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PubMed2006

High pressure-low temperature processing of food proteins.

High pressure-low temperature (HP-LT) processing is of interest in the food field in view of: (i) obtaining a "cold" pasteurisation effect, the level of microbial inactivation being higher after pressurisation at low or sub-zero than at ambient temperature; (ii) limiting the negative impact of atmospheric pressure freezing on food structures. The specific effects of freezing by fast pressure release on the formation of ice I crystals have been investigated on oil in water emulsions stabilized by proteins, and protein gels, showing the formation of a high number of small ice nuclei compared to the long needle-shaped crystals obtained by conventional freezing at 0.1 MPa. It was therefore of interest to study the effects of HP-LT processing on unfolding or dissociation/aggregation phenomena in food proteins, in view of minimizing or controlling structural changes and aggregation reactions, and/or of improving protein functional properties. In the present studies, the effects of HP-LT have been investigated on protein models such as (i) beta-lactoglobulin, i.e., a whey protein with a well known 3-D structure, and (ii) casein micelles, i.e., the main milk protein components, the supramolecular structure of which is not fully elucidated. The effects of HP-LT processing was studied up to 300 MPa at low or sub-zero temperatures and after pressure release, or up to 200 MPa by UV spectroscopy under pressure, allowing to follow reversible structural changes. Pressurisation of approximately 2% beta-lactoglobulin solutions up to 300 MPa at low/subzero temperatures minimizes aggregation reactions, as measured after pressure release. In parallel, such low temperature treatments enhanced the size reduction of casein micelles.

Animals↗

PubMed1987

Nutritional epidemiology: issues and challenges.

Studies of diet in relation to disease raise methodological challenges considerably more complicated than in most epidemiological investigations. Diet is not a single exposure, but rather a complex set of many intercorrelated continuous variables. Moreover, these variables are likely to have non-linear relationships with disease and interact with each other. Many epidemiologists have questioned whether useful measurements of individual diets could be made within populations, due to homogeneity of food intake and imprecision of assessment methods. However, in several recent studies it has been possible to demonstrate reasonable levels of correlation between simple, structured food frequency questionnaires and detailed, weighed assessments of diet. This provides evidence documenting that between-person variation in diet does exist and that simple questionnaires are sufficiently accurate to measure these differences. For a limited set of nutrients, biochemical measurements provide an alternative assessment of exposure. It remains to be seen whether these methodologies can be reliably employed in case-control studies since even small biases due to the presence of illness, which may affect recall of diet or the levels of biochemical parameters, will seriously distort relationships between diet and disease.

Diet↗

PubMed2006

Coexistence of the niche and neutral perspectives in community ecology.

The neutral theory for community structure and biodiversity is dependent on the assumption that species are equivalent to each other in all important ecological respects. We explore what this concept of equivalence means in ecological communities, how such species may arise evolutionarily, and how the possibility of ecological equivalents relates to previous ideas about niche differentiation. We also show that the co-occurrence of ecologically similar or equivalent species is not incompatible with niche theory as has been supposed, because niche relations can sometimes favor coexistence of similar species. We argue that both evolutionary and ecological processes operate to promote the introduction and to sustain the persistence of ecologically similar and in many cases nearly equivalent species embedded in highly structured food webs. Future work should focus on synthesizing niche and neutral perspectives rather than dichotomously debating whether neutral or niche models provide better explanations for community structure and biodiversity.

Biodiversity↗

PubMed1998

Mechanism of compound- and species-specific food effects of structurally related antiarrhythmic drugs, disopyramide and bidisomide.

PURPOSE: To determine mechanism of food effects observed with bidisomide but not with the structurally similar drug, disopyramide. METHODS: Food effect studies of bidisomide and disopyramide were conducted with and without a standardized high fat meal in healthy subjects and in the dog. Intestinal metabolism of disopyramide and absorption of the metabolites were examined after oral administration of the drug to the dogs with portal vein canula implanted. Effects of food or a mixture of amino acids on metabolism of [14C]disopyramide were examined after intraportal infusion of the drug with and without high fat meal and after drug infusion into portal vein with the amino acid mixture, respectively. RESULTS: The systemic availability of bidisomide was markedly reduced with food in humans, whereas the systemic availability of disopyramide did not change notably. In the dog, the systemic availability of bidisomide was also reduced with food. The systemic availability of disopyramide did not change with food. This was due to the fact that reduction in absorption was compensated by reduction of metabolism. There was no evidence for reduction in hepatic and intestinal metabolism with food. CONCLUSIONS: The apparent reduction in disopyramide metabolism with food may be due to an increase in colonal and/or lymphatic absorption. Food effects on the apparent systemic availability of bidisomide and disopyramide in the dog were similar to those in the rat. However, there was substantial species difference in the mechanism of food effects.

