Glazing effects on bread crust and crumb staling during storage.

The uses of cornstarch, egg white, skim milk and shortening as glazes on bread surfaces were investigated for its ability to reduce bread staling. Four concentrations of glazes were applied to sweet bun surfaces. Bread crumb and crust samples were measured for its firmness and moisture during storage. The rates of change in firmness and moisture contents of crumb and crust with storage time were analyzed by comparing with nonglazed breads as control. While both crumb and crust firmness and the crust moisture content increased with storage time, crumb moisture content decreased significantly (P PRACTICAL APPLICATIONSThe use of glaze materials in baked products may provide more than an aesthetic function of creating appearance appeal. This research shows that glazing of breads reduces bread staling through its ability to retain crumb moisture and reduce crumb firming. This finding provides means of improving bread quality in terms of textural properties and its shelf life by means of processing and with no alter in ingredients' formulation

Rheological and textural studies of fresh and freeze-thawed native sago starche.

The viscoelastic and textural properties of freshly prepared and freeze-thawed sago starch–sugar gels were studied in comparison with other native starches from corn, wheat, tapioca, and potato. The gelatinisation and retrogradation properties of starches were studied using a DSC while the pasting properties of starch–sugar mixtures during the cooking period were studied using a starch pasting cell. The freeze-thaw stability of gels was evaluated by gravimetric measurements of the water of syneresis. The different starches gave properties which varied following to their botanical sources. High-amylose cereal starches (wheat and corn) produced harder gels, while low-amylose root starch (tapioca) produced softer gels. Sago and potato gels showed close similarities in their viscoelastic and textural characteristics. Although the freeze-thaw cycle greatly increased the viscoelasticity and hardness of these two gels, reheating at high temperature significantly reduced these negative effects and resulted in partial recovery of the gel structures. Sago starch produced gels with very low syneresis and high cohesiveness, implying its potential use as a gelling agent in the frozen food industries

Direct and indirect power ultrasound assisted pre-osmotic treatments in convective drying of guava slices

Application of ultrasound to osmotic dehydration of guava slices via indirect sonication using an ultrasonic bath system and direct sonication using an ultrasonic probe system was studied. Pre-treatments were designed in three osmotic solution concentrations of 0, 35, and 70 °Brix at indirect ultrasonic bath power from 0 to 2.5 kW for immersion times ranging for 20–60 min and direct ultrasonic probe amplitudes from 0 to 35% for immersion times of 6–20 min. The calculated ultrasound intensities from calorimetric ultrasound power dissipated indicated that direct sonication was more intensive than indirect sonication. The general linear model (GLM) showed that ultrasound input (power and amplitude), osmotic solution concentrations, and immersion time increased the water loss, solid gain, and total colour change of guava slices significantly with P < 0.0005. Indirect sonication in osmotic solutions contributed to high water loss and solid gain with acceptable total colour change than direct sonication. Applying ultrasound pre-osmotic treatment in 70 °Brix prior to hot-air drying reduced the drying time by 33%, increased the effective diffusivity by 35%, and decreased the total colour change by 38%. A remarkable decrease of hardness to 4.2 N obtained was also comparable to the fresh guava at 4.8 N

Rheological and textural studies of fresh and freeze-thawed native sago starch-sugar gels. I. Optimisation using response surface methodology.

A three-factor–three-level Box–Behnken design was adopted to study the simultaneous effects of two compositional variables (6–8% sago starch and 25–35% sugar) and one processing variable (shearing speed of mixer at 20–50 rpm) on textural and rheological properties of gels. Analysis of variance (ANOVA) was performed to evaluate the potential interactive and quadratic effects between these variables. Sago starch and sugar levels both increased gel stiffness and viscoelasticity. Shearing, on the other hand, reduced gel stiffness and viscoelasticity. Ridge analysis was performed to estimate the values of these variables which maximised and minimised the textural parameters of hardness, gumminess, resilience, cohesiveness, and springiness. Pearson correlations among various rheological and textural properties of gels were studied. The processing conditions that contributed to an optimum gel setting were found at sago starch of level of 7.69%, sugar of 30.29%, and shearing speed of 45.86 rpm

Uniaxial die compaction of food powders

This paper presents a study of uniaxial die compaction of food powders for typical food powders such as maize powder and maize grits as well as a universal binder known as microcrystalline cellulose or Avicel. This method of compaction is widely applied in the industry as it can investigate the compressibility and compactability characteristics of powders prior to handling, storage, packaging, and transportation. In the current context, a cylindrical uniaxial die of 20 mm was used to compress the powders into compact. Pressures ranging of 30 and 160 MPa were applied to the uniaxial die using a universal testing machine. It was found that Avicel powder showed the highest compactability characteristic, ability to form bonding easily. Whereas, compactability of both the coarse maize and fine maize were quite similar, which may be due to the similar chemical composition. The data were then validated using an established compression equation. The asymptotic residual modulus value reduced as the ability of the food powders to form plastic junctions - assuming that they existed - increased. For the tensile strength test, Avicel compact showed the greatest tensile strength, many times that of fine maize and coarse maize compacts. However, between the fine maize and coarse maize, fine maize had higher tensile strength which may be due to its smaller particle size, as well as the fact that the contact area may be increased, and consequently may form a more coherent compact. The results indicate that this simple approach can be used to understand the compressibility and compactability characteristics of food powders which are essential for engineering and technology application

