Effects of frying and storage on cholesterol oxidation in minced meat products

The presence of cholesterol oxidation products (COP) in the diet is a health concern for their various known adverse effects. It is important that the generation of COP be assessed during different stages of production, handling, and storage of meats and meat products so that relevant measures can be taken to minimize the production of COP. In a preliminary study, we investigated the content of COP in the lipids of raw meatballs (50% prok+50% beef), prefried meatballs (50% pork +50% beef), raw hamburger (100% beef), and prefried burger (50% pork+50% beef). Six of the common COP, viz 7α- and 7β-hydroxycholesterol, 7-ketocholesterol, 5α,6α-epoxycholestanol, 5β,6β-epoxycholestanol, and cholestanetriol, were analyzed by gas chromatography (GC) and GC-mass spectroscopy. The total content of these COP was in the range of 7 to 10 μg/g lipids in raw meatballs, prefried meat balls, and raw hamburger, after frying these samples for consumption. The prefried hamburger had ca. 8μg/g lipids of the total COP before frying, and this amount increased to 29 μg/g lipids after frying. During the storage of this fried sample, the total COP increased to 42 and 50 μg/g lipids, after 1 and 2 wk of storage, respectively. The results of this study show that freshly prepared meat products are a minor source of COP in the diet. However, if semiprepared frozen meat products are fried once and then stored for future consumption, the levels of COP can increase considerably, and this may be of concern for certain groups of consumers. Presented in part as a poster at the 88th AOCS Annual Meeting and Exposeattle, WA, May 11–14, 1997.     

Antioxidant properties of tomato lipids

Summary Highly active antioxidants for lard were extracted from dried tomato fruits with petroleum ether. When added to fresh lard, the tomato lipids protected against autoxidation at 100°C. for long periods with little accumulation of peroxides during the induction period. When added at a 2% level to actively oxidizing lard (peroxide values 20 to 130), the tomato lipids effected a rapid drop of approximately 25% in titrable peroxides. When added at a level of 8%, this immediate drop was followed by a second, more gradual, drop to a constant low value (ca. 5), which was maintained for a long period at 100°C. The antioxidant activity of the tomato lipids was separated into two fractions, one consisting of a primary antioxidant and the other of a synergistic (potentiating) substance. The primary antioxidant activity was accountable in the tocopherol content of the extracts. The synergistic activity was qualitatively similar to phosphoric acid, and the synergistic fraction was found to contain 2.4% phosphorus. However solubility data indicated the phosphorus was present in an organic form, probably phosphatides. Journal Paper No. 990 of the Purdue Uniersity Agricultural Experiment Station. The subject-matter of this paper was undertaken initially in cooperation with the Committee on Food Research of the Quartermaster Food and Container Institute for the arned firces. The opinions r conclusions contained in this report are those of the authors. They are not to be construed as necessarily reflecting the views or endorsements of the sponsor.     

固相萃取-流动注射-化学发光法测定鸡饲料和鸡肉中的氯霉素

基于氯霉素与铬(Ⅵ)的氧化-还原反应所产生的铬(Ⅲ)催化Luminol(鲁米诺)-过氧化氢化学发光体系的研究,样品中氯霉素采用液乙酸乙酯提取,固相萃取净化,结合流动注射技术和化学发光检测,建立了一种高灵敏度的快速测定鸡饲料和鸡肉中氯霉素的新方法。方法线性范围为0.03～5mg/mL和0.04～5μg/mL,方法检出限为0.03mg/kg和0.05μg/kg,平均回收率>75%,RSD为11.2%和15.4%(饲料:2.0mg/kg;鸡肉:0.5μg/kg,n=11)。     

Heat transfer and drying kinetics of tomato pulp processed by cast-tape drying

Cast-tape drying (CTD) is a process to dehydrate suspensions. This study evaluated the influence of heat source and forced air convection on the drying rate and temperature of tomato pulp during CTD. To this, a pulp thin layer was spread on a flexible support with its lower surface in direct contact with a heat source. Similar drying rates and evaporative capacities were observed for both flexible supports and heating media. Steam simplifies the temperature control and equipment construction. CTD is a suitable process for producing dried tomato pulp in short drying times, resulting from high evaporative capacity.     

