Microstructure, rheological and water mobility behaviour of plant-based protein isolates (pea and quinoa) and locust bean gum mixtures.

This work reports the impact of locust bean gum (LBG) in the continuous phase of plant-based proteins, i.e. quinoa protein (QPI) and pea protein isolates (PPI). Experimental measurements such as confocal microscopy, rheological analysis and water mobility via nuclear magnetic resonance (nmr) spin-spin relaxation time (T2) were carried out. The influence of LBG on the rheological properties of QPI and PPI is consistent with an exchange-based nmr interpretation of T2 for biopolymer and water. Addition of LBG increased the viscoelastic properties (storage and loss modulus) and shear viscosities of the mixtures. LBG interacted with both plant proteins, resulting in the formation of more dense protein networks and protein coacervates. A stronger interaction between the PPI and LBG was observed, resulting in higher shear viscosities with lower water mobility as compared to QPI:LBG formulations. Results indicated that the interaction between the protein and polysaccharide played a significant role in the microstructure, its rheological properties and consequently water mobility.

Ethnicity impact on oral processing behaviour and glycemic response to noodles: Chinese (Asian) vs. New Zealander (Caucasian).

There is an increasing awareness of the link between food breakdown during chewing and its nutrient release and absorption in the gastrointestinal tract. However, how oral processing behaviour varies among different ethnic groups, and how such difference further impacts on bolus characteristics and consequently glycemic response (GR) are not well understood. In this study, we recruited a group of Asian (Chinese) subjects in China (n = 32) and a group of Caucasian subjects in New Zealand (n = 30), both aged between 18 and 30 years, and compared their blood glucose level (BGL) over 120 min following consumption of a glucose drink and cooked white noodles. We also assessed their chewing behaviour, unstimulated saliva flow rate, and ready-to-swallow bolus characteristics to determine whether these measures explain the ethnic differences in postprandial glycaemia. Compared to New Zealand subjects, the Chinese subjects showed 35% slower saliva flow rate but around 2 times higher salivary α-amylase activity in the unstimulated state. During consumption of noodles, Chinese subjects on average took a larger mouthful size, chewed each mouthful for longer and swallowed a larger number of particles with a smaller particle size area. Total GR measured by area under the curve (IAUC) was higher among the Chinese subjects. They also experienced higher BGL at 15 min, as well as higher peak BGL. There were strong correlations observed between oral processing and GR parameters. Results of this study confirmed the significance of oral processing in determining food digestion, and will provide new insights on the role of ethnicity in influencing people's physiological response to food.

Chewing differences in consumers affect the digestion and colonic fermentation outcomes: in vitro studies.

It is important to understand variability in consumer chewing behavior for designing food products that deliver desired functionalities for target consumer segments. In this study, we selected 29 participants, representing the large range of chewing variation we had observed in 142 healthy young adults, and investigated the influence of chewing behavior on gastrointestinal digestion and colonic fermentation, using in vitro models and brown rice as a model food. Chewing behavior measured by video observations and chewing outcome differed widely between participants, resulting in large differences in the digestibility of carbohydrates. Inter-individual differences in chewing behavior and chewing outcome also significantly affected in vitro patterns of microbial composition and the production of organic acid metabolites, resulting from colonic fermentation, which is increasingly recognized to be important for human health. These digestion/fermentation outcomes were largely related with the chewing time per mouthful, proportion of bolus particles bigger than 2 mm and amount of saliva added to the bolus during chewing. No significant relationships were found with other chewing trajectory and oral physiological measures. These results suggest that modification of chewing may be an effective strategy to control blood glucose levels and to shape gut microbiota and their metabolites, without altering diets, and that further in vivo studies are warranted to confirm these in vitro findings.

Diet quality indices and postmenopausal breast cancer survival.

Research on diet in breast cancer survival has been focused on single nutrients or foods, particularly dietary fat, fruits, vegetables, fiber, and alcohol. We hypothesized that diet quality indices decrease the risk of total and non-breast-cancer-related deaths in women diagnosed with breast cancer. We evaluated 4 dietary quality scores: Alternate Healthy Eating Index (AHEI), Diet Quality Index-Revised (DQIR), Recommended Food Score (RFS), and the alternate Mediterranean Diet Score (aMED), among 2,729 women from the Nurses' Health Study with invasive Stage 1-3 breast cancer diagnosed between 1978 and 1998 with follow-up through 2004. In multivariate adjusted analyses, no association was found between diet quality indices and either total or non-breast-cancer-related deaths. However, a higher aMED score was associated with a lower risk of non-breast-cancer death in women with low physical activity; the RR comparing the highest to lowest tertile was 0.39 (95% CI, 0.20-0.75, P trend = 0.0004). Our results suggest that a higher-quality diet after breast cancer diagnosis does not considerably change the risk of death from breast cancer. However, healthy dietary choices may be important because women are at risk of death from non-breast-cancer-related causes affected by diet.

Bread breakdown pathways during mastication: impact of wheat bran fortification.

