Jonathan C. Allen

Growth rates of a human colon adenocarcinoma cell line are regulated by the milk protein alpha-lactalbumin.

The whey protein alpha-lactalbumin, derived from human milk, has been shown to inhibit proliferation of mammary epithelial cells and rat kidney cells. We have shown that bovine alpha-lactalbumin also has antiproliferative effects in human colon adenocarcinoma cell lines. During a 5-day dose-dependent growth study, bovine alpha-lactalbumin was added to Caco-2 or HT-29 monolayers in amounts from 5 to 35 microg/mL. Low concentrations of alpha-lactalbumin (10-25 microg/mL) stimulated growth during the first 3 to 4 days. After growing for 4 days, proliferation ceased and viable cell numbers decreased dramatically in the alpha-lactalbumin-treated cultures, suggesting a delayed initiation of apoptosis. This experiment demonstrates the acute bioactive effects of small concentrations of alpha-lactalbumin, compared with the high concentrations of other proteins in the media. These results suggest that alpha-lactalbumin in milk may promote health by inhibiting growth of potential cancer cells. Further studies will identify the role of calcium in the bioactivity of alpha-lactalbumin.

Effects of High-Pressure Processing on Immunoglobulin A and Lysozyme Activity in Human Milk

Banked human milk, processed using low-temperature/long-time or Holder pasteurization, inactivates pathogenic microorganisms but degrades important biochemical components. High-pressure processing kinetics favor inactivation of microorganisms with retention of biochemical activity and nutritional quality of foods. The effects of high-pressure processing (400 MPa) and low-temperature/long-time pasteurization (62.5°C, 30 minutes) on total immunoglobulin A and lysozyme activity in human milk were investigated. Indirect modified enzyme-linked immunosorbent and a Micrococcus lysodeikticus turbidimetric assay were performed to measure immunoglobulin A immunoactivity and lysozyme activity, respectively. Pressure-treated samples retained significantly higher (P < .05) levels of immunoglobulin A and lysozyme activity compared to samples treated with low-temperature/ long-time pasteurization. These data suggest that high-pressure processing is a potential alternative to thermal pasteurization of human milk that can give greater retention of some bioactive components. Further research is needed to determine whether high-pressure processing can inactivate pathogens of concern in donor human milk. J Hum Lact. 23(3):253-261.

Utilization of Dairy Byproduct Proteins, Surfactants, and Enzymes in Frozen Dough

Use of natural additives is gaining popularity among the masses as they are becoming more conscious about their diet and health. Frozen dough products are one of the recent examples of value-added cereal products which face stability problems during extended storage periods of times. Dairy whey proteins, surfactants, and certain enzymes are considered important natural additives which could be used to control the water redistribution problem in the dough structure during the storage condition. They interact with the starch and gluten network in a dough system and thus behave as dough improvers and strengtheners. These natural additives not only help to bind extra moisture but also to improve texture and sensory attributes in frozen dough bakery products.

The Nutritive and Immunoprotective Quality of Human Milk beyond 1 Year Postpartum Are Lactation-Duration-Based Donor Exclusions Justified?

Donor human milk is critical for the fragile preterm infant who does not have access to his or her mother’s milk, improving survival rates and quality of survival and decreasing hospital stay. Despite the opening of donor milk banks around the world, shortages continue as demand for donor milk exceeds supply. One potential means of increasing supply is by reducing exclusion criteria that prohibit mothers from donating milk based on duration of lactation. Minimal research has been done on the composition of human milk during the second year of lactation, with most research focusing on the nutritive compounds and not the immunoprotective compounds. Several immunoprotective compounds, including lysozyme, lactoferrin, secretory immunoglobulin A, and oligosaccharides, are abundant in human milk compared to bovine-based infant formula and are partially or fully retained during Holder pasteurization, making them an important differentiating feature of donor milk. A PubMed search was conducted to review studies in human milk composition during the second year of lactation. Limitations of existing research include sample collection protocols, small study sizes, and use of populations that may have been at risk for nutritional deficiencies. Stable concentrations of several components were reported including protein, lactose, iron, copper, lactoferrin, and secretory immunoglobulin A. Lysozyme concentration increased during extended lactation, while zinc and calcium concentrations declined into the second year. Conflicting findings were reported on fat content, and no information was available regarding oligosaccharide content. More research is needed to create evidence-based guidelines regarding the nutritive and immunoprotective value of donor milk throughout the course of lactation.