Effluent treatment of industrial wastewater using processed solid residue of olive mill products and commercial activated carbon

The carbonised solid residue of olive mill products, called J-carbon (0·6–0·7 mm), was compared with Sigma activated carbon (powder) and Chemviron activated carbon (0·6–0·7 mm) in treatment of the effluent of Flexsys' wastewater. The removal of NH₃, TOC as non-specific organics, and six specific leading organic pollutants from Flexsys' wastewater effluent were examined. All three different carbon sources have almost similar behaviour in removing the above pollutants; the removal efficiencies were as follows: Sigma carbon: benzothiazole, 1,2-dihydro-2,2,4-trimethylquinoline, N-dimorpholinyl ketone, methylsulphyl benzothiazole and methyl-2-benzothiazole sulphone 100%>TOC 94%>NH₃ 82%>tetrachloroethene 50%. Chemviron carbon: benzothiazole, 1,2-dihydro-2,2,4-trimethylquinoline, N-dimorpholinyl ketone, methylsulphyl benzothiazole and methyl-2-benzothiazole sulphone 100%>NH₃ 87%>TOC 40%>tetrachloroethene 31%. J-carbon: benzothiazole, methylsulphyl benzothiazole and methyl-2-benzothiazole sulphone 100%>NH₃ 78%>1,2-dihydro-2,2,4-trimethylquinoline 70%>tetrachloroethene 58%>N-dimorpholinyl ketone 50%>TOC 37%. © 1998 SCI     

Antioxidant activity of sodium nitrite in meat

Polar lipids were extracted from raw, nitrite-treated beef and pork by a dry column procedure. The polar-lipid fraction had substantial activity in inhibiting the oxidation of linoleic acid as determined by a β-carotene bleaching method and by conjugated diene formation. The antioxidant activity of the polar-lipid fraction was stable over several months when stored in hexane at−20 C. Residual sodium nitrite, carbon-nitroso and nitrogen-nitroso compounds or products of the addition of nitrogen oxides to olefins do not seem to account for the antioxidant activity observed.     

Characterization of pellets from industrial tomato residues

Large volumes of residual biomass (mainly peels and seeds) are generated by tomato industrial processing plants. After adequate drying and densification operations, those biomass wastes might be used for livestock food production, for lycopene extraction or even as fuel supply for thermal applications.The process described in the present paper is the manufacturing of 6 mm diameter pellets from tomato waste samples obtained from industrial processing plants. As a previous step, the samples were dehydrated to five different values of moisture content (20, 25, 29, 34 and 38 wt% w.b. approximately). Bulk and particle densities, hardness and durability of pellets were significantly influenced by the initial moisture content of the biomass raw materials, as well as by the subsequent reductions of such moisture content after pelletizing operations and storage periods. Increases of 21%, 41% and 67% in moisture content of the feeding biomass material – with respect to the lower value of the operating range, i.e. 20 wt% w.b. – were observed to yield the following percentage increments in a series of physical properties of pellets, respectively: 14%, 25% and 50% in bulk density; 6%, 16% and 18% in particle density; 225%, 1737% and 3575% in hardness; 8%, 44% and 88% in durability. Nevertheless, higher increments in moisture content of feeding material led to significantly lower values of the aforementioned properties – not to mention technical operating problems due to roller skidding in the pelletizing device.Pellets obtained from raw biomass (peels and seeds) with 34 wt% initial moisture content (9% final moisture content of pellets) were regarded as those with the most suitable configuration: durability 91.2%, hardness up to 88 N and energy density approaching 8 GJ/m³.     

Oxidative stability of fermented meat products

Meat and meat products, which form a major part of our diet, are very susceptible to quality changes resulting from oxidative processes. Quality of fermented food products depends on the course of various physicochemical and biochemical processes. Oxidation of meat components in raw ripening products may be the result of enzymatic changes occurring as a result of activity of enzymes originating in tissues and microorganisms, as well as lipid peroxidation by free radicals. Primary and secondary products of lipid oxidation are extremely reactive and react with other components of meat, changing their physical and chemical properties. Oxidised proteins take on a yellowish, red through brown hue. Products of lipid and protein degradation create a specific flavour and aroma ; furthermore, toxic substances (such as biogenic amines or new substances) are formed as a result of interactions between meat components, e.g. protein-lipid or protein-protein combinations, as well as transverse bonds in protein structures. Oxidation of meat components in raw ripening products is a particularly difficult process. On the one hand it is essential, since the enzymatic and non-enzymatic lipid oxidation creates flavour and aroma compounds characteristic for ripening products; on the other hand excessive amounts or transformations of those compounds may cause the fermented meat product to become a risk to health.     

ICS-90测定肉制品中亚硝酸盐

介绍了用离子色谱测定肉制品中亚硝酸盐的方法。实验证明,该方法在0．00mg/L-0．20mg／n呈现良好的线性关系,相关系数为0．9998,回收率为94．3％,保留时间和峰面积的相对标准偏差（RSD）分别为0．38％和2．90％。     

Microstructural changes of processed vitrified solid waste products

Toxic lead-rich solid industrial wastes were stabilized by the vitrification method. Vitrification was attained by the addition of SiO₂ and Na₂O as vitrifying and melting agent, respectively. The non-toxic, homogeneous, vitreous products studied in the present work, contain 60 wt.% of solid waste. Products with such a high content of solid waste comprise an economically realistic suggestion, but are easily devitrified in conditions of large-scale production due to the difficulty to achieve rapid cooling conditions in the whole volume of a large piece of stabilized product. Thus, it must be ascertained that the loss of homogeneity is not accompanied with the loss of chemical stability. Differential Thermal Analysis (DTA) was applied in order to inspect the prospect to crystal phase separation. The separated crystal phases were characterized by X-ray diffraction and transmission electron microscopy. Possible devitrification processes are investigated in order to interconnect the microstructure with the chemical stability of the devitrified products.     

