聚酯生产工艺条件优化的实践与探析

2×30kt/a纤维级聚酯生产设备和技术是从瑞士EMS—Inventa公司引进,原工艺特点是酯化压力较高、酯化I温度较低、缩聚温度高、总停留时间短等。这样,产品质量虽也能达到较好指标,但真空系统污染严重,缩聚Ⅲ液位控制不稳定,产品质量较难保证均匀。因此,在提高酯化率和缓和终缩反应条件等方面作了调整。工艺调整后,消耗指标小于合同指标,产品月合格品率达99.99％。     

CHEMICAL AND PHYSICAL CHANGES IN IRRADIATED AND FROZEN BOMBAY DUCK

SUMMARY— Bombay duck (Harpodon nehereus), a tropical fish, is readily susceptible to drip losses leading to textural alterations. These changes occur during storage at 0 or −20°C for 3 days and also by irradiation and storage at 0 or 10°C for 3 days. In situ denaturation of fibrillar proteins of Bombay duck occurs as evidenced by a decrease in salt-soluble proteins. Loss in extractability occurring at 0 or −20°C parallels increased drip loss, but appears to be arrested by pre-dip treatment in 10% sodium tripolyphosphate solution for 15 min. The radiation-induced drip loss also correlates with loss in the extractability at a radiation dose of 3 Mrad, but at 0.5 Mrad the drip loss occurs without appreciable decrease in the extractability. Pre-dip treatment in 10% sodium tripolyphosphate solution reduces the drip loss caused by 3 Mrad, but this is not reflected in the recovery of extractable proteins. Loss in the extractability could be attributed to the aggregation phenomenon of fibrillar proteins induced by irradiation. The radiation-induced off-odors appear to originate from the sarcoplasmic proteins.     

两种干酪在成熟过程中理化性质变化

对鹰嘴豆复合干酪与牛乳干酪成熟过程中的理化性质变化进行研究.通过对比试验,得出以下结论:两种干酪在成熟过程中水分含量均呈下降趋势,复合干酪的水分含量高于牛乳干酪;脂肪、蛋白质含量和酸度均呈缓慢增加趋势,复合干酪的脂肪、蛋白质含量及酸度均低于牛乳干酪.     

INCREASES IN THE DIELECTRIC CONSTANTS OF SOYBEAN AND SUNFLOWER OILS AND PRODUCT QUALITY CHANGES OF POTATOES DURING INTERRUPTED DEEP FAT FRYING1

During a 32 h interrupted period of heat processing French fries, the rate of change in the dielectric constants of soybean and sunflower oils was determined. Selected quality parameters (moisture, yield, texture, food energy) were also measured during this period. Heat processing conditions simulated good operational practices for deep fat frying within a commercial setting. The dielectric constant of sunflower increased at a significantly greater rate than soybean oil, indicating increased rates of oil deterioration. Moisture content and yield of the French fries did not differ throughout the 32 h period. Mean texture values (force) were 661 and 643 g for soybean and sunflower oil, respectively. Significant linear interactions among oil and time were found for texture. The food energy content (Kcal/g; dry basis) of French fries heat processed in sunflower oil was significantly lower than those, in soybean oil.     

水解植物蛋白生产中的化学变化及其对品质的影响

论述了酸水解法生产水解植物蛋白(HVP)中发生的化学变化,指出了HVP呈色、呈味以及有害物质的来源,并提出改善的措施.     

PHYSICAL AND CHEMICAL CHANGES IN VACUUM PACKAGED PARMIGIANO REGGIANO CHEESE DURING STORAGE AT 25, 2 AND −25C

Parmigiano Reggiano (PR) cheese, packed in single 20g portions under vacuum, was stored at three different temperatures (25C, 2C and ?25C) to evaluate chemical and physical changes in the product during 120 days of storage. There was no increase in lipid oxidation, even though the presence of pentane in the head space showed that the PR samples were already slightly oxidized following the 18 months of ripening process. Color and water activity determinations led to the hypothesis that the lipid fraction migrated to the sample surface when stored at 25C. Other changes observed by the authors influenced the modification of the flavor and a decrease in the overall acceptance of the PR samples packed under vacuum and stored at room temperature. However, they did not seem to be related to lipid oxidation.     

