Water-holding Capacity Measurements Research Articles

Interactions of polysaccharide stabilisers with casein aggregates in stirred skim-milk yoghurt

Abstract The stabilisation mechanisms of low-methoxy pectin, λ -carrageenan, guar gum, locust bean gum and xanthan in stirred yoghurt were investigated using dynamic oscillatory rheometry and water holding capacity measurements. As the level of low-methoxy pectin and λ -carrageenan increased, the stabilisation mechanism was consistent with the model of casein aggregates passing through a region of bridging flocculation, followed by partial steric stabilisation. For guar gum, locust bean gum and xanthan, the results were consistent with depletion flocculation at a low concentration of stabiliser, and trapped aggregated casein within a viscous polysaccharide solution at higher concentrations. A peak was observed for the phase angle of guar-stabilised yoghurt as a function of frequency, from 4.5 to 0.2 Hz as guar increased from 0.5 to 5 g L−1 for 1-day yoghurt, and from 4.5 to 2.2 Hz as the yoghurt containing 0.5 g L−1 guar gum was aged from 1 to 42 days. Results are interpreted with an understanding that the rheological behaviour is affected by the pre-sharing conditions of the stirred yogurt.

Gelation of mixed systems whey protein concentrate–gluten in acidic conditions

Gels of whey protein concentrate (WPC)–gluten were prepared by heating WPC–gluten dispersions (10% whey protein/0–5–10% gluten protein, w/w; pH 3.75 or 4.2). Gels were characterized through solubility assays in different extraction solutions, measures of water-holding capacity (WHC), firmness, elasticity and relaxation time, and light microscopy. Differential scanning calorimetry (DSC) of WPC–gluten dispersions was also performed. Gluten increases the firmness and elasticity of gels, mainly at pH 4.2. The WHC also increases with gluten content, being higher at pH 3.75 than at pH 4.2. Solubility assays indicate that electrostatic forces, hydrophobic and H bindings would be involved in maintaining the gel structure of WPC gels at pH 3.75 and 4.2, whereas in mixed gels of WPC–gluten, the principal forces responsible for the maintenance of the gel structure at these pHs would be hydrophobic and H bindings, and in gels prepared at pH 4.2 also disulfide bonds, but in a minor extent. The presence of gluten shifts the apparent transition temperature for whey protein denaturation towards lower temperatures. Gels with gluten present a smooth network with gaps and a more elastic appearance, as observed by light microscopy.

Comparison of Dietary Fibre from By-products of Processing Fruits and Greens and from Cereals

The dietary fibre constituents of apple, pear, orange, peach, artichoke and asparagus dietary fibre concentrates and of wheat and oat bran were measured using an enzymatic-gravimetric method. In addition, the water-holding capacity of the dietary fibre concentrates and cereals was estimated by centrifugation.Dietary fibre concentrates of fruits and greens showed a high content of total dietary fibre (35–59 g/100 g), insoluble dietary fibre (21–44 g/100 g) and soluble dietary fibre (10–14 g/100 g), referred to dry matter. The soluble fraction was found to be greater dietary fibre concentrates of fruits and greens than in wheat and oat bran (3–4 g/100 g). Measurements of water-holding capacity showed that dietary fibre concentrates of fruits and greens had a greater affinity for water than those from cereals.

Gelation of whey protein concentrate-cassava starch in acidic conditions.

Whey protein concentrate (WPC)-cassava starch (CS) gels were prepared by heating WPC-CS dispersions (0-12.5% protein-0-4.2% starch, w/w; pH 3.75 and 4.2). Gels were characterized by measures of water-holding capacity (WHC), estimation of the relative size and/or density distribution of the gel particles, and light microscopy. Differential scanning calorimetry (DSC) of WPC-CS dispersions was also performed. Results show that CS increased the WHC of gels. Mixed gels presented separate zones of gelatinized starch and aggregated protein and a higher proportion of large/high-density particles. DSC assays showed that starch gelatinization preceded protein denaturation during heating. Starch gelatinization shifted to higher temperatures in dispersions containing WPC, due to the presence of whey proteins, lactose, and calcium.

