Some observations on protein changes in washed myofibrils of bovine muscle

It was found that the protein and water contents of washed myofibrils obtained from bovine longissimus dorsi muscles vary with the rate of pH change during the first hour post mortem. Neither myosin nor actin is responsible for the variation, which is due to changes in the other myofibrillar components. The amount of remaining myofibrillar proteins (RMP), obtained after the sum of myosin and actin is deducted from the total myofibrillar protein (TMP), shows a minimum at a rate of pH change corresponding to a 1-h pH value of 6·7. Apart from this pH-dependent decrease, a further substantial reduction of the RMP fraction was observed, particularly in myofibrils extracted from electrically stimulated muscles. It is considered that the observed changes result from partial proteolysis taking place in muscle during the early hours post mortem. A possible involvement of connectin as a primary substrate for the action of calcium-activated neutral protease is discussed. On the basis of the observed correlation between Warner-Bratzler peak shear force and TMP, a significant influence of pre-rigor muscle status on meat tenderness is suggested.     

Mechanical strength of raw beef from cold-shortened muscles

The resistance to shear of standard samples of raw beef varies in proportion to the degree of extension above rest length or inversely with shortening, an effect opposite to the increase in toughness in cooked meat which follows shortening. An hypothesis which accounts for this effect is tested and discussed in terms of the structure of muscle.     

Some observations on wheat gluten solubilities

A study of wheat protein solubilities in dilute acetic acid is presented. Up to 4% more protein can be extracted from defatted flours than from the non-defatted flour. High-speed homogenisation can render up to 88% of flour protein and up to 97% of dough protein soluble. One criterion for optimum fatty acid or lipid protein interaction (causing protein insolubility) is that the fatty acids or lipids should contain C7-C9 hydrocarbon chain lengths.     

Some observations on the arginine requirement of the growing New Zealand white rabbit

Young meat rabbits of the New Zealand White breed, aged between 5 and 8 weeks, were fed semi-purified diets containing casein as the main protein source, and increasing levels of supplementary arginine to assess their requirements for dietary arginine. On all experimental diets the rabbits achieved good mean growth rates which were not significantly different from the growth rate of 42 g day-¹ on a well-tried control diet. The results are discussed with reference to studies by other workers and the conclusion reached that the requirement for arginine is not greater than 5.6 g kg?¹ diet as fed.     

Some observations on the absorption spectra of various myoglobin derivatives found in meat

The three principal myoglobin states of haem pigment, oxymyoglobin, metmyoglobin reduced myoglobin, and the ferrous nitrous oxide form, nitrosomyoglobin, were prepared as pure pigments in solution. The absorbance spectra of these solutions were determined and extinction coefficients calculated. The position of the absorption peaks showed some small differences compared to published data, in particular the use of absorbance readings at 525 nm as an isobestic point for all three could be questioned. The use of mathematical transforms to first or second difference functions showed merit for the identification of mixtures of some of the myoglobin forms. The second difference function separated the broad absorbance band in the Soret region into two separate troughs, thereby resolving a mixture of oxymyoglobin and reduced myoglobin. It is suggested that based on absorption spectra, similar mathematical transforms could be applied to the interpretation of reflectance spectra of meat and meat products. Further evaluation of such mathematical transformations is required on a range of meat reflectance spectra.     

Proteasome from rabbit skeletal muscle: Some properties and effects on muscle proteins

Rabbit proteasome, likely to be a 20S proteasome, was purified and its properties were investigated to clarify its contribution to proteolysis during meat conditioning. The purified enzyme migrated as a single band on non-denaturing polyacrylamide gel and dissociated to a number of subunits (20000–29000 Da) under denaturing conditions. The molecular mass of this enzyme was found to be 580 000–800 000 Da by Sephacryl S-300 column chromatography. The isoelectric point of this enzyme was 5.5. The optimum pH for hydrolysis of succinyl-Leu-Leu-Val-Tyr-(4-methylcoumaryl-7-amide) (Suc-LLVY-MCA) was 8. This enzyme was almost stable in the range of pH 5–9 and up to 60 °C at pH 7.2. The enzyme activity was inhibited by diisopropyl fluorophosphate (DFP) and chymostatin, but was not affected by EDTA, leupeptin, E-64, bestatin, monoiodoacetic acid or pepstatin. The enzyme was activated about 8-fold by 0.01% sodium dodecyl sulfate (SDS), but was not by ATP or CaCl₂. Remarkably, SDS increased the V_max value of the enzyme. Rabbit proteasome was shown to degrade myosin heavy chain, -actinin, actin, tropomyosin, troponins and myosin light chains in the presence of SDS. In the absence of SDS, no change in myofibrillar proteins was observed. This enzyme did not degrade any sarcoplasmic proteins regardless of the presence of SDS.     