Modelling of rheological behaviour of soursop juice concentrates using shear rate-temperature-concentration superposition

The effect of temperature and concentration on rheological behaviour of freeze dried soursop juice concentrates were investigated using a rheometer over a wide range of temperatures (10–70 °C) and concentrations (10–50 °Brix) at shear rates of 0–400 1/s. The Power law is the best fitted model to the rheological data due to the high value of coefficient of determination (R2 = 0.9989). The soursop juice concentrates exhibited shear thinning or pseudoplastic behaviour with n < 1. The consistency coefficients dependency on temperature and concentration were well described by Arrhenius relationship and exponential relationship respectively. The flow activation energy of soursop juice concentrates were 8.32–30.48 kJ/mol. The superposition technique with Power law model sufficiently modelled the overall rheological characteristics of soursop juice concentrates into a single master curve using shift factors based on double shifting steps with R2 = 0.9184. This technique also showed that the soursop juice concentrates increases in viscosity and pseudoplasticity behaviour with concentration

Development of nutraceutical product

The aim of this study was to discuss the development of nutraceutical product which includes the current market trends, challenges, and exploitation of natural resources through various processing. Wet granulation and dry granulation techniques were adopted for such processes. Wet granulation covers high shear mixing granulation, fluidized bed granulation, and twin screw granulation. Dry granulation covers roll compaction and uniaxial die compaction. These techniques were compared and reviewed in terms of physical, chemical and toxicity studies. The physical study considered the particle size, density, morphology, flowability and dissolution. The chemical study discussed on the active ingredients in the nutraceutical products and the toxicity study was presented by investigation carried out on rats. There is a high potential for development of nutraceutical product. By understanding the various techniques of processing and characterisations, more nutraceutical products can be marketed

Effects of grinding time on rheological, textural and physical properties of natural peanut butter stored at different temperatures

The effects of ultrahigh speed grinding process duration of 2–4 min and its storage temperature on rheological, textural and physical properties of natural peanut butter produced from peanuts of Virginia and Spanish varieties were investigated. Both types of peanut butter samples exhibited food suspension with multimodal particle size distribution, fitted adequately to the Casson model and demonstrated nonNewtonian shear-thinning behavior with apparent yield stress. The storage (G′) and loss (G′′) modulus decreased as a function of grinding time and temperature. Grinding time and storage temperature gave significant effects on all the responses (P < 0.05) while peanut variety only has impact on the particle size distribution. Identical trends were observed for the natural peanut butter from both Virginia and Spanish peanut varieties

A review on rheological properties and measurements of dough and gluten

The field of rheology has seen a wider application in the food industry recently although, it is a complex concept and that most food systems possess non-ideal characteristics. Nevertheless, the rheological behavior of foods are able to be determined using various techniques and equipment. Studies on rheological properties related to dough and gluten are often challenging due to its variance in nature and high dependence on many factors. This study attempts to give a review on the various types of experimental techniques and set-up used in quantifying rheological properties of dough and gluten. The rheological properties are defined and the behaviors are described by inducing stress and strains in small and large deformation studies

Rheological characterisation of Malaysian varieties of sweet potato doughs using large and small deformation measurements

The rheological properties of sweet potato doughs at different mixing times were studied. In the large deformation extension test, extensibility parameters including dough length at fracture, measured, and actual forces acting on dough strips were obtained for calculating the stress-strain data. For the small deformation test, both storage and loss modulus of dough were studied. The extensibility of dough from sweet potato flour increased to its peak at five minutes mixing time before decreasing illustrating an optimum mixing time. The variety of VitAto which has a higher protein content of 5.7 g/100 g has higher values of all the extensibility parameters as compared to Bukit Naga and Okinawan. In terms of flow-behavior index, all sweet potato doughs displayed n values from 1.82 to 2.11, indicating strain hardening behaviors similar to wheat flour doughs. The small deformation tests were not able to identify the optimum mixing time, although in general, illustrated that sweet potato doughs were essentially elastic or recoverable. The Pearson correlations of large and small deformation tests showed that the rheological parameters were positively correlated among themselves in the evaluation of the effect of mixing time to rheological properties of sweet potato dough