Joyce I. Boye

Effects of physicochemical factors on the secondary structure of β-lactoglobulin

Fourier transform infrared spectroscopy and differential scanning calorimetry were used as complementary techniques to study changes in the secondary structure of beta-lactoglobulin under various physicochemical conditions. The effects of pH (3-9), NaCl (0-2 M), and lactose, glucose and sucrose (100-500 g/l) in the temperature range 25-100 degrees C on the conformation sensitive amide I band in the i.r. spectrum of beta-lactoglobulin in D2O solution were examined. The 1692 cm-1 band in the amide I band profile had not been definitively assigned in previous studies of the i.r. spectrum of beta-lactoglobulin. The decrease in this band at ambient temperature with time or upon mild heating was attributed to slow H-D exchange, indicating that it was due to a structure buried deep within the protein. The disappearance of the 1692 cm-1 band on heating was accompanied by the appearance of two bands at 1684 and 1629 cm-1, assigned to beta-sheets. The 1692 cm-1 band was therefore attributed to a beta-type structure. beta-Lactoglobulin showed maximum thermal stability at pH 3 and was easily denatured at pH 9. On denaturation, the protein unfolded into more extensive random coil structures at pH 9 than at pH 3. After 10 h at pH 9 (25 degrees C), beta-lactoglobulin was partly denatured. Heating to 60-80 degrees C generally resulted in the loss of secondary structure. At all pH values studied, two new bands at 1618 and 1684 cm-1, characteristic of intermolecular beta-sheet structure and associated with aggregation, were observed after the initial denaturation. Differential scanning calorimetry studies indicated that the thermal stability of beta-lactoglobulin was enhanced in the presence of sugars. The Fourier transform i.r. results obtained provide evidence that sugars promoted the unfolding of beta-lactoglobulin via multiple transition pathways leading to a transition state resisting aggregation.

Thermal denaturation of mixtures of α-lactalbumin and β-lactoglobulin: a differential scanning calorimetric study

Abstract The thermal denaturation of α-lactalbumin (α-lac), β-lactoglobulin (β-lg) and a mixture of the two proteins in the presence of several sugars, sodium salts and at various pH values was studied by differential scanning calorimetry. The effects of N -ethylmaleimide (NEM), cysteine, urea and sodium dodecyl sulfate (SDS) were also investigated. The temperature of denaturation ( T d ) of β-lg decreased from 71.9°C in the absence of α-lac to 69.1°C in its presence. In contrast, an increase of 2.5°C was observed in the T d of apo-α-lac when heated in the presence of β-lg suggesting that α-lac was made more thermally stable in the presence of β-lg. Glucose and galactose had the greatest effect in stabilizing the proteins against thermal denaturation with the effect being greater for β-lg than for α-lac. A decrease in thermal stability of both proteins was observed in the presence of sodium bicarbonate; sodium ascorbate, however, had a stabilizing effect. Renaturation of α-lac was prevented in the presence of cysteine and NEM, but not in urea or SDS. Translucent gels were formed when the α-lac/β-lg mixtures were heated in the presence of all five sugars and in the presence of cysteine, urea and SDS but not in NEM. This suggests that disulfide–sulfhydryl interchange reactions may be primarily responsible for the gelation of α-lac/β-lg mixtures.

Allergenicity of Soybean: New Developments in Identification of Allergenic Proteins, Cross-Reactivities and Hypoallergenization Technologies

Soybean is considered one of the “big eight” foods that are believed to be responsible for 90% of all allergenic reactions. Soy allergy is of particular importance, because soybeans are widely used in processed foods and, therefore, represent a particularly insidious source of hidden allergens. Although significant advances have been made in the identification and characterization of soybean allergens, scientists are not completely certain about which proteins in soy cause allergic reactions. At least 16 allergens have been identified. Most of them, as with other plant food allergens, have a metabolic, storage, or protective function. These allergens belong to protein families which have conserved structural features in relation with their biological activity, which explains the wide immunochemical cross-recognition observed among members of the legume family. Detailed analysis of the structure-allergenicity relationships has been hampered by the complexity and heterogeneity of soybean proteins. A variety of technological approaches have been attempted to decrease soybean allergenicity. This paper provides a comprehensive review of the current body of knowledge on the identification and characterization of soybean allergens, as well as an update on current hypoallergenization techniques.