Fatty Acids, Diet, and Body Indices of Type II Diabetic American Whites and Blacks and Ghanaians

OBJECTIVE This research was designed to study the diet, lipid profile, and metabolic and body indices of type II diabetic and non-diabetic subjects among American white and black and Ghanaian populations. METHODS Fifty-one type II diabetic and non-diabetic volunteers were recruited through medical clinics. Data collected included food intake and anthropometric measurement. Blood samples were taken for glucose and serum lipid analyses. Serum non-esterified fatty acids, very low-density lipoproteins, low-density lipoproteins, high-density lipoproteins, total cholesterol, and triacylglycerols levels were measured. RESULTS The Ghanaian subjects had lower body mass indexes than did the American white and black subjects (P < 0.01), although they recorded the highest carbohydrate intake. Dietary fat intake was not significantly correlated with body fat level or body mass index among the different observational groups. The serum ratio of saturated to polyunsaturated fat was higher in all diabetics than in controls and higher in Ghanaians than in Americans. Total cholesterol, triacylglycerols, and lipoproteins were within normal ranges for diabetic and non-diabetic subjects. The ratio of total cholesterol to high-density lipoprotein cholesterol was slightly elevated among the white diabetics (P < 0.05). CONCLUSIONS The data showed a higher metabolism of carbohydrate for energy in the Ghanaian group than in the other groups. In addition, fat metabolism may differ between Americans and Ghanaians. For many variables, black Americans were more similar to white Americans than to Ghanaians. These observations imply that cultural factors may contribute more than ethnic origin to the etiology of diabetes.

Chemical Optimization of Protein Extraction from Sweet Potato (Ipomoea batatas) Peel

UNLABELLED Proteins isolated from sweet potatoes (Ipomoea batatas) have been shown to possess antidiabetic, antioxidant, and antiproliferative properties. The objective of this study was to chemically optimize a process for extracting proteins from sweet potato peel. The extraction procedure involved mixing peel with saline solvent to dissolve proteins and then precipitating with CaCl(2). Quadratic and segmented models were used to determine the optimum NaCl concentration and peel to solvent ratio to maximize protein solubility while minimizing solvent usage. A segmented model was also used to optimize the concentration of CaCl(2) used for precipitation. The highest yield was obtained by mixing blanched peelings with 59.7 mL of 0.025 mM NaCl per g peel and then precipitating with 6.8 mM CaCl(2). The results of this study show that potentially valuable proteins can be extracted from peel generated during processing of sweet potatoes and industrial costs can be minimized by using these optimum conditions. PRACTICAL APPLICATION Potentially valuable proteins can be extracted from sweet potato peel, a waste product of sweet potato processing.

A longitudinal study of human milk composition in the second year postpartum: implications for human milk banking.

While the composition of human milk has been studied extensively in the first year of lactation, there is a paucity of data regarding human milk composition beyond one year postpartum. Policies vary at milk banks around the world regarding how long lactating women are eligible to donate their milk. The primary purpose of this study is to describe longitudinal changes in human milk composition in the second year postpartum to support the development of evidence based guidelines regarding how long lactating women can donate human milk to a milk bank. Nineteen lactating women in North Carolina provided monthly milk samples from 11 months to 17 months postpartum (N = 131), and two non-profit milk banks provided (N = 33) pooled, unpasteurized milk samples from 51 approved donors less than one year postpartum. There was a significant increase (P < 0.05) in the concentration of total protein, lactoferrin, lysozyme, Immunoglobulin A, oligosaccharides and sodium in longitudinal samples of mothers milk between 11 and 17 months postpartum, while zinc and calcium concentrations declined, and no changes were observed in lactose, fat, iron and potassium. Human milk in the second year postpartum contained significantly higher concentrations of total protein, lactoferrin, lysozyme and Immunoglobulin A, than milk bank samples, and significantly lower concentrations of zinc, calcium, iron and oligosaccharides. Accepting milk bank donations beyond one year postpartum is a potential strategy for increasing the supply of donor milk, but may require mineral fortification.

