Mercedes Torre

Effects of dietary fiber and phytic acid on mineral availability

In general, it has been shown that dietary fiber may bind metallic cations in both in vitro and in vivo studies. However, there clearly are many unresolved questions on the effects of high-fiber diets on mineral availability. On one side, the effects of fiber on the utilization of nutrients vary greatly with the amount and type of fiber. In addition, there are many agents in both food and the digestive tract that may affect the mineral binding to fiber: some agents may inhibit binding, while others will enhance it. Also, there are several major difficulties in drawing conclusions from the in vitro and in vivo studies due to the different experimental conditions, methods used to follow the mineral balance, etc. Finally, it must be borne in mind that fiber and phytic acid occur together in fiber-rich diets and, thus, it is difficult to separate the effects of fiber and phytate in the utilization of most essential polyvalent metallic ions. The studies summarized in this review show that the recommendation for increasing dietary fiber in Western communities would not be expected to have any adverse effect on mineral absorption if we increase not only the intake of fiber, but also the dietary intake of other food components such as protein (both vegetable and animal protein) and ascorbic, citric, and oxalic acids (in fruits and vegetables). The adequate intake of minerals, fat, and simple sugars are maintained with this type of diet. The recommendations should be best interpreted in such a way as to prevent the consumption of excessive amounts of phytate, particularly for those whose mineral needs are great. Further studies are still needed in this field in order to understand the conflicting results published in the literature regarding the effects of fiber on the utilization of minerals; however, the studies reviewed in this article may give us an idea of the complexity of mineral availability in fiber-rich, phytate-rich diets.

Composition and characterization of soyabean and related products

Soyabean contains about 48 to 50% proteins. Among these, storage proteins are predominant. 7S and 11S globulins are two storage proteins that constitute 80% of the total protein content in soyabean. Moreover, there are other less abundant storage proteins such as 2S, 9S, and 15S globulins. In addition to globulins, enzymes, protease inhibitors (Kunitz and Bowman-Birk), lectin, and other complete the soya protein content. Different methods exist to characterize soya proteins. These methods involve (1) an isolation of proteins from soya commercial products and (2) the use of analytical techniques for protein determination. Soya proteins may interact with other soya components such as minerals, phytic acid, ascorbic acid, and fiber. These interactions, which depend on soya processing and treatment, can decrease the bioavailability of minerals and proteins. Swelling, solubility, viscosity, and capacity to form a gel, an emulsion, or a foam are the main functional properties of soyabean. They are responsible for the wide use of soya in industrial processes.

Analysis of Soyabean Proteins in Meat Products: A Review

Dr. Lourdes Amigo, Instituto de Fermentaciones, Industriales (CSIC), Juan de la Cierva, 3, 28006 Madrid, Spain The use of soyabean proteins as meat extenders has spread significantly due to the interesting nutritional and functional properties that are present in soyabean proteins. Together with these, health and economical reasons are the major causes for the addition of soyabean proteins to meat products. Nevertheless, despite the good properties associated to soyabean proteins, there are many countries in which the addition of these proteins is forbidden or in which the addition of soyabean proteins is allowed up to a certain extent. Thus, the need of analytical methods enabling the detection of added soyabean proteins in meat products is obvious. Microscopic, electrophoretic, immunologic, and chromatographic methods are the most widely used for this purpose. However, the detection of soyabean proteins in meat products presents difficulties related to the composition (meat species, meat quality, soyabean protein source, presence of other non-meat proteins, etc.) and the processing of the meat products, and, although these analytical methods have tried to overcome all these difficulties, there is still not a method enabling quantitative assessment of soyabean proteins in all kinds of meat products.

Perfusion chromatography: an emergent technique for the analysis of food proteins

Perfusion chromatography is a technique arised to overcome the problem associated with mass transfer in the separation of large molecules such as proteins by high-performance liquid chromatography (HPLC). Perfusion media are constituted by two set of pores: throughpores (6000-8000 A) and diffusive pores (800-1500 A) which enable better access of macromolecules to the inner of the particle by the combination of convective and diffusive flow. As a consequence, times required for a chromatographic separation are reduced. Perfusion media are available in different chromatographic modes: reversed-phase, ion-exchange, hydrophobic interaction, and affinity. From the theoretical models developed to explain the dynamic of retention of solutes in perfusive supports, it was derived that efficiency of a separation was independent of the flow-rate and only depended slightly on the particle diameter. Furthermore, loading capacity was also independent of the superficial velocity. All these advantages have promoted the use of this chromatographic technique for the separation of biomolecules both in analytical and preparative chromatography. Characteristics of perfusion chromatography make this technique very interesting for the analysis of food proteins. Perfusion chromatography enables the assessment of protein composition of a foodstuff at sufficient speed and low cost to be suitable in routine analysis.

