Viscosity and Specific Heat of Vegetable Oils as a Function of Temperature: 35°C to 180°C

The viscosities and specific heat capacities of twelve vegetable oils were experimentally determined as a function of temperature (35 to 180°?C) by means of a temperature controlled rheometer and differential scanning calorimeter (DSC). Viscosities of the oil samples decreased exponentially with temperature. Out of the three models (modified WLF, power law, and Arrhenius) that were used to describe the effect of temperature on viscosity, the modified WLF model gave the best fit. The specific heat capacity of the oil samples however increased linearly with increase in temperature. The equations developed in the study could be valuable for designing or evaluating handling and processing systems and equipment that are involved in the storage, handling and utilization of vegetable oils.     

Spores of Bacillus cereus strain KBAB4 produced at 10 °C and 30 °C display variations in their properties

Spores of the psychrotrophic Bacillus cereus KBAB4 strain were produced at 10 °C and 30 °C in fermentors. Spores produced at 30 °C were more resistant to wet heat at 85 °C, 1 % glutaraldehyde, 5 % hydrogen peroxide, 1 M NaOH and pulsed light at fluences between 0.5 and 1.75 J cm⁻² and to a lesser extent to monochromatic UV-C at 254 nm. No difference in resistance to 0.25 mM formaldehyde, 1 M nitrous acid and 0.025 g l⁻¹ calcium hypochlorite was observed. Spores produced at 10 °C germinated more efficiently with 10 mM and 100 mM l-alanine than spores produced at 30 °C, while no difference in germination was observed with inosine. Dipicolinic acid (DPA) content in the spore was significantly higher for spores prepared at 30 °C. Composition of certain fatty acids varied significantly between spores produced at 10 °C and 30 °C.     

Effect of prolonged heat treatment from 48 °C to 63 °C on toughness, cooking loss and color of pork

The effect of low temperature long time (LTLT) heat treatment at 48 °C, 53 °C, 58 °C, and 63 °C for T(c) (time to reach a core temperature equal to the water bath), T(c)+5h holding time, and T(c)+17h holding time was studied in Longissimus dorsi and Semitendinosus muscles from slaughter pigs and sows. Meat toughness (Warner-Bratzler Shear Force), cooking loss and color (Minolta L*a*b*-values) was measured and in the cooking loss the amount of heat-soluble collagen and activity of cathepsin B+L was determined. Decreasing shear force and increasing cooking loss during LTLT treatment was observed between 53 °C and 58 °C. Furthermore, increasing temperature from 53 °C to 58 °C and increasing time from T(c) to T(c)+17h increased the solubility of collagen. Residual activity of cathepsin B+L in LTLT treated pork was mainly affected by temperature, showing the highest activity at 58 °C and 63 °C.     

Detection of specific spoilage bacteria from fish stored at low (0°C) and high (20°C) temperatures

The spoilage potential of 309 bacterial strains isolated from fish spoiled at 0 and 20°C was investigated. Gram-negative, non-fermentative, motile rods tentatively identified as Alteromonas were the major spoilage organisms at 0°C. These bacteria were also found at 20°C, but a large number of Gram-negative, fermentative, motile rods belonging to the Vibrionaceae were also identifieas spoilage organisms at this temperature. Most of the Vibrionaceae did, however, not produce hydrogen sulphide from thio-sulphate but only from the sulphur containing amino acid, L-cysteine. A specific count of fish spoilage organisms at both low and high temperatures could therefore be obtained directly on an Iron Agar containing thiosulphate and cysteine where bacteria capable of forming H₂S from either source of sulphur would appear as black colonies.     

A comparison of the effects of storage of raw milk at 2°C and 6°C on the yield and quality of Cheddar cheese

The advantages of storing raw milk, which is to be used for Cheddar cheese manufacture, at 2°C rather than at 6°C was examined. Storage of milk at the lower temperature effectively reduced the level of psychrotroph growth, and after 4 days the psychrotroph counts in samples stored at 2°C were 100-fold lower than those found in samples stored at 6°C. There was no advantage in terms of cheese yield in storing milks at the lower temperature, but an overall improvement in cheese quality was noted in samples produced from milk stored at 2°C.     

