Relating the stickiness property of foods undergoing drying and dried products to their surface energetics

Stickiness is a common problem encountered in food handling and processing, and also during consumption. Stickiness is observed as adhesion of the food to processing equipment surfaces or cohesion within the food particulate or mass. An important operation where this undesirable behavior of food is manifested is drying. This occurs particularly during drying of high-sugar and high-fat foods. To date, the stickiness of foods during drying or dried powder has been investigated in relation to their viscous and glass transition properties. The importance of contact surface energy of the equipment has been ignored in many analyses, despite the fact that some drying operations have reported using low-energy contact surfaces in drying equipment to avoid the problems caused by stickiness. This review discusses the fundamentals of adhesion and cohesion mechanisms and relates these phenomena to drying and dried products.

Botany of the southern states. In two parts. Part I. Structural and physiological botany and vegetable products. Part II. Descriptions of southern plants. Arranged on the natural system. Preceded by a Linnæan and a dichotomous analysis.

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Improving availability, promotion and purchase of fruit and vegetable and non sugar-sweetened drink products at community sporting clubs: a randomised trial

BACKGROUND: Amateur sporting clubs represent an attractive setting for health promotion. This study assesses the impact of a multi-component intervention on the availability, promotion and purchase of fruit and vegetable and non sugar -sweetened drink products from community sporting club canteens. We also assessed the impact the intervention on sporting club revenue from the sale of food and beverages. METHOD: A repeat cross-sectional, parallel group, cluster randomized controlled trial was undertaken with amateur community football clubs in New South Wales, Australia. The intervention was conducted over 2.5 winter sporting seasons and sought to improve the availability and promotion of fruit and vegetables and non sugar-sweetened drinks in sporting club canteens. Trial outcomes were assessed via telephone surveys of sporting club representatives and members. RESULTS: Eighty five sporting clubs and 1143 club members participated in the study. Relative to the control group, at follow-up, clubs allocated to the intervention were significantly more likely to have fruit and vegetable products available at the club canteen (OR = 5.13; 95% CI 1.70-15.38), were more likely to promote fruit and vegetable selection using reduced pricing and meal deals (OR = 34.48; 95% CI 4.18-250.00) and members of intervention clubs were more likely to report purchase of fruit and vegetable (OR = 2.58 95% CI; 1.08-6.18) and non sugar -sweetened drink (OR = 1.56; 95% CI 1.09-2.25) products. There was no significant difference between groups in the annual club revenue from food and non-alcoholic beverage sales. CONCLUSION: The findings demonstrate that the intervention can improve the nutrition environment of sporting clubs and the purchasing behaviour of members. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry: ACTRN12609000224224 .

Optimization of co-current spray drying process of sugar-rich foods. Part I - Moisture and glass transition temperature profile during drying

A steady state mathematical model for co-current spray drying was developed for sugar-rich foods with the application of the glass transition temperature concept. Maltodextrin-sucrose solution was used as a sugar-rich food model. The model included mass, heat and momentum balances for a single droplet drying as well as temperature and humidity profile of the drying medium. A log-normal volume distribution of the droplets was generated at the exit of the rotary atomizer. This generation created a certain number of bins to form a system of non-linear first-order differential equations as a function of the axial distance of the drying chamber. The model was used to calculate the changes of droplet diameter, density, temperature, moisture content and velocity in association with the change of air properties along the axial distance. The difference between the outlet air temperature and the glass transition temperature of the final products (AT) was considered as an indicator of stickiness of the particles in spray drying process. The calculated and experimental AT values were close, indicating successful validation of the model. (c) 2004 Elsevier Ltd. All rights reserved.

Measurement of glass-rubber transition temperature of skim milk powder by static mechanical test

Stickiness behavior of skim milk powder was investigated based on the mechanical property of the material during the glass-rubber transition. A thermally controlled device was developed for the static mechanical test. This device was attached to a texture analyzer, and skim milk powder, which was used as a model sample, was tested for its glass-rubber transition temperature (Tg-r) using static compression technique (creep test). Changes in compression probe distance as a function of temperature were recorded. Tg-r was determined, in the region where changes in the probe distance were observed, by using linear regression technique. The effect of sample quantity, compression force, and heating rate on the determination of Tg-r was investigated. All these parameters significantly influenced the Tg-r determination (p < 0.05). The Tg-r of skim milk powder measured by this novel technique was found closely correlated to its glass transition temperature (T-g) measured by DSC.

Modeling dimensional shrinkage of shaped foods in fluidized bed drying

Three particular geometrical shapes of parallelepiped, cylinder and sphere were selected from cut beans (length : diameter = 1: 1, 2:1, 3: 1), potatoes (aspect ratio = 1:1, 2:1, 3:1) and peas, respectively. The dimensional shrinkage behavior was studied in a batch fluidized bed at three drying temperatures of 30, 40 and 50C. Relative humidity of hot air was kept at 15%. Dimensional shrinkage was plotted using a nondimensional moisture ratio and the shrinkage behavior of the selected foods was modeled with simple mathematical models.

A laboratory experiment, based on the maillard reaction, conducted as a project in introductory statistics

A simple laboratory experiment, based on the Maillard reaction, served as a project in Introductory Statistics for undergraduates in Food Science and Technology. By using the principles of randomization and replication and reflecting on the sources of variation in the experimental data, students reinforced the statistical concepts and techniques introduced to them in lectures before the experiment. The experiment was run simultaneously by several student groups, using the same materials. Comparing the results of their analyses of variance, students became aware of the difference between P values and significance levels in making statistical decisions. In the experiment, the complete randomized design was applied; however, it is easy to adjust the experiment to teach students simple regression and randomized block designs.

Alkali hydroxide-induced gelation of pectin

The mechanism of pectin gelation depends on the degree of methoxylation. High methoxyl pectin gels due to hydrophobic interactions and hydrogen bonding between pectin molecules. Low methoxyl pectin forms gels in the presence of di- and polyvalent cations which cross link and neutralise the negative charges of the pectin molecule. Monovalent cations normally do not lead to gel formation with high methoxyl pectin solutions free of divalent cations, especially Ca. The present study found that alkali (NaOH or KOH) added to high methoxyl pectin leads to gel formation in a concentration-depended manner. It was also found that monovalent cations (Na and K) induce gelation of low methoxyl pectin and the time required for gel formation (setting time) depends on the cation concentration. The results indicate that a combined char-e neutralisation and ionic strength effect is responsible for the monovalent cation-induced gelation of pectin. (C) 2003 Elsevier Ltd. All rights reserved.