Comparison of bactericidal efficiency of 7.5 MeV X-rays, gamma-rays, and 10 MeV e-beams
Beom‐Seok SongYun-Jong LeeByeong-Geum MoonSeon-Min GoJong‐Heum ParkJae‐Kyung KimKoo JungDongho KimSangryeol Ryu
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Food Irradiation
This study was designed to monitor some bacteriological and physical quality of milk from two dairy factories before and after pasteurization, and also to assess the compliance of this quality detected with the standard set by the Sudanese Standards and Meteorology Organization (SSMO). Two hundred and Twenty raw and pasteurized milk samples were collected from dairy factories and sale points in Khartoum State. The average total bacterial counts before pasteurization was1×10 5 -9×10 6 cfu/ml and after pasteurization it was 0-9×10 4 cfu/ml. Most of the market samples in day 1,3 and day 6 showed range of 0-1×10 4 cfu/ml. Staphylococci counts before pasteurization were found in range of less than 1×10 4 cfu/ml and after pasteurization were in the range of 0-9×10 cfu/ml. The Coliform counts before pasteurization were in the range of 1×10 3 -9×10 3 cfu/ml and immediately after pasteurization the range was reduced to 5- 1×10 2 cfu/ml. E.coli was identified from24%of the samples before pasteurization. Before pasteurization acidity was found to be 0.17%, directly after pasteurization the acidity was 0.15-0.16% but it was 0.16-0.17% in market samples.
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A study of the effect of pasteurization on goats' milk took place in order to compare the effectiveness of two pasteurization processes (low and high pasteurization) by assessing the procedure microbiologically and biochemically. The results revealed that both pasteurization processes were effective, showing microbial destruction of approximately 100%. With regard to the determination of phosphatase activity to monitor pasteurization, data in both cases were higher than the limit established for a well pasteurized milk, according to the method used. Machine milked milk showing a lower microbial content nearly achieved the standard level by batch pasteurization, 0.75 μg phenol/ml, but 2.5 μg phenol/ml by the high temperature short time (HTST) method. Phosphatase activity levels of 1.8 and 4.3 μg phenol/ml were the mean values obtained for low and high pasteurization respectively. Our results lead to the conclusion that the batch method for pasteurization of goats' milk is more efficient in terms of total bacterial count than the HTST method. Furthermore, the technique used for the determination of phosphatase activity does not seem to be adequate for pasteurization control of goats' milk, since in very rare situations were we able to attain the limit established.
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Milk is normally heat treated in order to obtain safe dairy products with an elongated shelf life as compared to raw milk. New methods, such as infusion pasteurization, for heat treatment of milk are currently being developed. This provides an opportunity for treating milk in a manner that creates different or improved functional properties compared to traditional indirect pasteurization.
Infusion pasteurization has a time-temperature profile characterized by very rapid heating to relatively high temperatures, short holding times and very rapid cooling, which may lead to products with different properties as compared to products subjected to the standard low pasteurization at 72°C for 15s.
Infusion pasteurization was performed on raw milk with two different holding times (0.1s and 0.7s) and for each holding time samples were drawn at three different temperatures (80°C, 100°C, and 120°C). Samples were compared to raw milk and to milk from the same batch subjected to a standard pasteurization at 72°C for 15s. The size of the casein micelles and the viscosity were measured in skimmed milk samples, using dynamic light scattering and capillary viscometri, respectively.
The results showed a broadening of the size distributions of the casein micelles as the temperature of the infusion pasteurization increased from 80°C to 120°C with no marked difference between the two holding times. The viscosity also increased with increasing intensity of the infusion pasteurization treatment. Little or no difference was seen between the raw milk, the standard pasteurization and the infusion treatments at 80°C regarding both casein micelle size and viscosity.
The observed changes in the investigated physical properties of the infusion pasteurization treated milk indicate that this novel pasteurization process might result in milk with altered functionality when used in the production of dairy products. This is currently under investigation.