Food allergies in developing and emerging economies: need for comprehensive data on prevalence rates

Although much is known today about the prevalence of food allergy in the developed world, there are serious knowledge gaps about the prevalence rates of food allergy in developing countries. Food allergy affects up to 6% of children and 4% of adults. Symptoms include urticaria, gastrointestinal distress, failure to thrive, anaphylaxis and even death. There are over 170 foods known to provoke allergic reactions. Of these, the most common foods responsible for inducing 90% of reported allergic reactions are peanuts, milk, eggs, wheat, nuts (e.g., hazelnuts, walnuts, almonds, cashews, pecans, etc.), soybeans, fish, crustaceans and shellfish. Current assumptions are that prevalence rates are lower in developing countries and emerging economies such as China, Brazil and India which raises questions about potential health impacts should the assumptions not be supported by evidence. As the health and social burden of food allergy can be significant, national and international efforts focusing on food security, food safety, food quality and dietary diversity need to pay special attention to the role of food allergy in order to avoid marginalization of sub-populations in the community. More importantly, as the major food sources used in international food aid programs are frequently priority allergens (e.g., peanut, milk, eggs, soybean, fish, wheat), and due to the similarities between food allergy and some malnutrition symptoms, it will be increasingly important to understand and assess the interplay between food allergy and nutrition in order to protect and identify appropriate sources of foods for sensitized sub-populations especially in economically disadvantaged countries and communities.

Achievements and Challenges in Improving the Nutritional Quality of Food Legumes

Quality aspects of food crops have globally important market economic and health repercussions in the current climate of food security. Grain legumes have high potential for the nutritional quality improvement of foods, but limited data on manipulating seed quality is available as the primary focus has been hitherto on phenotypic and agronomic trait improvement. This has resulted in a lack of innovation and low attractiveness of legume food products that, with the emergence of novel food habits, have together contributed to reduced legume food consumption. This trend now needs to be challenged and circumvented. In this review we have assessed the key factors affecting the nutritional quality of legume seeds such as protein, starch, dietary fiber, natural antioxidant compounds and anti-nutritional factors. All have been reviewed with emphasis on how these components might influence consumer acceptance and functional properties of legume based food products. Biofortification approaches and technological processing are discussed as ways in which the nutritional value of legumes and their consumption might be enhanced. In order to increase consumption of grain legumes, we propose that efforts should concentrate on identifying nutritionally enhanced and genetically diverse germplasm, and on linking genetics with sensorial and processing quality. This will assist the development of breeding/selection tools for traits that determine consumer demand, facilitating the implementation of quality breeding objectives in legume breeding programs. Equally important, efforts should focus on developing attractive, convenient ready-to-eat and tasty legume-based food formulations, contributing to the diversification of healthier and more nutritional diets. As a result of such a targeted effort, legume cultivation and consumption could be enhanced leading to a reduction in both the global economic burden caused by malnutrition and associated chronic diseases, and the environmental impact of agriculture.

Fast: Towards safe and effective subcutaneous immunotherapy of persistent life-threatening food allergies

The FAST project (Food Allergy Specific Immunotherapy) aims at the development of safe and effective treatment of food allergies, targeting prevalent, persistent and severe allergy to fish and peach. Classical allergen-specific immunotherapy (SIT), using subcutaneous injections with aqueous food extracts may be effective but has proven to be accompanied by too many anaphylactic side-effects. FAST aims to develop a safe alternative by replacing food extracts with hypoallergenic recombinant major allergens as the active ingredients of SIT. Both severe fish and peach allergy are caused by a single major allergen, parvalbumin (Cyp c 1) and lipid transfer protein (Pru p 3), respectively. Two approaches are being evaluated for achieving hypoallergenicity, i.e. site-directed mutagenesis and chemical modification. The most promising hypoallergens will be produced under GMP conditions. After pre-clinical testing (toxicology testing and efficacy in mouse models), SCIT with alum-absorbed hypoallergens will be evaluated in phase I/IIa and IIb randomized double-blind placebo-controlled (DBPC) clinical trials, with the DBPC food challenge as primary read-out. To understand the underlying immune mechanisms in depth serological and cellular immune analyses will be performed, allowing identification of novel biomarkers for monitoring treatment efficacy. FAST aims at improving the quality of life of food allergic patients by providing a safe and effective treatment that will significantly lower their threshold for fish or peach intake, thereby decreasing their anxiety and dependence on rescue medication.