Adult↗

PubMed2000

Social-cognitive determinants of nutrition behavior among supermarket food shoppers: a structural equation analysis.

A social-cognitive model of nutrition behavior (A. Bandura, 1997) was tested using structural equation modeling of data from 307 food shoppers recruited from 5 supermarkets in Southwest Virginia. The shoppers were participating in the baseline phase of an ongoing nutrition promotion program. As part of the evaluation, data were collected on the self-efficacy and outcome-expectations components of social-cognitive theory as well as on food purchases and intake. The structural analyses presented here support the social-cognitive model. Self-efficacy, physical outcome expectations, age, socioeconomic status, and number of children were important predictors of nutrition behavior among shoppers. Implications for interventions using social-cognitive variables to improve the nutritional content of food purchases and intake are discussed.

Adult↗

PubMedDate not supplied

Determinants of healthy eating in Canada: an overview and synthesis.

This article uses a population health perspective to examine the complex set of interactions among the determinants of healthy eating. An overview of current knowledge on determinants of healthy eating was organized as follows: 1) individual determinants of personal food choices and 2) collective determinants, including a) environmental determinants as the context for eating behaviours and b) public policies as creating supportive environments for healthy eating. A conceptual synthesis of the literature revealed that individual determinants of personal food choice (physiological state, food preferences, nutritional knowledge, perceptions of healthy eating and psychological factors) are necessary, but not sufficient, to explain eating behaviour, which is highly contextual. Collective determinants of eating behaviour include a wide range of contextual factors, such as the interpersonal environment created by family and peers, the physical environment, which determines food availability and accessibility, the economic environment, in which food is a commodity to be marketed for profit, and the social environment, in which social status (income, education and gender) and cultural milieu are determinants of healthy eating that may be working "invisibly" to structure food choice. Policy is a powerful means of mediating multiple environments. There are gaps in our understanding of the process of intervening in macro-level environments and the impact of such interventions on the promotion of healthy eating. Collective determinants of food choice and policy contexts for promoting healthy eating, therefore, require investment in research. Applying a population health promotion lens to understanding the multiple contexts influencing healthy eating provides insight into prioritizing research and action strategies for the promotion of healthy eating.

Adolescent↗

PubMed2006

Habitat structural complexity mediates food web dynamics in a freshwater macrophyte community.

A considerable amount of research has investigated the influence of habitat structure on predator success, yet few studies have explored the implications for community structure and food-web dynamics. The relative importance of macrophyte structure and fish predation on the composition of the macroinvertebrate and periphyton communities in a lowland river was investigated using a multifactorial caging experiment. We hypothesised that: (1) fish predators are less effective in a more structurally complex macrophyte analogue; (2) strong direct and indirect effects of fish predators (e.g. trophic cascades) are less likely to occur in a structurally complex habitat; and (3) the strength of these patterns is influenced by the composition of the prevailing community assemblage. We measured the abundance and composition of the macroinvertebrate and periphyton communities associated with three different-shaped macrophyte analogues, under different fish predator treatments and at different times. Macrophyte analogue architecture had strong, consistent effects on both the macroinvertebrate and periphyton communities; both were most abundant and diverse on the most structurally complex plant analogue. In contrast, the fish predators affected only a subset of the macroinvertebrate community and there was a suggestion of minor indirect effects on periphyton community composition. Contrary to expectations, the fish predators had their strongest effects in the most structurally complex macrophyte analogue. We conclude that in this system, macrophyte shape strongly regulates the associated freshwater assemblage, resulting in a diverse community structure less likely to exhibit strong effects of fish predation.

Animals↗

PubMed2004

Analysis of a novel class of predictive microbial growth models and application to coculture growth.

In this paper, a novel class of microbial growth models is analysed. In contrast with the currently used logistic type models (e.g., the model of Baranyi and Roberts [Baranyi, J., Roberts, T.A., 1994. A dynamic approach to predicting bacterial growth in food. International Journal of Food Microbiology 23, 277-294]), the novel model class, presented in Van Impe et al. (Van Impe, J.F., Poschet, F., Geeraerd, A.H., Vereecken, K.M., 2004. Towards a novel class of predictive microbial growth models. International Journal of Food Microbiology, this issue), explicitly incorporates nutrient exhaustion and/or metabolic waste product effects inducing stationary phase behaviour. As such, these novel model types can be extended in a natural way towards microbial interactions in cocultures and microbial growth in structured foods. Two illustrative case studies of the novel model types are thoroughly analysed and compared to the widely used model of Baranyi and Roberts. In a first case study, the stationary phase is assumed to be solely resulting from toxic product inhibition and is described as a function of the pH-evolution. In the second case study, substrate exhaustion is the sole cause of the stationary phase. Finally, a more complex case study of a so-called P-model is presented, dealing with a coculture inhibition of Listeria innocua mediated by lactic acid production of Lactococcus lactis.