Liberation of actin from actomyosin in meats heated to 65°C

This study investigated whether actin liberation from myofibrils occurs during the heating of various muscles, as well as squid mantle muscle at temperatures, such as 60°C, employed for vacuum cooking of meats. Actin liberation was demonstrated in scallop striated adductor muscle, but not in beef, pork, or chicken, using the detection method previously employed with squid muscle, in which liberated actin was detected with SDS-PAGE, in the supernatant obtained by centrifugation of the homogenate of heated muscle in 0.2M KCl at a neutral pH. However, actin liberation was demonstrated in beef, pork and chicken by a new detection method, in which heated muscle was homogenized in 0.6M KCl or NaCl at a slightly alkaline pH and maintained at 4°C for 16h with stirring, after which the homogenate was diluted three times with water and centrifuged to obtain the supernatant containing the liberated actin. This new method indicated that actin liberation in beef, pork, and chicken was marked by heating at 65°C, but scarcely induced at 80°C. Thus, the liberation of actin from myofibrils may contribute to the greater tenderness of vacuum-cooked meat (meat heated at a low temperature for long time), as compared with meat prepared by cooking at a higher temperature.     

Quality changes of ready-to-eat ginseng chicken porridge during storage at 25°C

Ready-to-eat (RTE) ginseng chicken porridge was heated in a retort with an F-value of 4.0 after being packaged in a gas-tight plastic tray (PP/EVOH/PP) with top film (PET/PA/CPP). Various quality changes were investigated during the storage for 28weeks at 25°C. Over the storage period, microorganisms were not detected above 1.0 log cfu/cm(2) (detection limit). The viscosity increased sharply from 775 to 2025cp for initial 4weeks and increased steadily until 16weeks, with a slight reduction thereafter. During the 28weeks of storage, the ratio of residual oxygen and pH decreased from 10.8% and 6.49 to 5.7% and 6.05, while retrogradation degree increased from 0% to 55.9%. Hunter L(?), b(?), and ΔE values increased until 20weeks and remained for the rest of storage. Based on sensory, microbiological and physicochemical evaluations, the RTE ginseng chicken porridge could be marketable for at least 24weeks at 25°C.     

Histamine stability in Rihaakuru at -80, 4 and 30°C

Rihaakuru is a shelf stable fish paste product formed from a fish soup prepared from tuna. Histamine contamination is a food safety issue with this product that is manufactured from tuna fish that has been temperature abused. Histamine concentrations decreased between 31% and 73% in Rihaakuru stored for 10months at either -80, 4 or 30°C. This appears to be a property of the product as histamine solutions are reported to be stable, at least under frozen storage. The risk of histamine food poisoning due to Rihaakuru may reduce during the storage of the product.     

Some structural properties of ovalbumin heated at 80°C in the dry state

Dry heating of ovalbumin at 80°C improved the gel properties, including the gel strengthening and transparency upon the subsequent heating for gelation [Matsudomi, N., Ishimura, Y., & Kato, A., (1991). Improvement of gelling properties of ovalbumin by heating in dry state. Agricultural and Biological Chemistry, 55, 879–881.]. Some structural properties of the dry-heated ovalbumin responsible for such gel properties were studied. The electrophoretic patterns revealed the formation of ovalbumin polymer through hydrophobic and disulfide protein-protein interaction during heating in the dry state. The slight changes in circular dichroism spectrum and surface hydrophobicity indicated mild conformational changes in ovalbumin molecules. Differential scanning calorimetry themograms showed that enthalpy of denaturation of ovalbumin was markedly decreased with an increase of dry-heating time. The deamidation of ovalbumin was found to occur during the dry-heating process, and the degree of deamidation reached 10% after dry heating at 80°C for 7 days. It was assumed that the partially unfolded and deamidated ovalbumin produced by the dry heating forms specific soluble aggregates during subsequent heating for gelation, resulting in the formation of an ordered gel matrix.     