Reference methods supported by OECD and their use in Mediterranean meat products

With the highly appreciated support by the Organisation for Economic Co-operation and Development (OECD) since 1993, three groups of experts met in the spring of the years 1993 to 1995 in Kulmbach, Germany to agree on recommendations of reference methods for the most important physical characteristics of meat. Three methods each for the measurements of water-holding capacity and meat texture (tenderness) and one for meat colour determination were written down and published at the 39th to the 41st International Congresses of Meat Science and Technology (1993–1995). As for the standardized method of chemical compounds, e.g. protein or fat in meat published by AOAC, ISO, etc., an international acceptance of these physical OECD methods is expected. This paper encompasses all the methods for the first time and gives in this way the opportunity to use them as a tool for quality assurance in meat plants and for comparison between plants. It opens up for meat and meat products, in this case in Mediterranean countries, the possibility to evaluate their products, by common methods.

Rapid method for determining water-holding capacity in meat using video image analysis and simple formulae

To accelerate measurement of the water-holding capacity (WHC) of meat by the press method, video image analysis (VIA) and formulae were investigated. The areas of meat and meat liquid on filter paper were little affected by changes in the operating conditions of the VIA system. VIA is associated with greater repeatability, less variation due to operators and was less time consuming than planimetry. When VIA was applied to a variety of fresh meats (beef, pork, chicken and duck meat), it was possible to measure the areas of meat and liquid on filter paper under a translucent plastic plate, immediately after pressing, without drawing an outline of the meat area. VIA was also able to measure cooked meat. Drying on filter paper decreased the areas of meat and liquid slightly but hardly changed the meat/liquid area ratio. The meat/liquid area ratio was correlated ( P < 0.01, r = 0.92) with the WHC measurements obtained by conventional formulae including sample moisture. VIA combined with mmeat/liquid ratio is a rapid stable and efficient technique for measuring WHC by the press method.

Measuring water-holding capacity in pork musculature with a tensiometer

The water-holding capacity (WHC) of post-mortem porcine musculature is an important quality trait, and it is desirable for the industry to assess its variations ,for purposes of evaluating and processing pork products. There are several procedures to accurately determine WHC, but most are either too slow, too expensive or are impractical for commercial application. Since WHC is also important when examining the characteristics of soil, scientists routinely use an instrument called a tensiometer for this measurement. Therefore, we explored the potential application of this technique for assessing WHC in post-rigor pork muscle. The cost, potential speed and invasive application of the tensiometer in muscle were attractive characteristics. A sample (29) of pork loins, representing considerable variation in WHC were used to test the applicability of a commercial tensiometer. When tensiometer measurements were compared to 48 h drip loss, the results indicated the tensiometer could accurately detect the variations in free fluids expressed in muscle and that the procedure could be applied quickly and invasively without altering the commercial value of the product. However, particles (primarily protein and fat) in the muscle fluid became imbedded in the pores of the tensiometer ceramic tip, thus impairing the repeated use of the instrument. A plastic filter was developed to prevent clogging, but it could not be molded adequately to permit rapid insertion and removal for on-line measurements of WHC. Therefore, despite the various desirable features of the tensiometer, it failed to meet some requirements considered essential for further testing as a potential commercial, on-line procedure. First, the clogging problem must be resolved The study also indicated that the filter paper test would be more appropriate than the tensiometer for use in field tests to predict WHC when limited numbers of samples were to be tested.

Dietary fibre: The use of in‐vitro and rat models to predict action on stool output in man

AbstractAn in‐vitro model (fermentation and water holding capacity measurement) and a rat model were compared for their ability to predict the action of dietary fibre on stool output in man. A range of different purified or semipurified fibres were studied: wheat bran, pectin, carboxymethylcellulose, xanthan, guar, karaya, tragacanth and gellan. Using equations derived from previous studies, prediction indices from in‐vitro studies were compared with the effects of these fibres on stool output in rat and man. The rat model was better as a predictor for stool output (r = 0.94, P &lt; 0.005) in man but the log in‐vitro predictive index was significantly correlated with stool output in both rat (r = 0.87, P &lt; 0.02) and man (r = 0.84, P &lt; 0.04).Since in‐vitro methods are less expensive and time consuming than animal studies, the log in‐vitro predictive index may provide a useful pre‐screening device for new dietary fibre sources or detecting changes in the action of dietary fibres during the manufacturing process.