CHANGES IN BIOGENIC AMINES OF MAJOR PORTUGUESE BLUEFISH SPECIES DURING STORAGE AT DIFFERENT TEMPERATURES

Changes in histamine (Him), cadaverine (Cad), putrescine (Put), agmantine (Agm) and volatile basic nitrogen (VBN) contents were examined in sardine, Atlantic horse mackerel, chub mackerel and Atlantic mackerel, during ice storage and storage at room temperature. Him formation as well as other amines varied greatly with species of fish and storage conditions. The levels of Him, Cad, Put and VBN increased gradually in all the fish species as decomposition progressed, regardless of storage temperatures. In iced fish, amine production was considerably reduced and Him concentration was, in general, lower than 100 mg/Kg. During ice storage amines increased slowly until day 7, after which a significant rise was detected. In comparison with the other fish species higher levels of Him, Cad and Put were determined in Atlantic mackerel. At room temperature Him, Cad and Put were produced at the highest concentrations in chub mackerel, followed by sardine, Atlantic mackerel and Atlantic horse mackerel. Him concentration maximum exceeded allowable limits for human consumption in the first three species after 24h of storage at room temperature. No correlation was observed for Him or other amine levels and the degree of fish decomposition. Thus, the use of Him or other amines as a freshness index of the studied fish species was not considered appropriate.     

STUDIES ON BARLEY AND MALT WITH THE RAPID VISCOANALYSER: [I] THE EFFECT OF VARIATIONS IN PHYSICAL AND CHEMICAL PARAMETERS

Rapid Viscoanalysis was investigated as a method off determining the malting quality of barley and malt, to define the conditions required to select progeny with high malting potential from a barley breeding programme. Studies were made on (i) varying physical parameters and chemical additions, (ii) the effect of modification, (iii) the prediction of malting potential from viscograms, (iv) the relationship of the viscometric characteristics of starch to malting quality and (v) the use of a Rapid Viscoanalyser (RVA) in a commercial meltings. The results will be presented as a series of papers. In this paper, physical and chemical factors were examined. Firstly, sample/liquid ratios, initial and final temperatures, speed off mixing and the fineness of grinding of the samples were varied. The effect of the time of standing of malt slurries was also investigated. The peak areas, peak viscosities and Stirring Numbers were shown to obey a relationship with the cube of the sample concentration under a wide range of conditions. Comparisons with the Amylograph and Falling Number Apparatus are reported. Conditions of grinding, temperature, speed of mixing and grist/liquid ratios for the routine examination of barleys and malts were defined. Secondly, calcium-complexing agents, acids, alkalies and the salts of heavy metals were tested for their effects on the Rapid Viscogram of malt. Unless substantial time was allowed for reaction to occur, calcium-complexing agents per se had no effect on viscograms: acidic radicles were necessary. Although both acids and alkalies affected viscograms, inhibition could be reversed by neutralisation. Silver nitrate is suggested as the most suitable chemical for inhibition of enzymes for the determination of the intrinsic viscosity of malts with an RVA.     

CHANGES IN MAJOR ANTIOXIDANT COMPOUNDS DURING AGING OF TRADITIONAL BALSAMIC VINEGAR

Traditional balsamic vinegar (TBV) shows antioxidant capacity that increases passing from cask 5, containing the youngest vinegar, to cask 1 containing the oldest vinegar. This increase in antioxidant capacity is a consequence of both the concentration of compounds already present and of new antioxidants formation and is positively related to the increase in the polyphenolic content and in the Maillard reaction/caramellization products. During TBV aging, some reactions involving flavonoids and tannins take place. Tannins can undergo acid-catalyzed cleavage of their interflavonoid bonds with subsequent condensation of other flavonoid molecules. In addition, the low pH, the decrease of the water content and the presence of aldehydes, may promote flavonoids polycondensation. These reactions explain the observed increase in polymeric phenolic compounds and the decrease in monomeric flavonoids. During TBV aging an increase in the browning index is observed as a consequence of the polycondensation reactions of flavonoids and of brown melanoidins accumulation.