Effect of a 10-day ageing at 30°C on the texture of dry-cured hams processed at temperatures up to 18°C in relation to raw meat pH and salting time

The aim of this study was to investigate the effect of a 10-day ageing at 30 ± 2 °C on the texture of dry-cured hams processed at temperatures up to 18 ± 2 °C for 12 months in relation with raw ham pH and salting time. Three pH groups (semimembranosus muscle at 24 h post-mortem: Low pH < 5.7, Medium pH = 5.7  pH  5.9, and High pH > 5.9), three salting times (6 d, 10 d and 14 d) and two ageing temperatures (18 °C and 30 °C) were investigated. Physicochemical characteristics, instrumental and sensory texture and product sliceability were evaluated on biceps femoris and semimembranosus muscles. Hams with pH_SM24 < 5.7 should be avoided in order to reduce the incidence of texture problems in dry-cured ham elaboration. Texture problems are especially important in hams with a reduced salt content that are mechanically sliced (not frozen). A 10-day ageing at 30 °C could be useful for reducing the soft texture problems in dry-cured hams processed at temperatures up to 18 °C for 12 months without affecting the product flavour.     

Effect of muscle restraint on sheep meat tenderness with rigor mortis at 18°C

The effect on shear force of skeletal restraint and removing muscles from lamb m. longissimus thoracis et lumborum (LT) immediately after slaughter and electrical stimulation was undertaken at a rigor temperature of 18°C (n=15). The temperature of 18°C was achieved through chilling of electrically stimulated sheep carcasses in air at 12°C, air flow 1-1.5 ms(-2). In other groups, the muscle was removed at 2.5 h post-mortem and either wrapped or left non-wrapped before being placed back on the carcass to follow carcass cooling regimes. Following rigor mortis, the meat was aged for 0, 16, 40 and 65 h at 15°C and frozen. For the non-stimulated samples, the meat was aged for 0, 12, 36 and 60 h before being frozen. The frozen meat was cooked to 75°C in an 85°C water bath and shear force values obtained from a 1 × 1 cm cross-section. Commencement of ageing was considered to take place at rigor mortis and this was taken as zero aged meat. There were no significant differences in the rate of tenderisation and initial shear force for all treatments. The 23% cook loss was similar for all wrapped and non-wrapped situations and the values decreased slightly with longer ageing durations. Wrapping was shown to mimic meat left intact on the carcass, as it prevented significant prerigor shortening. Such techniques allows muscles to be removed and placed in a controlled temperature environment to enable precise studies of ageing processes.     

槽筒车6°改为9°15′的方法

目前各地针织厂的槽筒车,大都采用 GO66或1332型,其木筒管倾斜度均为6°,倒纱后的引纱退绕张力较大,影响织造布面清晰度。因此,必须改变倾斜度,即把6°改为9°15′。有的单位,采取更换握臂,锭头、锭杆、锭管。来达到9~015′纸箔筒管     

60°和120°复合刀具的设计与制造

本文介绍60°和120°复合刀具的设计与制造.     

360°全景照相机

美国哥伦比亚大学的研究人员发现了一种可使变形景像恢复原状的方法，从而发明了一种全景照相机"Omnlcam。实现全景拍摄的照相机采用了一个抛物状的反射镜，其特殊的形状可使所有从景物L反射出的光线在进人相机时都经过同一个点。这是鱼眼镜头或反射镜无法做到的。一旦景像被适当地摄人并存储在计算机中，视野中的任何一点都可利用软件来重新构成。全景相机的研制者纳雅预计，将来这种相机在召开电话会议、监测、体育和新闻广播及为机器人安装"眼睛"等方面将得到广泛应用。##F37360°全景照相机     

360°随意空间

身为某知名网站高管的主人,一个人私享着北京玫瑰园这套280平方米的双拼别墅。主人对居家设计的看法,被设计师张志宽如此总结了下来:"设计不纯粹是视觉上的模拟某种风格,更核心的是它所指向的生活方式以及视觉效果所呈现出     