Use of vegetable protein in processed seafood products

In comparison to other muscle foods like red meats, utilization of vegetable protein products in seafood is limited, and can be considered to be in its infancy. The opportunities are not predicated entirely on the future. Opportunities exist today, and vegetable protein products such as soy can and will impact on the seafood market. The opportunities for soy protein products in seafood are and will be realized in terms of nutrition, functionality, and economics. The change in price of frozen fish paste caused by the influence of the 200-mile zones was 2 to 2.5 times in one year. In contrast, the price of soy protein products has not changed during the same period. Obviously, this price difference has an important impact on the demand for soy protein products. As the price of fish in Japan has risen, consumers have tended to avoid buying fish products, and there has been a trend toward buying animal products. Consequently, the use of textured soy proteins in these animal protein foods has also increased. Japan has a long and well developed tradition of eating soybean foods, and at the same time, Japan possesses a high level of scientific technology concerned with new soy protein foods. The whole nation, including the consumers, producers, academic societies and the government, is of the consensus that soybeans are a good food source whose consumption should be encouraged and increased. In spite of such favored conditions, utilization of soy protein foods in Japan has not really taken off even after almost 20 years of development. Reasons for the slow expansion of the market are many. However, the definite factor which decisively affects the increased use seems ultimately to be a balance between the quality and price of the products. In Japan the balance would become favorable to soy protein because of the limited fish resources as well as recent advances in the technology of soy protein foods. Several formulations for fish/soy products are presented.     

气相色谱法测定鸡肉中二硝甲酚的残留量

本文研究了鸡肉中二硝甲酚残留量的气相色谱测定方法。样品中二硝甲酚用丙酮提取，经重氮甲烷甲基化和氟罗里硅土柱净化一，采用BP21石英毛细管柱于气相色谱仪进行测定。本实验采用添加法测定回收率，添加水平为0.02-0.2mg/kg时，其平均回收率为84.6%-89.5%。本方法的最低检出限为测定0.02mg/kg。     

Characterisation of industrial tomato by-products from infrared drying process

The thin-layer infrared drying behaviour of industrial tomato residues, peels and seeds, was experimentally investigated in the temperature range from 100 °C to 160 °C. The drying rate was found to increase with temperature, hence reducing the total drying time. In particular, as drying temperature was raised from 100 °C up to 160 °C, the time period needed to reduce the moisture content of the sample from 236.70 wt% down to 5.26 wt% (dry basis) was observed to decrease from 99.5 min to 35 min.Using a non-linear regression (Marquart's method) together with a multiple regression analysis, a mathematical model for the thin-layer infrared drying process of industrial tomato residues was proposed. The effective moisture diffusivity is dependent on moisture content; the average values for the diffusivity coefficients at each temperature were obtained using Fick's second law of diffusion, and varied from 5.179 × 10^?9 m²/s to 1.429 × 10^?8 m²/s over the temperature range. The temperature dependence of the effective diffusivity coefficient was described following an Arrhenius-type relationship. Activation energy for the moisture diffusion was determined as 22.23 kJ/mol.     

Antioxidant activity of polar lipids from nitrite-treated cooked and processed meats

Polar lipids having considerable antioxidant effect on linoleic acid have been isolated from nitrite-treated, laboratory-cooked ground pork and beef during and after four weeks’ storage at 4 C. The antioxidant activity of these polar lipids is 1.5–3 times greater than that of untreated meats. Antioxidatively active polar lipids have also been found in commercially processed, nitrite-containing meats, including pepperoni, ham, frankfurters and bacon. The antioxidant activity of active polar lipids was stable on storage and partially survived treatment with acids and bases and conversion to methyl esters. Separation of the active polar lipids or the active methyl esters by classes gave no fraction in which the antioxidant activity was highly concentrated; however, it seemed to be more highly associated with the polyunsaturates fraction of the methyl esters. Indications are that more than one antioxidant factor is involved and that at least one is associated with the acyl portion of the polar lipids.     

工业污水池的腐蚀与防护

本文就常见的工业污水处理池的防腐蚀技术进行了总结和探讨,其中对玻璃钢材里工艺的树脂材料的选择进行了讨论,结合目前防腐蚀技术的发展,推荐了一种新型材料——玻璃鳞片胶泥。