied to the culture by directly sparging the supply gas into the bioreactor. The basic concepts describing mass transfer in gas-sparged bioreactors are reviewed in Moo-Young and Blanch (1981). Sparger aeration offers 

---

The effectiveness of antioxidants as preservatives for fats and oils is evaluated by determining the rate of peroxide development using the Active Oxygen Method (AOM) (29). The development of a rancid odor is used to evaluate the stabiUty of food items (Schaal Oven StabiUty test) (30). 

Active Oxygen Method," Technical Data Bulletin ZG-159c, Eastman Chemical Products, Inc., Kingsport, Term., Mar. 1985. 

This research used mechanically agitated tank reactor system shown in Fig. 1. The reactor, 102 mm in diameter and 165 mm in height, was made of transparant pyrex glass and was equipped with four baffles, 120 mm in length and 8 mm in width, and six blades disc turbine impeller 45 mm in diameter and 12 mm in width. The impeller was rotated by electric motor with digital impeller rotation speed indicator. Waterbath thermostatic, equipped with temperature controller was used to stabilize reactor temperature. Gas-liquid mass transfer coefficient kia was determined using dynamic oxygenation method as has been used by Suprapto et al. [11]. 

The possibility of isolating the components of the two above-reported coupled reactions offered a new analytical way to determine NADH, FMN, aldehydes, or oxygen. Methods based on NAD(P)H determination have been available for some time and NAD(H)-, NADP(H)-, NAD(P)-dependent enzymes and their substrates were measured by using bioluminescent assays. The high redox potential of the couple NAD+/NADH tended to limit the applications of dehydrogenases in coupled assay, as equilibrium does not favor NADH formation. Moreover, the various reagents are not all perfectly stable in all conditions. Examples of the enzymes and substrates determined by using the bacterial luciferase and the NAD(P)H FMN oxidoreductase, also coupled to other enzymes, are listed in Table 5. 

Since 1995, to improve rehabilitation in our Centre, the hyperbaric oxygenation method has been used in the postoperative period in patients with liver cirrhosis. HBO was carried out in a single barocamera BLKS-3-01 in pure oxygen (purity 99.5%) at pressure of 1.6-2.0 kg-force cm . The duration of a session was 40-60 min, and 8-10 sessions were required for one course of treatment. All patients had a determined individual indication for HBO. 

The ISO and the ASTM oxygen method and the ASTM air pressure method call for the pressure to be released slowly at the end of the exposure but ISO does not point out that this is to avoid porosity. Presumably, in the worst case it could be a test for explosive decompression. 

Rancidity measurements are taken by determining the concentration of either the intermediate compounds, or the more stable end products. Peroxide values (PV), thiobarbituric acid (TBA) test, fatty acid analysis, GC volatile analysis, active oxygen method (AOM), and sensory analysis are just some of the methods currently used for this purpose. Peroxide values and TBA tests are two very common rancidity tests however, the actual point of rancidity is discretionary. Determinations based on intermediate compounds (PV) are limited because the same value can represent two different points on the rancidity curve, thus making interpretations difficult. For example, a low PV can represent a sample just starting to become rancid, as well as a sample that has developed an extreme rancid characteristic. The TBA test has similar limitations, in that TBA values are typically quadratic with increasing oxidation. Due to the stability of some of the end-products, headspace GC is a fast and reliable method for oxidation measurement. Headspace techniques include static, dynamic and solid-phase microextraction (SPME) methods. Hexanal, which is the end-product formed from the oxidation of Q-6 unsaturated fatty acids (linoleate), is often found to be a major compound in the volatile profile of food products, and is often chosen as an indicator of oxidation in meals, especially during the early oxidative changes (Shahidi, 1994). 

The OSI replaced the Active Oxygen method (AOM), which is no longer recommended by the American Oil Chemists Society. The AOM required frequent measurement of peroxide value. Not only was this laborious, but determining peroxide value resulted in a... 

Active Oxygen Method (AOM), 535, 544 Adsorption, and interfacial properties diffusion and kinetic controlled models, 617-618 (figs.), 620-622 Gibbs adsorption isotherm, 617-619 kinetics of surface-active substances, 639... 

Laubli, M.W and Bruttel, P.A.(1986) Determination of the oxidative stability of fats and oils comparison between the active oxygen method and the rancimat metho lm. Oil Chem. So,c.63 792-795. 

Zhang S, Handa-Corrigan A, Spier RE (1993), A comparison of oxygenation methods for high-density perfusion cultures of animal cells, Biotechnol. Bioeng. 41 685-692. 

A 1-10 mg specimen (typically between 2 and 5 mg) is heated at a constant rate between 0.2 and 2 K/s in the lower chamber. Decomposition can take place in nitrogen (method A) or in a mixture of nitrogen and oxygen (method B). When method A is used, charforming specimens do not decompose completely and leave a solid residue. In this case, the volatiles are mixed with a metered supply... 

In a study by Chipault et al. (1952) to test the stabilizing effect of 36 different spices on lard by the active oxygen method... 

Active Oxygen Method for Fat Stability (AOM) (Cd 12-57) determines the time (in hours) for a sample of fat or oil to attain a predetermined peroxide value (PV) under the conditions of the test. The method is used to estimate the comparative oxidative stability of fats and oils. The method has been placed in surplus, in favor of Cd 12b-92 (Oil Stability Index), but retains official status and is still used in domestic industry. p-Anisidine Value (AV) (Cd 18-90) determines the amount of aldehydes (principally 2-alkenals and 2,4-dienals) in animal and vegetable fats and oils. These are degradation products of peroxides, which are not removed by bleaching. Some fats and oils chemists propose increased use of this method in purchase specifications. Bleaching Test for Soybean Oil (Cc 8e-s63) determines the color of a sample of soybean oil after treatment with a specified bleaching earth. Specific methods exist for other oil species. 

Stability (Active Oxygen Method) Not less than 50 h. Unsaponifiable Matter Not more than 1.5%. 

STABILITY (Active Oxygen Method) (Based on AOCS Method Cd 12-57)... 

Table 2-25 Active Oxygen Method (AOM) Time of Several Oils and Fats as Determined by Peroxide Value and Conductivity Measurements...

Shelf stability test Shelf life is predicted by the active oxygen method (AOM). The fat or oil is subjected to an accelerated oxidation test under standardized conditions so that the signs of deterioration are revealed within several hours or days. The sample is heated at 97.8°C while air is blown through it. The AOM value is reported as the number of hours to reach a peroxide value of 100 meq/kg. 

The headspace oxygen method is simple and reproducible and may be the best analytical method to evaluate the oxidative stability of fats and oils (14). Its application in measurement of lipid oxidation in food products other than fats and oils, however, is limited because protein oxidation also absorbs oxygen (15). 

---