Simultaneous detection of multi-allergens in an incurred food matrix using ELISA, multiplex flow cytometry and liquid chromatography mass spectrometry (LC-MS).

Food allergy is a public health concern and an important food safety issue. Food allergies affect up to 6% of infants and children and 4% of adults. The objective of this work was to determine differences in the detection of single and multiple allergens (i.e., casein, soy protein, and gluten) in an incurred food matrix before and after baking. Cookies were used as a model food system. Three methods, namely, multiplex assay (a new optimized method based on flow cytometry for multiple allergen analysis), enzyme-linked immunosorbent assay (ELISA) using commercial kits and LC-MS were used to detect allergens in the samples before and after baking. The ELISA kits performed well in detecting allergens in the raw samples with recoveries of 91-108%, 88-127% and 85-108% for casein, soy protein and gluten, respectively. Recoveries were poor for the baked cookies (67-90%, 66-95% and 66-88% for casein, soy protein and gluten, respectively). The multiplex flow cytometry assay permitted multiple allergen detection in the raw samples, with the following recoveries based on soluble protein: casein, 95-107%; soy protein, 92-97%, and gluten, 96-99%. Data for the baked cookies were as follows: casein, 84-90%; soy protein, 80-88%, and gluten, 80-90%. The LC-MS technique detected marker peptides that could be used to identify allergens in the baked food samples up to concentrations of 10 ppm for casein and soy protein, and 100 ppm for gluten. To the best of our knowledge, the current study is the first to compare ELISA, LC-MS and multiplex flow cytometry methods for the detection of multiple allergens simultaneously incurred in a model food system.

Advances in the Design and Production of Reduced-Fat and Reduced-Cholesterol Salad Dressing and Mayonnaise: A Review

Reducing fat and cholesterol content is currently one of the primary trends in food product innovation. Fat plays an important role in maintaining food quality, particularly the texture, flavor, and stability of food emulsion products. The food industry faces major challenges in seeking to produce reduced-fat and low-cholesterol mayonnaise and dressings that have attributes similar to full-fat products. Efficient monitoring of products to ensure desirable quality requires knowledge of their physicochemical characteristics, including appearance, rheology, emulsion stability, microstructure, and flavor, as well as particle size and charge distribution. The purpose of this paper is to provide a comprehensive overview of trends in the development of reduced-fat and low-cholesterol dressings. The effects of reducing fat content or using various fat replacers on the physicochemical properties of dressing and mayonnaise products are detailed with supporting experimental results. The possibility of using plant-based ingredients or reduced-cholesterol egg yolk in the formulation of such products is also examined.

Effect of processing on post-bottling haze formation in apple juice

Abstract Post-bottling haze formation in clarified apple juice produced under a variety of processing conditions was studied. Turbidity of the juice was monitored at intervals during a 6-month storage period. Changing the pasteurization temperature of raw juice and omitting the addition of amyloglucosidase did not retard or prevent haze development. Omission of the fining procedure, however, resulted in an increase in turbidity of 1.36 NTU and visual observation of larger quantities of haze. Fining with a gelatin/bentonite ratio of 1:1 gave the least haze. Thermocoagulation treatment applied to the juice prior to ultrafiltration also did not retard or prevent haze formation. Ultrafiltration at lower processing temperatures resulted in the development of less haze. At higher temperatures an increase in turbidity of over 14 NTU was observed. The results suggest that optimization of the fining procedure and ultrafiltration could be used to retard post-bottling haze in apple juice.

Current Trends in Green Technologies in Food Production and Processing

Finding a balance between food supply and demand in a manner that is sustainable and which ensures the long-term survival of the human species will be one of the most important challenges for humankind in the coming decades. Global population growth in the last several centuries with the attendant demands resulting from industrialization has made the need for food production and processing an important issue. This need is expected to increase in the next half century when the population of the world exceeds 9 billion. Environmental concerns related to food production and processing which require consideration include land use change and tremendous reduction in biodiversity, aquatic eutrophication by nitrogenous and phosphorus substances caused by over-fertilization, climate change, water shortages due to irrigation, ecotoxicity, and human effects of pesticides, among others. This review summarizes key highlights from the recently published book entitled Green Technologies in Food Production and Processing which provides a comprehensive summary of the current status of the agriculture and agri-food sectors in regard to environmental sustainability and material and energy stewardship and further provides strategies that can be used by industries to enhance the use of environmentally friendly technologies for food production and processing.