仰望桑果37°

37°是仰望的角度,只有面对高度,我们才会仰望,比如月亮——我在仰望,然而在这世界上,还有桑果在让我仰望。桑果是一种果实,在烹饪世界,我们可以见到桑果汁、桑果露酒、桑果冻、桑果酱……它们由点到线,由线及面,展示出的是一个立体的桑果世界。食客说:桑果系列,一个都不能少。营养师说:桑果,     

Determination of biogenic amines in fresh unpacked and vacuum-packed beef during storage at 4°C

Biogenic amines, putrescine, cadaverine, and histamine were determined in unpacked and vacuum-packed beef; during storage at 4°C for 12 and 35 days, respectively, under the same conditions. Analysis by High Performance Liquid Chromatography in both kind of samples, showed variation of cadaverine and histamine with an increasing tendency to a definite increase of putrescine. In unpacked samples, maximum mean contents for each amine reached 10.4, 5.2 μg/g for putrescine and cadaverine, respectively (12th day) and 2.2 μg/g for histamine (5th day). The total amine content reached 16.5 μg/g (12th day). After 8 days of storage, organoleptic fall-off began and, on the 12th day, all samples were disqualified. In vacuum packs, amine levels increased after 19 days. Maximum levels were determined for putrescine on the 35th day (36.3 μg/g), for cadaverine on the 26th day (28.9 μg/g) and for histamine on the 35th day (19.0 μg/g). Although the vacuum-packed beef was organoleptically acceptable up to 35 days, the total amine levels were greater than 5 μg/g after the 12th day, indicating a leveling off of quality.     

Quality changes and shelf life of imported vacuum-packaged beef chuck during storage at 0°C

The objective of this study was to investigate differences in adipose tissue fatty acid composition among stress genotypes as well as to determine relationships of those fatty acids with performance, carcass and meat quality traits. Haplotypic analysis of parents and offspring was employed to assign 48 pigs to three stress genotypes of swine. Individual fatty acid profiles were determined on subcutaneous backfat. Stress genotype had a significant effect on the proportions of C14:0 (P<0.05), C16:0 (P<0.10), C16:1 (P<0.05) and C18:0 (P<0.05) fatty acids. After adjusting for stress and gender, there was a negative correlation between backfat thickness and essential fatty acids (linoleic and linolenic) (P<0.001). In contrast, the correlation of loin muscle area with C18:2 (P<0.01) and C18:3 (P<0.001) was positive. The degree of fat firmness was negatively correlated to the proportion of total unsaturated fatty acids (P<0.01). No significant correlations were observed between fatty acid contents and lean meat quality traits.     

Effect of chemical dips on unchilled fresh beef inoculated with E. coli, S. aureus, S. faecalis and Cl. perfringens and Stored at 30°C and 20°C

The antimicrobial effect of three chemical dips (A: potassium sorbate, 20g; sodium acetate, 5g; sodium chloride, 5g; water, 100 ml. B: potassium sorbate, 20g; sodium acetate, 5g; sodium chloride, 5g; propylene glycol, 20 ml; glycerol, 10 ml; water, 70 ml and 0·5N NaOH to pH 10. C: potassium sorbate, 10 g; sodium acetate, 10 g; sodium citrate, 10g; sodium chloride, 5g; water, 100 ml and 0·5N NaOH to pH 10) on unchilled f resh beef samples inoculated with E. coli, S. aureus, S. faecalis and Cl. perfringens and stored at 30°C and 20 °C was investigated. Treatments had produced a significant (P < 0·01) inhibitory effect on all the organisms inoculated, with a reduction of about 3 to 5 log units compared with the control. pH changes were comparable with the control at 5°C. No significant differences were found between the treatments and shelf life could be extended up to 44 h at 30°C and 68 h at 20°C whilst, in the control, visual spoilage and high bacterial counts were observed by 20h at 30°C and by 20 to 32h at 20°C. Treatment C, containing potassium sorbate at a low level (10%), was considered better than treatments A and B since potassium sorbate at higher levels had produced slight off-odours without a greater inhibitory effect.