Lech Ozimek

Digestibility of amino acids in swine: Results and their practical applications. A review

Abstract Many studies have been carried out on the topic of amino acid digestibility in swine during the last two decades. The ileal analysis method should be the method of choice for determining amino acid digestibilities. This method is very sensitive for detecting differences in amino acid digestibilities, as these result from processing conditions or from inherent differences between samples of the same feedstuff. Amino acid digestibility values from the literature, determined with the ileal analysis method, are summarized and show large differences in amino acid digestibilities between feedstuffs and among different samples of the same feedstuff. At present it seems most appropriate to relate to amino acid digestibilities in terms of their apparent values. Studies in which the 15 N isotope dilution technique was used to determine the endogenous amino acid losses have shown that the traditional methods for determining the endogenous amino acid losses should be re-evaluated. Recent studies have clearly shown improvements in diet formulation practices, especially when a good quality protein supplement is replaced by protein supplement(s) of lower quality combined with supplementary amino acids, and when diets are formulated on the basis of digestible rather than total supply of the limiting amino acid(s). In addition, in order to present improved values for amino acid requirements, these should be expressed as digestible rather than as total.

Purification of glycomacropeptide from dialyzed and non-dialyzed sweet whey by anion-exchange chromatography at different pH values

Glycomacropeptide (GMP) was purified from sweet whey dialyzed in water by anion-exchange chromatography on DEAE-Sephacel at pH 2.0–4.5. The optimum pH range was 2.5–4.0. The yield of purified GMP increased and its sialic acid concentration decreased with increasing pH value. The GMP had an apparent isoelectric point < 3.8. Dialysis of sweet whey was shown to be important to maximize the yield of GMP adsorbed to the anion-exchanger. Only highly sialylated GMP, accounting for approximately 55% of total sialic acid content, was adsorbed on the anion-exchanger from non-dialyzed sweet whey.

Purification of κ‐Casien Glycomacropeptide from Sweet Whey with Undetectable Level of Phenylalanine

Glycomacropeptide (GMP) found in sweet whey is a biologically active compound released from κ‐casein by the action of chymosin during cheese making. This study was undertaken to purify GMP from sweet whey as a research chemical on a laboratory scale. Glycomacropeptide was isolated from proteins and other non‐GMP compounds by deproteinization with trichloroacetic acid and gel chromatography on Sephacryl S‐200. The purified GMP accounted for 0.12% of dry sweet whey powder and contained 107.0, 50.9, 61.2 and 4.3 μg, respectively, of sialic acid, galactose, galactosamine and phosphorus per mg dry weight. The GMP was of high purity, with its amino acid composition showing undetectable levels of phenylalanine, tyrosine and arginine, the amino acids that do not occur in bovine GMP. On gel electrophoresis, the GMP showed a single broad band with an average mobility faster than that of carbonic anhydrase (molecular weight = 31 kDa). The purified GMP may be used as a standard glycopeptide in chromatography and electrophoresis and may also be used to test various known or unknown properties and biological activities of this compound.

Purification of glycomacropeptide from non-dialyzable fraction of sweet whey by anion-exchange chromatography

Glycomacropeptide (GMP) was purified from non-dialyzable fraction of sweet whey by anion-exchange chromatography on DEAE-Sephacel at two pHs 6.4 and 3.0. Chromatography at pH 3.0 (but not pH 6.4) gave a GMP fraction of high purity with its yield (1 g from every litre of whey) being approximately 100 times higher than that shown in the previous report. It was concluded that DEAE-Sephacel chromatography at pH 3.0 is a simple useful method to separate GMP from most whey proteins. It may be applicable to a large scale production of GMP.

Purification of glycomacropeptide from non-dialyzable fraction of sweet whey by hydrophobic interaction chromatography on phenyl-agarose

Non-dialyzable fraction of sweet whey was chromatographed on a column of phenyl-agarose equilibrated with 0.01 M sodium phosphate buffer, pH 6.8 containing 5 M NaCl. Most whey proteins were adsorbed on the column, while the glycomacropeptide (GMP) was not. Amino acid analysis of the GMP fraction showed presence of traces (each < 1 residue/peptide) of arginine, histidine and phenylalanine which are not found in GMP. The estimated yield of GMP fraction was approximately 1.6 g l−1 of sweet whey.

Detection of keratan sulfate by immunological methods in commercial chondroitin sulfate preparations

Chondroitin sulfate (CS), a well known nutraceutical, and keratan sulfate (KS) are glycosaminoglycans involved in the structure of cartilage proteoglycan, aggrecan. Since CS is extracted from cartilage, there may be a possibility that purified CS is contaminated with small amount of KS. A total of 15 samples, including four samples of CS as laboratory reagents, one sample of CS as a food additive and ten samples of dietary supplements containing CS were examined to detect KS in these samples by using immunodiffusion and enzyme-linked immunosorbent assay (ELISA) with anti-KS monoclonal antibody (IgM). With the exception of three samples of CS as laboratory reagents, all samples were found to contain varying amounts of KS. It was concluded that both the immunodiffusion, a quick one-step method, and ELISA for quantification, are reliable methods to detect KS contamination in CS products.

