Heat treatment, detection

Phosphatase Test. The phosphatase [9001-78-9] test is a chemical method for measuring the efficiency of pasteurization. AH raw milk contains phosphatase and the thermal resistance of this enzyme is greater than that of pathogens over the range of time and temperature of heat treatments recognized for proper pasteurization. Phosphatase tests are based on the principle that alkaline phosphatase is able, under proper conditions of temperature and pH, to Hberate phenol [108-95-2] from a disodium phenyl phosphate substrate. The amount of Hberated phenol, which is proportional to the amount of enzyme present, is determined by the reaction of Hberated phenol with 2,6-dichloroquinone chloroimide and colorimetric measurement of the indophenol blue formed. Under-pasteurization as well as contamination of a properly pasteurized product with raw milk can be detected by this test. 

Aside from isomerization, transformation of the 5,6-epoxy to the 5,8-furanoid group is a common alteration during heating treatments of carotenoids. Violaxanthin was found to be the major carotenoid in mangoes however, in commercially processed mango juice, violaxanthin was not detected while auroxanthin, not present in the... 

Enzyme activity can indicate the exposure of honey to heating and long storage. This criterion is not more accurate than the HMF content value because enzyme activities vary with honey samples. The diastase activity is usually associated with heat treatment. However, its activity gives only an indication about the processing (heat treatment) of the honey but is not suitable for the detection of the origin. 

It turns out that in solutions of c < 0.1 gL 1 thermosensitive homopolymers, such as PNIPAM, PVCL, and PVME, themselves, form stable colloids in water at elevated temperature in the absence of additives or chemical modification [141-147]. The colloids remain stable upon prolonged heat treatment, without detectable aggregation or precipitation. Also, core-shell particles consisting of PNIPAM and a hydrophobic block are stable not only below but also above the LCST up to 50 °C, when the PNIPAM block is expected to be insoluble [185]. Factors that determine the colloidal stability as defined in Sect. 1.1 do not explain, it seems, their stability. In this review we have compiled a fist of all the reported instances where the formation of stable particles was detected in aqueous solutions of neutral thermosensitive neutral polymers at elevated temperature. We present studies of homopolymers, as well as their copolymers consisting of thermosensitive fragments and ei-... 

The number of free radicals detected by EPR in porous carbons varies from 10 to 10 radicals per gram and is strongly dependent on the per cent carbon content of the carbon. Likewise in the carbonization of organic materials the number of radicals is strongly dependent on the temperature of carbonization a maximum number of radicals is attained by carbonization between 500 and 600°. Heat treatment of carbon blacks formed by pyrolysis of natural gas and oils also results in a variation 182) of the number of unpaired electrons. 

Pilling-Bedworth ratio of 1 96, anatase phase films can show cracks and fissures with, consequendy, a loss of mechanical stability, however a hydrogen reduction treatment above 600°C leads to phase transition from anatase (101) to rutile (110) [43] with XRD detecting TiH2 upon prolonged hydrogen treatment of titania. As shown in Fig. 4.4, introduction of vanadium increases the intensity of the anatase Ti02 peak above 700°C disappearance of the vanadium (001) peak and the simultaneous appearance of the rutile (110) peak are observed, but anatase continues to dominate even after heat treatment at 800° C. A sharp vanadium (001) peak is observed for heat treatments carried out in air, while no vanadium peak has been seen in the case of heat treatment at 600°C in presence of Ar/H2. 

Detection of p-lactoglobulin modification in milk samples as a consequence of heat treatments Detection of p-lactoglobulins as a marker to detect fraudulent addition of bovine milk during manufacturing of buffalo Mozzarella... 

The analysis by X-ray diffraction after catalysis showed only the presence of the a or p phase of the mixed iron and cobalt molybdates depending upon heat treatment, 380 or 430 C respectively. No phase suspected to be present in the conditions of the catalysis reaction have been detected. This was confirmed by IR spectroscopy and EPR which did not detected any new ferric species (9). 

Nitric oxide can then be detected alone or in interaction with an oxide ion to form NO (141, 143). These processes suggest that the catalytic activity of Ti02 samples is likely to depend on both preparation and heat treatment (144). From the work discussed above, there is no clear-cut evidence at present that the 02 ion can exist on oxide surfaces. 

Homozygous mutations will often be missed with this method. However, this can be overcome by supplementing the sample to be investigated with equal amounts of a sequenced sample lacking mutations. This will result in hetero duplexes formed between a mutant and the supplemented wild-type allele following the initial heat treatment and slow cooling of the PCR products. These hetero duplexes will be detected as abnormal patterns on the DHPLC. 

Detectable concentrations of various antibacterials in milk attained by different microbiological tests are presented in Table 27.2. Milk constitutes a matrix that, apart from heating to destroy natural inhibitory substances, does not generally necessitate further sample treatment. Some antibiotics, however, exhibit some instability to heat treatment (54-56) and, therefore, if further confirmation is required reference frozen samples should always be available. When raw milk is directly analyzed, critical evaluation is generally required because natural inhibitors such as somatic cells, immunoglobulins, and metabolites may cause zones of inhibition (56, 57). Furthermore, several factors including marked pH-devia-tions, use of paper disks that contain inhibitory substances, and work with forceps that are too hot or have not been cleaned properly can readily lead to falsepositive readings (56, 58). 

The data of Nilsson and Willart (1960) indicate that heating at 80°C for 20 sec is sufficient to destroy all lipases in normal milk. Their studies included assays after 48 hr of incubation following heat treatment. At lower temperatures for 20 sec, some lipolysis was detected after the 48-hr incubation period after heating. Thus, 10% residual activity remained at 73 °C. Below the temperature of 68°C the amount of residual activity was enough to render the milk rancid in 3 hr temperatures below 60 °C had no appreciable effect on lipolysis. With holding times of 30 min, 40°C produced only slight inactivation, and at 55°C 80% inactivation was reported. 

In the process of photocatalysis, the electrons and holes produced on photoirradiated Ti02 powders are trapped at the particle surface to form unpaired-electron species (step (4) in Fig.D.3). Photocatalytic reactions are actually the reactions of these radicals with reactant molecules at the Ti02 surface. Electron spin resonance (ESR) spectroscopy has been used for the detection of the photoproduced radicals on Ti02 at low temperatures such as 77 K. It has been reported that photoproduced electrons are trapped at various different sites titanium atoms on the surface or inside the particles, or oxygen molecules adsorbed on the surface. On the other hand, photoproduced holes are trapped at lattice OAygen atoms near the particle surface or at surface hydroxyl groups. We analyzed these radical species for several Ti02 photocatalysts that are commercially available, and found that the differences in the photoproduced radicals resulted from different heat-treatment conditions and the reactivity with several molecules.17)... 

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