A note on the relationships between measures of water holding capacity in the M. longissimus dorsi and total drip loss from butchered pig carcasses during storage

Twenty pig carcasses were selected to represent a range of meat quality. The water holding capacity (WHC) of the M. longissimus dorsi (LD) was estimated using several methods and the usefulness of these measures examined to predict the overall loss in weight from the butchered carcasses when jointed and displayed in a manner corresponding to a retail situation. There was a linear relationship between the logarithms of percentage loss in weight of the butchered carcass and days of display time. The total weight loss from the butchered carcasses after 5 days ranged from 2·2 to 6·4% and the best relationship with this weight loss was for WHC assessed by loss of exudate from slices of LD suspended in netting bags for 72 h at 1°C (r = 0·88, P < 0·001). Measures of WHC based on high or low speed centrifugation, or a filter paper press method, gave slightly poorer correlations. However, all WHC methods except low speed centrifugations gave correlations which were better than those with pH measured at 45 min post mortem, or reflectance or Fibre Optic Probe Values at 24 h post mortem.

THE EFFECT OF pH, POLYPHOSPHATES AND DIFFERENT SALTS ON WATER RETENTION PROPERTIES OF GROUND TROUT MUSCLE

The water binding potential (WBP) and expressible moisture (EM) curves of ground rainbow trout white muscle versus pH are different, particularly in the region from pH 5.0 to 7.0. The effect of different salts such as CaCl2, Mg Cl2, NaCl, Nal and Na2SO4 on WBP suggests that for the same salts, cations cause a smaller change than anions. On the other hand, the EM measurements suggest that cations have a greater effect on this measurement than anions. In the case of WBP, the effect of tripolyphosphate and pyrophosphate can be attributed solely to their effect on pH. These results indicate the differences between the two methods and suggest that they measure different components of the water retention properties of a complex system, and thus water holding capacity measurements must be interpreted with care.

Effect of cooking and preservation methods on the Water Holding Capacity (WHC) of mullet fish in relation with changes occurred in muscle proteins

The WHC of mullet fish (Mugil cephalus) had been studied in relation to changes occurring in muscle proteins by different methods of traditional cooking, such as cooking in boiling water for 20 min and deep frying. Also, the WHC of mullet fish was determined as a result of curing and frozen storage at −15 °C for 1, 2, and 3 months. It has been found that the WHC measurements were closely related to changes occurred in muscle proteins, especially the sarcoplasmic and myofibrillar types. The myofibrillar proteins were found to be more labile for such changes than the sarcoplasmic ones, which ensured their important role in determining the WHC of mullet fish meat and correspondingly its tenderness.

A method to measure the water-holding properties of dietary fibre using suction pressure.

1. Water-holding capacity (WHC) of dietary fibre is usually considered as the amount of water held but the manner in which water is held by the fibre matrix may be more relevant in understanding the role of fibre in nutrition. 2. A method used to determine WHC under physiological conditions has been adapted to determine how strongly water is held by fibre. Solutions of compounds, such as polyethylene glycol, of known osmotic potential are used to generate a suction pressure across a dialysis membrane containing a fibre sample. The WHC at each suction pressure can then be determined. 3. The method can be applied to water-soluble and water-insoluble sources of fibre. Fibre sources studied included potato fibre concentrate, bran and gum arabic. 4. Results are comparable to other similar systems of WHC measurement for gels and suggest that vegetable fibre has water-holding properties more akin to a true gel than bran. Bran has very poor water-holding properties. 5. Differences in WHC between fibre sources are more apparent if WHC is considered as fibre concentration (g fibre/g water). 6. Differences in the water-holding properties could be important in determining fibre activity in the gut.

An examination of factors which may affect the water holding capacity of dietary fibre.

1. Dietary fibre has a water holding capacity (WHC) and this is a function of the fibre source and method of measurement. Water can be associated with fibre either as trapped water or bound water. This makes it difficult to predict the ability of fibre to influence stool weight in humans. 2. Examination of various fibre concentrates for chemical composition, as neutral detergent fibre (NDF), acid detergent fiber (ADF) and lignin; structure, by scanning electron microscopy; WHC, by centrifugation, suggests that WHC is more a function of fibre structure than chemical composition. Cereal fibre and vegetable fibre have a different chemical composition and are structurally very distinct. Structure is also dependent on the method of fibre preparation. 3. Measurement of WHC by centrifugation gives an estimate of the water which can be bound and also trapped by the fibre. The amount of trapped water will depend on the structure of the fibre whereas bound water will depend on the chemical composition.