Some observations on the ISO 658 (1980) method for determination of the impurities content in commercial oilseed samples

Data are presented on the chemical analysis of oilseeds and their associated impurities. These data are used to support a discussion of the way different impurities components are currently considered. In particular, it is noted that the oil and free fatty acid contents of shell and fines should be carefully taken into account.     

Some observations on the determination of phenols in smoked fish by solvent extraction: Difficulties and improvements in the methodology

Summary A solvent extraction technique has been used to determine the recovery of a range of wood smoke phenols from fatty fish. It has been shown that the recovery of a number of these phenols is poor when fat is removed by ethyl ether extraction under strongly alkaline conditions. A revised technique has been developed that overcomes this problem and the method has been used in the determination of phenols in cold smoked white and fatty fish.

---

Beobachtungen über die Bestimmung von Phenolen im Räucherfisch durch Liisungsmittel-Extrahierung: Schwierigkeiten und Verbesserung der Methode

Zusammenfassung Zur Wiederfindung von Holzrauch-Phenolen aus Fett-Fisch wurde eine ExtrahierMethode mit Lösungsmitteln angewandt. Es konnte bewiesen werden, daß die Wiederfindungsrate bei einigen dieser Phenole niedrig ist, wenn das Fett durch Ether-Extraktion unter stark alkalischen Bedingungen entfernt wird. Es wurde eine verbesserte Methode entwickelt, die these Schwierigkeit überwindet, so daß sie zur Bestimmung von Phenolen in kaltgeräucher-tem Weiß- und Fett-Fisch angewandt werden konnte.

     

银狐皮毛被及皮板组织构造的研究(续)

用光学显微镜和扫描电镜观察了国产人工饲养银狐的毛被和皮板组织构造 ,测定了毛的长度、细度、密度、毛的鳞片高度和皮板厚度。提供了毛和皮板组织学图片 15幅     

银狐皮毛被及皮板组织构造的研究

用光学显微镜和扫描电镜观察了国产人工饲养银狐的毛被和皮板组织构造 ,测定了毛的长度、细度、密度、毛的鳞片高度和皮板厚度。提供了毛和皮板组织学图片 15幅。     

Some observations on aerobic deterioration in untreated silages and in silages made with formaldehyde-containing additives

Aerobic deterioration of untreated silage and of silage made with formaldehyde-containing additives (FCA) was studied in seven trials in which large stacks were self-fed by cattle. Heating and deterioration on prolonged exposure to air was a problem in some silages made with FCA. It was concluded that the main factors which predisposed these silages to heat were restriction of anaerobic fermentation by the additives, a high pH of 4.7-5.4 and, in three trials, inadequate compaction. In the additive-treated stacks, which showed aerobic deterioration, a zone of elevated temperature developed on the stack top surface. With time this moved to a layer 20-40 cm from the surface, where it remained. The surface layer (0-15 cm) then cooled, its pH rose to 8.5 and a mould flora developed. Both the onset of heating and the rise in pH were related to counts of aerobic bacteria; neither parameter was consistently related to yeast counts. A ten-fold increase in mould counts was associated with each one unit increase in pH. It is suggested that acid-tolerant aerobic bacteria (perhaps assisted by yeasts in some instances) caused the first stage of aerobic deterioration, namely the onset of heating and the rise in pH, and that invasion by moulds then followed as a second stage of the deterioration process. Diminished oxygen tensions in the well compacted lower parts of the stacks appeared responsible for restriction of the heating zone to a depth of 40 cm from the stack top surface.     

Some further observations on the effect of temperature on the fecundity and longevity of Dermestes lardarius L. (Coleoptera: Dermestidae)

The fecundity of Dermestes lardarius L. was determined on a diet of fish-meal, yeast and cholesterol at 65% r.h., 17.5, 20, 22.5, 25, 27.5 and 30°C. Pairs of adults were given a water drink and eggs removed twice weekly. The median life-span of adults was longest at 17.5 and 20°C (maximum of 223 days) and shortest, 56 days, at 30°C. At each temperature, except 30°C, 50% of the females lived longer than males. At temperatures ranging from 17.5 to 27.5°C some females laid much earlier than others and some individuals exhibited two periods of oviposition. The longest oviposition periods were recorded at 20°C and the shortest at 27.5°C. Temperature had a great influence on the numbers of eggs laid. The total yield of eggs reached a peak of 1261 at 20°C and then declined to 52 at 27.5°C. Fifty percent of the females failed to lay at 27°C and no eggs were laid at 30°C. Fecundity of the females was very variable (0–196). The temperature of 20°C seemed to be optimal for egg laying in this species.