PRACTICAL APPLICATIONS

Traditional balsamic vinegar is a potentially healthy seasoning with high antioxidant capacity that increases during the aging resulting in a product with a strong antioxidant capacity and rich in phenolic compounds such as phenolic acids, monomeric catechins, flavonols and tannins. It also contains other antioxidants such as melanoidins derived from the Maillard and caramelization reaction that occur during must boiling and traditional balsamic vinegar aging. Independently of their bioavailability, traditional balsamic vinegar can contribute to supply antioxidant molecules that play an important role in protecting the gastrointestinal tract itself against peroxidation, thereby limiting the formation of detrimental lipid degradation products.     

新疆传统发酵酸驼乳中乳酸菌的分离和鉴定

利用MRS琼脂培养基对新疆传统发酵酸驼乳中的乳酸菌进行分离,分别挑取可疑菌落进行革兰氏染色,对镜检结果为革兰氏阳性菌,且细菌形状为球状和杆状的两种菌种进行糖发酵实验与生物化学鉴定.结论是:在两种不同pH值的MRS琼脂培养基上,菌落为灰白色、有透明圈,分别呈球状和杆状的两种菌种为乳球菌和乳杆菌.     

沙棘油主要理化指标的分析检测

按照国家标准方法对购置的沙棘油的主要理化指标及感官指标进行全面分析检测:折光指标(n20)1.471;密度d20200.915 6,d4200.914 0;水分及挥发物0.64%;酸价(AV)15.77 mgKOH/g;碘价(Ⅵ)1922.皂化价(Is)1923 mgKOH/g;过氧化值(PV)12.3 meg/kg.     

CHANGES IN Pb, Cd, Fe, Cu AND Zn LEVELS DURING THE PRODUCTION OF KAŞAR CHEESE

ABSTRACT

Levels of Pb, Cd, Fe, Cu and Zn in milk, curd, pressed curd, fresh cheese, whey, rennet and scalding water taken from two different Ka?ar cheese plants (A and B) in Ankara, Turkey were investigated. The milk used in plant A contained higher amount of Pb, Fe and Zn than the milk used in plant B. Pb level during processing in both dairy plants showed a significant increase from milk to curd (626.2–912.3 µg/kg for plant A and 265.2–371.8 µg/kg, dry weight, for plant B) (P < 0.01). Similarly, Fe, Cu and Zn contents of the curds in plant A and B showed an important increase with respect to the milk (P < 0.01). During transition of the curd to pressed curd and of pressed curd to fresh cheese, almost all metals tested showed a decrease because of the loss of these metals into whey and scalding water. The results showed that curdling the milk was the most important contamination step.

PRACTICAL APPLICATIONS

Heavy metals may enter the human body through food, water, air or absorption through the skin, and can cause metabolic anormalies. Heavy metals may reach our foods from a number of sources. The more important of these are: soil; the chemicals applied to agricultural land; the water used in food processing or cooking; and the equipment, containers and utensils used for food processing, storage or cooking. Milk and milk products are the basic components of the human diet, and among milk products cheese holds an important place. Ka?ar cheese ranks second with respect to consumption, significantly contributing to the Turkish diet. In order to prevent the health risk of consuming contaminated cheeses, it is very important to determine the effect of equipment and process variation on the heavy‐metal content of Ka?ar cheese. The results of this study would help the regulatory authorities to establish a Hazard Analysis and Critical Control Points (HACCP) plan and to identify important contamination sources for Ka?ar and similar kind of cheeses.

     

DYNAMIC CHANGES IN THE COMPOSITION AND PHYSICAL BEHAVIOUR OF DISPENSED BEER FOAM

Beer foam generated under conditions encountered at dispense was separated from beer, allowed to collapse and sampled at regular intervals. The yield of collapsed beer foam decreased logarithmically with time. Analysis of the composition of collapsed beer foam fractions over a period of time, considered to be relevant to actual consumption of beer (30 minutes) showed that polypeptide material and isomerised α acids were selectively partitioned in beer foam. The concentration of total polypeptides, soluble polypeptides, isomerised α acids and foam precipitate material in collapsed beer foam, firstly increased with foam collapse time and then approached maximal values. Under these conditions the concentration of polypeptide material and isomerised α acids increased 10–30 fold and 7 fold respectively as compared to beer. No evidence was obtained for the preferential partition of purine nucleosides and free bases in foam (adenosine + deoxyadenosine, guanosine + deoxyguanosine, adenine, guanine and xanthine).