The aim of this study was to investigate the impact of wheat bran fortification on the mastication process of bread. White wheat bread (WB) and bran-fortified wheat bread (BB) were consumed by eighteen panellists. The bolus was collected at four different mastication stages and characterized by properties of hydration, particle size, and texture. The results showed that there was no difference between the two bread samples in terms of swallowable bolus moisture. BB with a harder and denser texture produced more small particles and had a slightly shorter chewing time than WB during mastication. Moreover, bolus heterogeneity (D75/D25) indicated a distinct difference among mastication stages and revealed different disintegration pathways between the two samples: BB bolus exhibited a monotonous particle size reduction during mastication with reducing D50 and D75/D25; whereas, WB displayed a combination pattern of disintegration and agglomeration featuring relatively steady D50 and fluctuating D75/D25. It was concluded that bran fortification changed the bread breakdown pathways in terms of bread disintegration and bolus formation during the mastication process. This information offers new guidelines for fortifying innovative materials to manufacture foods specifically targeted for health.

Subthreshold chemesthetic stimulation can enhance flavor lastingness of a soft chewable candy.

In addition to taste and aroma components of a flavor, FEMA GRAS approved chemesthetic flavor ingredients deliver a trigeminal experience or chemesthetic effect and provide a third dimension to overall flavor experience. In this study, we explored the impact of chemesthetic stimulation on dynamic flavor perception, acceptability and salivation, with two base flavors (mint, watermelon), using a soft chewable candy as a model food. Each base flavor was augmented with three increasing levels of a mixture of chemesthetic flavor ingredients, which provided a cooling sensation; subthreshold, detection threshold, and supra-threshold levels. Thirty-six panelists were asked to rate the perceived flavor intensity of each sample during eating and after swallowing using time intensity analysis. Lastingness after swallowing was measured as the time for the flavor intensity to drop below 25% of the maximum intensity perceived during chewing. Compared with the control, the addition of chemesthetic flavor ingredients increased the perceived flavor intensity during chewing and the flavor lastingness after swallowing for both mint and watermelon flavor. These effects started from the addition of subthreshold concentration of chemesthetic flavor ingredients and further increased with increasing the concentration of chemesthetic flavor ingredients added. By adding the subthreshold concentration of chemesthetic flavor ingredients, the flavor lastingness was increased by 32% for mint flavor and 22% for watermelon flavor. The acceptability of these weak-flavored soft chewable candy test samples was significantly increased towards 'just right' with increasing concentrations of chemesthetic flavor ingredients, even at subthreshold level. However, chew time and saliva flow rate were not affected by the addition of chemesthetic flavor ingredients. The increased flavor lastingness by the addition of chemesthetic flavor ingredients could therefore be explained by perceptual interaction between chemesthesis and flavor perception.

Dynamic flavor perception of encapsulated flavors in a soft chewable matrix.

Encapsulation is commonly used to protect flavor compounds against adverse environmental and processing conditions or to provide controlled release in processed foods. Flavor compounds are released during eating and the release rate depends on food breakdown dynamics in the mouth. Two sequential studies were designed to explore the flavor perception of the same flavor in different encapsulation systems. The studies were focused on the interactions between encapsulation technology, particle size and breakdown processes in the mouth. A peppermint flavor was used as a model flavor and encapsulated with different technologies (spray drying, melt extrusion and fluidized bed drying). The encapsulated flavors and a selected combination were incorporated into a soft chewable candy, keeping the total flavor concentration the same for each sample. The chewable candy samples were presented to naïve panelists (n > 30) for the following two evaluations; (1) comparison of overall flavor perception with a 2-alternative forced choice test; and (2) dynamic evaluation of perceived flavor intensity over time during eating and after swallowing using time intensity. The results showed that the overall and dynamic flavor perceptions are greatly affected by the encapsulation technologies and particle sizes, and can be modulated by combining flavor particles produced by different encapsulation technologies depending on the application and desired flavor profile. The results also showed a large perceived flavor intensity variation between panelists, resembling variation among consumers. In an effort to better understand the relationship between the oral processing patterns and flavor perception, we used the JBMB® typing tool which gives four "Mouth Behavior" groups ("Chewers", "Crunchers", "Smooshers" and "Suckers") and explored to determine whether they would account for the variation. Compared with "Chewers" and "Crunchers", "Smooshers" tended to have a slower increase of flavor intensity during eating and a more gradual drop after swallowing. However, this needs to be confirmed with larger numbers of consumers (including suckers who were excluded in this study because they were not sufficient in numbers) and samples with a longer chew time.

Selection in mixtures of food particles during oral processing in man.