Exertional myopathy in Finnish Landrace pigs a survey of the situation and evaluation of different control methods

The exertional myopathy situation is surveyed for the top of the breeding pyramid of the Finnish Landrace breed by testing 2,003 pigs and from material on the Norwegian Landrace (86 pigs). The usefulness of the different methods as well as practical measures with regard to the breeding programme are discussed. The halothane sensitivity frequency in the Finnish Landrace breed was found to be 12.4%, indicating that about 58 % of all Finnish Landrace pigs at the top of breeding pyramid have the halothane sensitivity gene (Haln). In contrast, a frequency of only 3.2 % was found in the Norwegian material. Of the Finnish Landrace pigs 60.7 % had the H blood group factor a, 38.0 % factor c and 16.7 %none of these factors. In the Norwegian material 62.0 % had factor a and 55.6 % factor c. Of the Finnish hal+ pigs 91.1% had the H blood group factor a and 3.2 % factor c, while 6.1 % had none of these factors. About 96.6 % of the hal+ pigs had the Phi enzyme type BB and 3.4% the Phi-type AB. None of the Phi-type AA pigs were sensitive to halothane. Phi AA was found to be rare in the Finnish Landrace, with only 1.5 % of the animals having this Phi type. The water-holding capacity measurements from muscle biopsies taken from the pigs at the end of the halothane test did not show statistically significant differences between groups of hal+ and hal— pigs. It was concluded from the results of the present study that the measurement of CK serum activity in nonstressed pigs is not very useful for identification of the hetcrozygotic carriers of the Haln gene.The iterativeness of the CK test in non-stressed pigs was found tobe poor, but muscle tissue might have infected some of the serum samples taken from the vena cava and so caused false high serum CK activity. The halothane test is reliable for the identification of Haln gene homozygotes when conducted on pigs older than 50 days. The Phi AA type is so rare that Phi enzyme typing in Finland is of limited value at present for the breeding programme. A determination of the H blood group factors a and c of all pigs intended for breeding is advised. By increasing the number of pigs with the H blood group factor c it should be possible to reduce the exertional myopathy problem in the Finnish Landrace breed. Preferential use of the desirable genotype c of the H blood group system should be more attractive to breeders than selecting against the undesirable H blood group factor a, especially as many of the H a/a and H a/ pigs have a high K index and a high percentage of lean meat on the carcase. The best a/a and a/pigs may be kept as breeding animals but have to be mated only to H c/ pigs. Because some H c/ pigs are carriers of the Haln gene and a high K index and percentage of lean meat on the carcase favour carriers of the Haln gene, it is most probable that the existing low frequency of H c/ pigs sensitive to halothane will change in the future in an unfavourable direction. It is therefore advisable to stipulate a halothane test based on a progeny test for all H c/ boars with a high K index. Halothane-sensitive sows would be especially suitable for these test matings.

ミオシン区蛋白質ゲルの保水性-I

Water holding capacity (WHC) of myosin-fraction (“M”) gel was determined under varied pH conditions by centrifugal method (8, 000rpm, 20 min.). 1. WHC of “M” gel is greater than that of muscle homogenate, being maximum in isoelectric zone in contrast with the latter which is minimum in this region. 2. WHC of isoelectric “M” gel decreases if pH is shifted to ?? 4.5 or ?? 8. Similarly decreases WHC of “M” gel formed in the alkaline side on readjustment of pH to ?? 4.5. 3. If pH of “M” gel formed in acid or alkaline side is brought to isoelectric zone, WHC is not only less than that of isoelectric gel, but also of the original gel. 4. If pH of isoelectric or alkaline gel is brought to ?? 4.5, WHC of the reformed gel is smaller than that of gel formed at pH ?? 4.5. Results 1 and 2 might be interpreted by an assumption that firmness of structure sufficient to hold water against pressure applied in measurement of WHC has a decisive influence on WHC in the case of gels with relatively weak structure as “M” gel. In Result 3 WHC decreases, though the structure of reformed gel is supposed to be thickened by pH adjustment. This might be probably due to that syneresis has more pronounced effect than firmness of structure. Result 4 can not be explained either by loosening of structure nor syneresis.