Coculture Techniques↗

PubMed1999

Validating predictive models of food spoilage organisms.

The accuracy and bias of a predictive model for the maximum specific growth rate of Pseudomonas spp. were studied by means of percentage discrepancy and bias indicators. These were calculated for observations obtained both in laboratory media and in food. When independent pseudomonad data generated in broth were compared with model predictions, the error was smaller than in the case of food. The extent to which the food structure and composition of the microflora contribute to the overall error of the model was quantified.

Animals↗

PubMed2004

Interaction of fat availability and sex on postprandial satiety and cholecystokinin after mixed-food meals.

BACKGROUND: Cholecystokinin (CCK) is associated with fat-induced satiety. OBJECTIVE: The primary objective of the present study was to determine, in an acute meal setting, whether the availability of dietary fat for alimentary processing, and hence the stimulation of CCK, affects the postmeal satiety response in men and women. DESIGN: In a within-subjects design, subjects (8 men, 7 women) consumed 1 of 3 isoenergetic mixed-food test meals 1 wk apart in random order. The test meals contained 30% of energy from fat, of which more than two-thirds was derived from whole almonds, almond oil, or a mix of safflower and corn oils. Visual analogue scales were used to assess indexes of satiety at defined time points up to 6 h after meal consumption. Blood was sampled at corresponding time points for measurement of CCK, glucose, insulin, and triacylglycerol. Subsequent food intake was also assessed. RESULTS: All meals suppressed hunger and induced a pattern of satiety that was sex-specific and corresponded with the CCK response. Women had higher plasma CCK concentrations and experienced greater satiety after the almond oil and control meals (fat as oil) than after the whole almond meal (fat in whole food structure). Men showed no differential response among meals for CCK and satiety. Plasma triacylglycerol differed by time among meals but not by sex, and no significant differences in glucose and insulin were found. CONCLUSIONS: The satiety response to dietary fat provided in oil or whole food form is influenced by sex and is dependent on the availability of fat to stimulate CCK release in women but not in men.

Adult↗

PubMed2001

Gastric proteolysis in preterm infants fed mother's milk or formula.

Gastric proteolysis is assumed to be low in the newborn (Britton & Koldovsky 1989). Postprandial pepsin output is significantly lower in preterm infants than adults, 589 vs. 3352U/kg, respectively (Armand et al. 1995, 1996). We now report on gastric proteolysis in preterm infants (gestation age, 29 weeks; postnatal age, 5-6 weeks) gavage-fed mother's milk or preemie formula. The data show that a) the nonprotein component is higher in human milk than formula, b) net proteolysis amounts to 15% of protein, c) gastric proteolysis is lower than lipolysis and, contrary to the latter, is not enhanced by milk feeding (Armand et al. 1996). We suggest that stomach pH, enzyme output, and food structure are the reasons for differences in gastric digestion of protein and fat in infants.

Aging↗

PubMed2004

Towards a novel class of predictive microbial growth models.

Food safety and quality are influenced by the presence (and possible proliferation) of pathogenic and spoilage microorganisms during the life cycle of the product (i.e., from the raw ingredients at the start of the production process until the moment of consumption). In order to simulate and predict microbial evolution in foods, mathematical models are developed in the field of predictive microbiology. In general, microbial growth is a self-limiting process, principally due to either (i) the exhaustion of one of the essential nutrients, and/or (ii) the accumulation of toxic products that inhibit growth. Nowadays, most mathematical models used in predictive microbiology do not explicitly incorporate this basic microbial knowledge. In this paper, a novel class of microbial growth models is proposed. In contrast with the currently used logistic type models, e.g., the model of Baranyi and Roberts [Baranyi, J., Roberts, T.A., 1994. A dynamic approach to predicting bacterial growth in food. International Journal of Food Microbiology 23, 277-294], the novel model class explicitly incorporates nutrient exhaustion and/or metabolic waste product effects. As such, this novel model prototype constitutes an elementary building block to be extended in a natural way towards, e.g., microbial interactions in co-cultures (mediated by metabolic products) and microbial growth in structured foods (influenced by, e.g., local substrate concentrations). While under certain conditions the mathematical equivalence with classical logistic type models is clear and results in equal fitting capacities and parameter estimation quality (see Poschet et al. [Poschet, F., Vereecken, K.M., Geeraerd, A.H., Nicolai, B.M., Van Impe, J.F., 2004. Analysis of a novel class of predictive microbial growth models and application to co-culture growth. International Journal of Food Microbiology, this issue] for a more elaborated analysis in this respect), the biological interpretability and extendability represent the main added value.