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To facilitate establishing regulations for irradiated foods, Korean traditional soybean-based fermented powdered doenjang (PD), kanjang (PK), kochujang (PKC) and chungkukjang (PC) were irradiated at 1, 3, 5 and 7 kGy, and subjected to irradiation detection analyses as part of establishing a database for detecting irradiated foods. Photostimulated luminescence (PSL) and electron spin resonance (ESR) were applied as the detection methods. Using PSL analysis, the irradiated PD, PK and PKC could be easily distinguished from the non-irradiated ones, while irradiation of the PC at 5 kGy or higher was detectable. The ESR spectra of the irradiated PD, PK and PKC exhibited symmetrical multiplet lines, which might be induced from the crystalline sugar, whereas, the PC showed a single signal at the paramagnetic centers. The signal intensity increased with incremental increases of irradiation doses distinguishing the irradiated samples from the control. In addition, the peak height also revealed that irradiation induced an increment in the intensity of single and/or multiplet lines of the ESR signals, resulting in clear confirmation of irradiation. Thus, the data from this study could be used as references for detecting irradiated soybean-based fermented powdered sauces.
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Food Irradiation
Gamma Irradiation
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Considering the commercial use of food irradiation and the prevalence of international trade of irradiated food and agricultural commodities, black soybeans originating from China or Korea were irradiated at 0-5 kGy. Photostimulated luminescence (PSL) and thermoluminescence (TL) were investigated for their ability to identify characteristics that would distinguish irradiated from non-irradiated samples.Dried black soybeans [Glycine max (L.) Merr.] were irradiated using a Co-60 gamma irradiator or an electron-beam accelerator and then analysed by PSL and TL.PSL photon counts were higher in irradiated samples than in non-irradiated ones and increased with applied doses, making it possible to distinguish irradiated from non-irradiated samples. The TL analysis revealed glow curves (TL₁) with low intensity for non-irradiated samples but a higher intensity (approximately 200°C) for irradiated samples, showing increased intensities with radiation dose. The minerals were re-irradiated at 1 kGy and the second TL glow curve (TL₂) was measured. Based on the calculated TL ratios (TL₁/TL₂) and the shape of TL₁ glow curves, the irradiated samples could be distinguished from non-irradiated ones.PSL and TL are effective screening and reference methods for distinguishing gamma ray or electron beam irradiated black soybeans from non-irradiated black soybeans.
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1. The numbers and species of micro-organisms surviving in commercial high-temperature short-time pasteurized milks sampled direct from the cooling section of the pasteurizer have been determined and compared with those in the corresponding raw milk and in the raw milk after low-temperature pasteurization in the laboratory. 2. The geometric mean counts at 37° C. for twenty-five samples of raw, L.T. and H.T.S.T. pasteurized milks were 74,130, 1,740 and 3,200 per ml. respectively. The corresponding figures at 30° C. were 123,030, 7,080 and 8,510 per ml. 3. The percentage destruction of the bacteria was slightly smaller at all four plants for the H.T.S.T. pasteurized milks than for the corresponding L.T. pasteurized milks. The mean percentage destruction for the L.T. pasteurized milks was 97·7% for bacteria growing at 37° C. and 94·3% for bacteria growing at 30° C. The corresponding figures for the H.T.S.T. pasteurized milks were 95·9 and 93·1%.
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Summary The keeping quality (KQ) of whole milks pasteurized at 72 °C, 78 °C or 83 °C for 20 s and stored at 12 or 7 °C was examined by assessment of the naturally contaminating thermoduric microflora and of the numbers of Gram-negative rods, a single strain of the latter being introduced deliberately by post pasteurization inoculation. A pasteurization temperature of 83 °C reduced the KQ at 7 °C by about 15% compared with pasteurization at 72 °C or 78 °C, with a 2 d loss in the absence, and aid loss in the presence, of the post pasteurization contamination. The KQ of milks stored at 12 °C was not significantly affected by the pasteurization temperature. Milks pasteurized at 78 °C tended to have a slightly better KQ than those pasteurized at 72 °C, especially at 7 °C. However, pasteurization at both 78 °C and 83 °C caused a reduction in cream rising and considerably increased the risk of cream plugging.
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