The State of the Art of Ligand-Loaded Complexing Resins. Characteristics and Applications

Abstract This review deals with the most recent investigations on the preparation, characterization, and metal sorption properties of ligand-loaded resins obtained by modification of conventional anion-exchange resins and nonionic sorbents with complexing organic reagents. These resins display a selectivity for metal ions that can be applied for the separation and/or preconcentration of metal ions off-line as well as in on-line techniques. In addition, the increasing application in recent years of new functional-modified resins in certain growing scientific areas, namely, electrochemistry, optical-fiber sensors, pharmaceuticals, biochemistry, etc., is discussed. Finally, the immobilization of chelating reagents in types of supports other than conventional resins is also considered.

Chemical characterization of commercial soybean products

Abstract Some commercial soybean products—soybean protein isolate, soybean flour, textured soybean, whole soybeans, and soybean dairy-like products (liquid and powdered milks, shake, yogurt, and infant formulas)—have been analysed for their content in solids, ash, pH, acidity, protein, fat, phosphorus, and some metal ions (calcium, copper, iron, potassium and zinc). The differences found in the protein, phosphorus, and metal ion content and other chemical properties of these products are discussed, taking into account the procedures used to produce the above derivatives.

Perfusion liquid chromatography of whey proteins

A perfusion reversed-phase (RP) HPLC method was developed for the rapid separation of the main bovine whey proteins: alpha-lactalbumin (alpha-LA), serum albumin (BSA) and the genetic variants of beta-lactoglobulin (A and B) (beta-LG A and beta-LG B). For the method development, the influence of factors favouring structural changes of proteins (temperature and organic acid concentration in the mobile phase), gradient and other chromatographic conditions and the mass of protein injected was examined. The optimized method allowed the separation of proteins in about 1.5 min (cycle time 3.5 min) with resolution around 1.0 for the beta-lactoglobulins. The method was applied to the determination of proteins in a whey from raw bovine milk. The precision of the determinations was < or = 3.75 mg per 100 ml (S.D.). With respect to the accuracy, errors < or = 7.0% in the determination of alpha-LA, beta-LG A and beta-LG B were obtained, compared with an RP-HPLC reference method. However, higher errors in the quantification of BSA were found owing to the lack of purity of the peak assigned. In addition, the proposed method has proved to be very useful in the detection of homologous whey proteins from different species (cow, sheep and goat) in milk mixtures.

Interactions of Fe(II), Ca(II) and Fe(III) with high dietary fibre materials: A physicochemical approach

Abstract Interactions of Fe(II), Ca(II), and Fe(III) with five natural food materials, which should be used as fibre sources in the diet, such as pomaces from the production of white wine, cider and olive oil, and lemon peel and pulp, were investigated in vitro. The extent of mineral binding by these concentrates of fibre depended both on the nature and chemical composition of the sample used and on the type of mineral element studied; however, the majority of these samples exhibited a higher capacity to bind Fe(II) than Ca(II) and Fe(III). Two graphic methods have been used to provide basic information on the mineral binding mechanisms for the interactions of these cations with the high-fibre samples: the Scatchard plot, for examining binding by complex formation, and the equation of Langmuir, to predict cation retention by physical adsorption.

Clinical value of p53, c‐erbB‐2, CEA and CA125 regarding relapse, metastasis and death in resectable non‐small cell lung cancer

The prognostic value of p53 and c‐erbB‐2 immunostaining and preoperative serum levels of CEA and CA125 was investigated in a prospective multicentric study including 465 consecutive non‐small cell lung cancer (NSCLC) patients with resectable tumors. Four end‐points were used: lung cancer death, first relapse (either locoregional or metastasis), loco‐regional recurrence and metastasis development. Standard statistical survival methods (Kaplan‐Meier and Cox regression) were used. The specificity of the prognostic effect across different types of tumors was also explored, as had been planned in advance. Our results showed, once again, that pathological T and N classifications continue to be the strongest predictors regarding either relapse or mortality. Three of the studied markers seemed to add further useful information, however, but in a more specific context. For example, increased CEA concentration defined a higher risk population among adenocarcinomas but not among people with squamous tumors; and p53 overexpression implied a worse prognosis mainly in patients with well differentiated tumors. The analysis of type of relapse proved to be very informative. Thus, CA125 level was associated with a worse prognosis mainly related with metastasis development. Another interesting result was the influence of smoking, which showed a clear dose‐response relationship with the probability of metastasis. For future studies, we recommend the inclusion of different endpoints, namely considering the relationship of markers with the type of relapse involved in lung‐cancer recurrence. They can add useful information regarding the complex nature of prognosis.

Rapid separation of soybean globulins by reversed-phase high-performance liquid chromatography

A rapid separation of the main soybean proteins (7S and 11S globulins) was carried out by reversed-phase high-performance liquid chromatography. For this purpose, a linear binary gradient acetonitrile--water--0.1% trifluoroacetic acid, at a flow-rate of 1 ml/min and 50 degrees C temperature was designed. Under the experimental conditions of this work, it was possible to separate five peaks corresponding to the globulins from a soybean protein isolate in 9 min. The characterization of soybean proteins was accomplished by analyzing the 7S and 11S purified fractions obtained from a soybean protein isolate. The method was applied to the separation of soybean proteins from commercial foodstuffs: soybean flour, textured soybean and soybean milks.