Human Milk Antibacterial Factors

Bovine milk will eventually spoil at refrigeration temperatures, but endogenous or exogenous pathogenic or spoilage bacteria in human milk stored for delayed feeding will die. We investigated the mechanism for these antibacterial properties and their response to high-tempertature, short-time (HTST, 72°C-75°C, 15 sec) and low-temperature long-time (LTLT, 65°C, 30min) pasteurization. NonpathogenicListeria innocua(106cfu/mL) was inoculated into raw and processed bovine and human milk; bacterial plate counts twice weekly determined antibacterial activities. Up to 99% ofL. innocuawere killed and further growth was inhibited in raw and pasteurized human milk for at least 60 days at 4°C. Reactive IgA antibodies againstListeriaantigens were demonstrated by enzyme immunoassay in some human milk samples; sIgA activity againstEscherichia coliO antigens was significantly decreased by heat treatments (raw, 1.8; HTST, 1.1; LTLT, 1.3 activity units). Adding human lactoferrin (0.5-20 mg/mL) to theListeriainoculum (-107cfu/mL) in 1% peptone water did not inhibit bacterial growth.

Susceptibility of sweet potato (Ipomoea batatas) peel proteins to digestive enzymes

Sweet potato proteins have been shown to possess antioxidant and antidiabetic properties in vivo. The ability of a protein to exhibit systemic effects is somewhat unusual as proteins are typically susceptible to digestive enzymes. This study was undertaken to better understand how digestive enzymes affect sweet potato proteins. Two fractions of industrially processed sweet potato peel, containing 6.8% and 8.5% protein and 80.5% and 83.3% carbohydrate, were used as a source of protein. Sweet potato proteins were incubated with pepsin, trypsin, and chymotrypsin and protein breakdown was visualized with SDS-PAGE. After pepsin digestion, samples were assayed for amylase inhibitory activity. Sporamin, the major storage protein in sweet potatoes, which functions as a trypsin inhibitor as well, exhibited resistance to pepsin, trypsin, and chymotrypsin. Sporamin from blanched peel of orange sweet potatoes was less resistant to pepsin digestion than sporamin from outer peel and from extract of the white-skinned Caiapo sweet potato. Trypsin inhibitory activity remained after simulated gastric digestion, with the Caiapo potato protein and peel samples exhibiting higher inhibitory activity compared to the blanched peel sample. Amylase and chymotrypsin inhibitory activity was not present in any of the samples after digestion.

Free zinc concentration in bovine milk measured by analytical affinity chromatography with immobilized metallothionein.

A new analytical affinity chromatography method was developed for measuring the free [Zn2+] concentration in bovine milk. The column was generated by immobilizing avidin and attaching biotinylated metallothionein (MT) on controlled-pore glass beads. Zinc bound to the MT column at physiological free [Zn2+] concentration and was dissociated again in an elution buffer of pH 2. The distributions of extrinsically added65Zn and native zinc in different fractions of milk were virtually identical, validating the use of extrinsic labeling in studies of the free [Zn2+] concentration in milk. Extrinsically labeled whey fractions were mixed with standard solutions whose free [Zn2+] concentrations were calculated by computer model.65Zn retained by the column provided an indication of free [Zn2+] concentration in the mixture, and by interpolation, in the original milk. The free [Zn2+] concentration measured by the affinity chromatography method in the milk of a group of six cows was 90.4±29.7 pM. This value is similar to estimates of free [Zn2+] concentrations in other biological fluids by entirely different methods. Measurement of free [Zn2+] may be helpful in understanding the physiology and biochemistry of zinc metabolism.