OBJECTIVES: Two processes underlie food comminution during chewing: (1) selection, i.e. every particle has a chance of being placed between the teeth and being subjected to (2) breakage. Selection decreases with particle number by saturation of breakage sites, and it depends on competition between smaller and larger particles for breakage sites. Theoretical models were tested which describe competition between various sizes X. In the one-way model, small particles cannot compete with larger ones because of their smaller height. In the two-way model, small particles may compete when piled between antagonistic teeth. DESIGN: Five subjects participated in one-chew experiments on cubes made of Optosil®. The critical particle number (nc(X)) at which saturation starts, and the number of breakage sites (nb(X)) were determined by varying particle numbers (nX) for single-sized cubes of 1.7-6.8mm. Using nc(X) and nb(X), the models predicted relationships between number of selected particles (ns(X)) and nX in one-chew experiments using simple mixtures with only two sizes. A fixed number (mean 6 or 26) of larger cubes (X=6.8 or 3.4mm) was mixed with various numbers (16-1024) of smaller cubes (X=4.8, 2.4 or 1.7mm), thus varying the factors X, nX, and possible particle piling (for X<4mm). RESULTS: The one-way model was largely followed with small numbers of smaller particles and the two-way model with large numbers. CONCLUSIONS: The two-way model applies to chewing a food which yields a loose aggregation of different-sized particles following an initial phase, whereas other circumstances may be favourable for the one-way model. As conditions of a food bolus can be approached by embedding hard Optosil particles in a soft medium, the models will, apart from dentistry, be of interest for controlling flavour release in food engineering.

Effect of surface composition on the flowability of industrial spray-dried dairy powders.

The surface composition of four industrial spray-dried dairy powders (skim milk powder, whole milk powder, cream powder and whey protein concentrate) was estimated by electron spectroscopy for chemical analysis (ESCA), and its influence on powder flowability was studied. It was found that skim milk powder flows well compared to the other powders because the surface is made of lactose and protein with a small amount of fat, whereas the high surface fat composition inhibits the flow of whole milk, cream and whey protein powders. However, the poor flowability of the powders with high surface fat coverage was drastically improved by removal of fat present on the surface through a brief wash with petroleum ether. The results obtained indicate that, although there are several parameters including particle size, which influence the flowability of powders, the flowability of powders is strongly influenced by the surface composition of powders, particularly for fat-containing powders.

Melting characteristics of fat present on the surface of industrial spray-dried dairy powders.

The melting characteristics of the fat present on the surface (surface free-fat) of two industrial spray-dried dairy powders (cream powder and whole milk powder) were investigated in comparison with those of other milk fat fractions present in the powder, such as free-fat from the interior of the powder particle (inner free-fat) and encapsulated fat. The melting characteristics of the milk fat fractions were studied by fatty acid composition, melting profile and solid fat content profile. The results indicated that all milk fat fractions including surface free-fat contained various triglycerides with melting points ranging from -40 to +40 degrees C. However, some fractionation was observed among the different milk fat fractions. The free-fat fractions (surface free-fat and inner free-fat) had a greater proportion of high-melting triglyceride species than the encapsulated fat. Furthermore, the high-melting triglyceride species present in the free-fat fractions were slightly accumulated at the surface of powder. This phenomenon was observed in both cream powder and whole milk powder and its effect on wetting time was established. This indicates that manipulation of the surface fat content during drying operation may hold the key to functionality improvement.

Solid-state characterization of spray-dried ice cream mixes.

The main physicochemical properties of spray-dried ice cream mixes (i.e. surface composition, wettability, flowability and microstructure) were analyzed. Emulsions contained 19-44% milk fat on a dry basis and included mixes with no added emulsifier and/or sucrose. The time necessary for complete wetting of the powders correlated with the amount of surface free-fat measured by means of solvent extraction. Non-micellar casein (sodium caseinate) showed to be a better co-encapsulant than micellar casein (skim milk) as demonstrated by surface fat coverage measured by electron spectroscopy for chemical analysis (ESCA). Emulsifiers influenced the fat surface composition of the powders by reducing the amount of surface protein due to their lower interfacial tension. Surface fat caused an initial overestimation of the particle size of the powders due to fat-related caking. Powders showed no flow before and after surface fat extraction which was attributed to fat-related caking and very small particle size (<80 microm), respectively.

Dietary fat and risk of postmenopausal breast cancer in a 20-year follow-up.

Dietary fat in midlife has not been associated with breast cancer risk in most studies, but few have followed women beyond one decade. The authors examined the relation of dietary fat, assessed by repeated questionnaires, to incidence of postmenopausal breast cancer in a cohort of 80,375 US women (3,537 new cases) prospectively followed for 20 years between 1980 and 2000. The multivariable relative risk for an increment of 5% of energy from total dietary fat intake was 0.98 (95% confidence interval: 0.95, 1.00). Additionally, specific types of fat were not associated with an increased risk of breast cancer. Furthermore, secondary analyses indicated no differences in breast cancer risk by estrogen receptor or progesterone receptor status. However, stratification by waist circumference indicated a significant decrease in breast cancer risk for participants with a waist circumference of 35 inches (88.9 cm) or greater (p-trend = 0.04). None of the latency intervals investigated were associated with an increased risk of breast cancer. In addition, fat intake before menopause was not related to risk of postmenopausal breast cancer. These results suggest a reduction in breast cancer risk for women with insulin resistance syndrome who consume high-fat diets and no association between specific sources of fat during midlife and risk of postmenopausal breast cancer.