Synergistic enhancement in the co-gelation of salt-soluble pea proteins and whey proteins

This paper investigated the enhancement of thermal gelation properties when salt-soluble pea proteins were co-gelated with whey proteins in NaCl solutions, using different blend ratios, total protein concentrations, pH, and salt concentrations. Results showed that the thermal co-gelation of pea/whey proteins blended in ratio of 2:8 in NaCl solutions showed synergistic enhancement in storage modulus, gel hardness, paste viscosity and minimum gelation concentrations. The highest synergistic enhancement was observed at pH 6.0 as compared with pH 4.0 and 8.0, and at the lower total protein concentration of 10% as compared with 16% and 22% (w/v), as well as in lower NaCl concentrations of 0.5% and 1.0% as compared with 1.5%, 2.0%, 2.5%, and 3.0% (w/v). The least gelation concentrations were also lower in the different pea/whey protein blend ratios than in pure pea or whey proteins, when dissolved in 1.0% or 2.5% (w/v) NaCl aqueous solutions.

Chemical composition of the infrapatellar fat pad of swine

The porcine infrapatellar fat pad is a structure composed of adipocytes and adipose connective tissues. Limited information is available concerning its chemical composition. Samples of the fat pad collected from young hogs were dissected into two portions: a relatively hard core of the pad with cushioning properties (inner tissue), and a soft adipose tissue surrounding the core (outer tissue). The inner tissue contained less moisture and nitrogen than did the outer tissue. The yield of dry‐delipidated tissue was also lower in the inner tissue, indicating a higher content of lipid in this tissue. Fatty acid analysis showed that the proportions of C18: 1, C16: 1 and C18: 2n‐6 are higher, and the proportion of C16: 0 is lower in the inner than in the outer tissue. Collagen is the major protein, with relatively small amounts of glycosaminoglycans in both tissues. The content of hyaluronic acid relative to sulphated galactosaminoglycan was lower in the inner than in the outer tissue. The electrophoresis pattern of sulphated galactosaminoglycan was also different between the two tissues. These results suggest that chemical composition varies between adipose tissues with different biomechanical function.

Immunological detection of keratan sulfate in meat products with and without mechanically separated chicken meat

Keratan sulfate is a glycosaminoglycan found in the structure of cartilage proteoglycans, aggrecan and fibromodulin. This study was undertaken to detect this glycosaminoglycan in meat products containing mechanically separated chicken meat (MSCM) having cartilage particles. Dry-defatted samples of MSCM and meat products with or without MSCM were digested with papain, and a non-dialyzable fraction from each papain digest was examined by immunodiffusion analysis using anti-keratan sulfate monoclonal antibody (IgM). No precipitine line was formed with the antibody for all samples of meat products without MSCM, while a sample of MSCM and all samples of meat products with MSCM gave clear precipitine lines with the antibody. The immunodiffusion test described here appears to be a simple sensitive specific method for qualitative analysis of keratan sulfate, which in combination with other methods may be useful for detection of MSCM in meat products.

Prevention of Cardiovascular Disease and Diabetes Mellitus In Low and Middle Income Countries

Hyperglycemia as a component of metabolic syndrome, appears to be an important risk marker of vascular disease in most developing countries which are under transition from poverty to affluence. Despite a moderate increase in fat intake and low rates of obesity, the risk of coronary artery disease (CAD) and diabetes is rapidly increasing in most of the developing economies. It is a paradox that in some of these countries the increased risk of people to diabetes and CAD, especially at a younger age, is difficult to explain by conventional risk factors. It is possible that the presence of new risk factors especially higher lipoprotein (a)(Lpa), hyperhomocysteinemia, insulin resistance, low high density lipoprotein cholesterol and poor nutrition during fetal life, infancy and childhood may explain at least in part, the cause of this paradox. The prevalence of obesity, central obesity, smoking, physical inactivity and stress are rapidly increasing in low and middle income populations, due to economic development. In high income populations, there is a decrease in tobacco consumption, increase in physical activity and dietary restrictions, due to learning of the message of prevention, resulting into reduction in coronary and sroke mortality. Hypertension, (5-10%) diabetes(3-5%) and CAD(3-4%) are very low in the adult, rural populations of India, China, and in the African sub-continent which has less economic development. However, in urban and immigrant populations of India and China, the prevalence of hypertension (>140/90, 25-30%), diabetes (6-18%) and CAD (7-14%) are significantly higher than they are in some of the high income populations. Mean serum cholesterol (180-200 mg/dl), obesity (5-8%) and dietary fat intake (25-30% en/day) are para- doxically not very high and do not explain the cause of increased susceptibility to CAD and diabetes in some South Asian countries. The force of lipid- related risk factors and refined starches and sugar appears to be greater in these populations due to the presence of the above factors and results into CVD and diabetes at a younger age in these countries. These find- ings may require modification of the existing American and European guidelines, proposed for prevention of CAD, in high income populations. Wild foods or designer foods (400-500g/day) substitution (www.columbus-concept.com) for proatherogenic foods; in conjunction with moderate physical activity and cessation of tobacco, may be protective against deaths and disability due to CVD and diabetes in most of these countries.