Bacteria↗

PubMed2001

Protein glycation, diabetes, and aging.

Biological amines react with reducing sugars to form a complex family of rearranged and dehydrated covalent adducts that are often yellow-brown and/or fluorescent and include many cross-linked structures. Food chemists have long studied this process as a source of flavor, color, and texture changes in cooked, processed, and stored foods. During the 1970s and 1980s, it was realized that this process, called the Maillard reaction or advanced glycation, also occurs slowly in vivo. Advanced glycation endproducts (AGEs) that form are implicated, causing the complications of diabetes and aging, primarily via adventitious and crosslinking of proteins. Long-lived proteins such as structural collagen and lens crystallins particularly are implicated as pathogenic targets of AGE processes. AGE formation in vascular wall collagen appears to be an especially deleterious event, causing crosslinking of collagen molecules to each other and to circulating proteins. This leads to plaque formation, basement membrane thickening, and loss of vascular elasticity. The chemistry of these later-stage, glycation-derived crosslinks is still incompletely understood but, based on the hypothesis that AGE formation involves reactive carbonyl groups, the authors introduced the carbonyl reagent aminoguanidine hydrochloride as an inhibitor of AGE formation in vivo in the mid 1980s. Subsequent studies by many researchers have shown the effectiveness of aminoguanidine in slowing or preventing a wide range of complications of diabetes and aging in animals and, recently, in humans. Since, the authors have developed a new class of agents, exemplified by 4,5-dimethyl-3-phenacylthiazolium chloride (DPTC), which can chemically break already-formed AGE protein-protein crosslinks. These agents are based on a new theory of AGE crosslinking that postulates that alpha-dicarbonyl structures are present in AGE protein-protein crosslinks. In studies in aged animals, DPTC has been shown to be capable of reverting indices of vascular compliance to levels seen in younger animals. Human clinical trials are underway.

Aging↗

PubMed2006

A Rudimentary labellar speculum in Cymbidium lowianum (Rchb.f.) Rchb.f. and Cymbidium devonianum Paxton (Orchidaceae).

BACKGROUND AND AIMS: The labellar 'hairs' of some Cymbidium spp. are said to be thin-walled and to contain 'plasma', oil and sugars and it has long been speculated that they may function as food-hairs. However, the present authors' preliminary studies showed that certain atypical papillae may have a different role and, by reflecting light, function as a speculum. The purpose of the paper is to test this hypothesis. METHODS: Light microscopy, scanning electron microscopy, transmission electron microscopy, histochemistry and ultraviolet photography were used to investigate the structure, food content and light-reflecting properties of these papillae. KEY RESULTS AND CONCLUSIONS: The labellum of Cymbidium lowianum (Rchb.f.) Rchb.f. is densely clothed with obconical to conical papillae with wide bases and pointed tips. However, on either side of the median axis of the lip occur silvery patches comprising papillae with truncated tips and it is thought that these reflect light and thereby attract insect pollinators. Similar patches are also found in Cymbidium devonianum Paxton, and in both species, they are set against a reddish background, which, since bees cannot perceive this colour, probably appears dark to the insect thus enhancing the visual impact of the light-reflecting patches. In Cymbidium tigrinum Parish ex Hook. and Cymbidium mastersii Griff. ex Lindl., however, the labellum is mainly white and no light-reflecting patches were observed. Instead, unlike C. lowianum and C. devonianum, these species are highly fragrant and the attraction of insects probably depends to a greater extent on olfactory cues. In C. lowianum both types of papillae contain protein, starch and lipid bodies but only protein is seemingly present at elevated concentrations. However, lipoidal material also occurs upon the surface of the labellum and it is possible that this may be gathered by insects as reported for C. iridifolium A. Cunn (syn. C. madidum Lindl.). The labellar papillae of C. lowianum, thus, have the potential to function as food-hairs, although direct evidence for this is lacking.

Animals↗

PubMed2002

Dietary intake analysis in institutionalized elderly: a focus on nutrient density.

BACKGROUND: Inadequate food intake in old age can lead to marginal or suboptimal nutrient intakes causing the deterioration of physiological and health states. OBJECTIVE: To describe, by intake assessment, nutritional status of institutionalized elderly and to compare the data to other studies findings. DESIGN: Dietary intake was assessed in 50 (18 males, 32 females, average age 84 6 years) institutionalized elderly according to data collected by using structured food frequency questionnaires based on the institutional kitchen recipes, weekly menu and portion size. RESULTS: Daily energy intake was 1.91 0.48 Mcal and energy density was 4.97 kcal/g dry matter. Energy derived from protein and fat was 15.1% and 35.4%, respectively. Dietary fiber consumption was very low, 3.92 g/Mcal. Calcium intake of all of the subjects, and magnesium, zinc and copper intakes of most of them, were low. Iron intake of almost all of the subjects was sufficient or above RDA. Intake of vitamins D, E, B6, thiamin (vitamin B1) and folic acid in all or most of the subjects was low. In almost all of the 39 studies and reviews, including ours, densities of at least two nutrients did not meet the calculated RDA density. Particularly low were the nutrient densities of vitamins C and E, thiamin, vitamin B6, folic acid and vitamin D, as well as of calcium, magnesium, zinc and copper. CONCLUSION: Supplementation with half the RDA of micronutrients (except for vitamin A and iron) may result in micronutrient intakes that are higher than two-thirds of the RDA.

Aged↗

PubMed2003

Glycemic index of local foods and diets: the Mediterranean experience.

The Mediterranean diet is a healthful eating pattern associated with the prevention of coronary heart disease (CHD). Its main features are moderate intake of total fat (predominantly monounsaturated fat), low consumption of saturated fat and cholesterol-rich foods, and high intake of starch. Although this type of diet has beneficial effects on lipid metabolism, its high carbohydrate content might not be ideal for patients with diabetes or other conditions associated with insulin resistance (e.g., metabolic syndrome), who are known to be at particular risk of CHD. We therefore evaluated the glycemic response to starchy foods based on wheat (typical of the Italian diet) in patients with type 2 diabetes and identified certain characteristics of foods explaining their effects on postprandial glucose response. We found that spaghetti and potato dumplings, because of their low blood glucose response, represent a valid alternative to other starchy foods typical of the Mediterranean diet. Food structure plays an important role in determining the accessibility of starch to digestion, thus influencing the postprandial blood glucose response, which modulates plasma insulin and lipid levels.

Blood Glucose↗

PubMed1991

The effect of mechanical deformation on the movement of water in foods.

This study has shown the importance of relating NMR spectroscopic information on the water in model food structures to the mechanical properties of those structures. Analysis of the NMR relaxation data can be used to examine the distribution of water domain sizes, and this has been related to the mechanical properties of the samples. A novel NMR probe-head has been designed, which allows both the NMR and the mechanical data to be simultaneously measured during compression of the sample. This probe-head allows compressive stress/strain data to be obtained directly from the NMR sample, allowing changes in the distribution of the water to be directly correlated to changes in mechanical properties.

Chemical Phenomena↗

PubMed2000

Effects of benzo(a)pyrene and size of organic matter particles on bioaccumulation and growth of Asellus aquaticus.

The effects of sediment-bound toxicants to aquatic invertebrates may vary due to differences in bioavailability, food quality, or food structure. The equilibrium partitioning theory (EPT) assumes that organic matter content of sediments and not structure of organic matter is relevant for biological effects of polycyclic aromatic hydrocarbons. To test this hypothesis effects of benzo(a)pyrene (B(a)P) and size of sediment organic matter particles on the bioaccumulation and growth of the waterlouse Asellus aquaticus were studied in laboratory microcosms. Sediments and A. aquaticus were both sampled in an unpolluted, spring-fed pond. The sampled sediment was divided into two portions. From one portion the size of the organic matter particles was mechanically reduced. One set of each sediment fraction (fine and coarse) was spiked with B(a)P and incubated for 3 weeks resulting in a concentration of 70 mg B(a)P per kg sediment. Bioassays of 32 days were performed in a 2 x 2 factorial design with four replicas of each treatment. The results showed that the growth of A. aquaticus was mainly influenced by the size of organic matter particles. Growth was significantly less (27%) on finer sediments than on coarser sediments. The increase in length was 9-14% lower in the spiked sediments, but this difference was not significant. The reduced growth of A. aquaticus on finer sediments may be due to a change in the availability and/or quality of food together with a change in feeding behavior. The coarse and fine spiked sediment types did not differ significantly with respect to the sediment water partition coefficient, the organic carbon water partition coefficient, and the bioconcentration factor. In contrast, the biota to sediment accumulation factors were significantly 15% higher in the cosms with coarse sediments than in cosms with fine sediments. However, this difference is too small to conflict with EPT.

Animals↗