Volume 4, Issue 7

A study was conducted to assess the effectiveness of pulsed electric field (PEF) inactivation of a heterogeneous community of microbes. The aim was to assess the impact of process parameters on an indigenous population of microbes present in milk, rather than pure cultures used in other studies. Tests over an electric field strength range of 10 – 40 kV/cm and 10 to 120 pulses per millilitre showed that high electric field strength and pulse number inactivated microbes by up to approximately 2 log. Inoculum size affected PEF effectiveness when only a few pulses were applied. A significant log-reduction was achieved against the indigenous microbes found in milk that were apparently recalcitrant to commercial pasteurization. Microbial inactivation was more extensive when E. coli was not added to the indigenous population, indicating that the added pure culture was more resistant than the indigenous microbes. The milk fat content had a significant negative effect on the extent of log-reduction for indigenous microbes, when 2% and 18% levels were compared.

The production of tchapalo remains more or less an empirical process. For the improvement of the product quality, there is a need of more knowledge on this traditional process and the beer characteristics. The alcoholic fermentation is one of the most steps which most determines the quality of the beer. In this study, the characteristics of the traditional starter and the evolution of temperature, ethanol, sugars and organic acids were assessed at small-scale production during alcoholic fermentation of tchapalo. Brewers used traditional starter at the rate of 0.76-0.88 % when it was dried or at 2.38 % when it was not. When the wort was at 36.6-39.3 °C, the starter was added to initiate the fermentation. Temperature decreased to 34.6-36.5 °C at the end of the fermentation which was concluded after 7.6 h to 8.4 h. Sugars were consumed during the fermentation but it remained 12.9 to 16.57 g/L of reducing sugars and 8.02 to 9.12 °Brix of TSS in the final product. Ethanol content increased from 0.02-0.35 % (v/v) in the wort to 3.5-4.59 % in the beer. The oxalic, citric, tartaric, malic, lactic, fumaric and propionic acids were found in the wort and in tchapalo and increased or decreased during fermentation differently from one site to another. But, the acetic acid was not always detected in both the wort and the beer.

Effects on drying and other acceptability parameters when slices of tomatoes were subjected to different pretreatments before initiating the process of drying were studied. The study also included observation of effects of inherent moisture levels in the drying tomato on the attributes such as color, texture, shrinkage and appearance. The pretreatments consisted of solutions in water, of sugar (1%), calcium chloride (1,2 % ), common salt (2%), ascorbic acid (0.75%) and sodium benzoate (0.1%). The slices of tomato, 1 cm thick, were soaked in the specific solutions separately for 3, 6 and 12 hours. Untreated tomato slices served as control. Drying was stopped when tomato slices attained moisture levels of 30% and 10%. Drying rate (mr = m ebx where: mr - moisture ratio; m - model constant; b - drying rate; x – time, minute) ranged between -0.007 (sugar solution 1%) and -0.029 (control). Pretreatments did in fact influence the shrinkage both at 10 and 30 % moisture levels. Effect on shrinkage was more pronounced at 30 % than 10 % moisture level. Visual assessment and photographs suggest that pretreatments with calcium chloride and sodium chloride had better texture and visual appeal than other pre-drying treatments. Duration of drying to reach 10% moisture level ranged between 180.0 and 241.67 minutes. Variations were observed between samples for parameters re-hydration ratio and water activity (0.462 – 0.550). It is suggested that pre-drying treatments do affect the different parameters that were studied and can help in improving the visual appeal and acceptability.

In Malaysia, the dragon fruit is widely commercialized. It is extensively used in the food industry. Their use as constituents of juices, jellies, marmalades, jams, wine, beverages, etc. generates a consumer market with an increasing demand. This work aims to obtain rheological data of dragon fruit juice which is essential in optimizing equipment design, process control, and consumer acceptability of a product. In the present study, dragon fruit juice with concentrates of (10 and 12oBrix) was prepared. The rheological behavior of these concentrates was studied in the temperature range of 5, 10, 15, and 40oC. Dragon fruit juice was found to exhibit non-Newtonian, pseudoplastic behavior. Samples on both concentrations were adequately described by the rheological model. The effect of temperature on dragon fruit juice is best described by the applicability of the Arrhenius model related to apparent viscosity, ?a.

The properties of pummelo juice were studied by measuring its chemical and physical composition. Pummelo fruit juice was freeze-concentrated to a concentration varying from 10 to 50 °Brix for investigation at temperature ranging from 6 to 75 °C. The fresh pummelo juice compositions in terms of moisture content, ash, fat, protein, fibre, carbohydrates, and vitamin C are comparable to existing literature. The water activity, pH and acidity were predictable linearly by its concentration measured in °Brix. The density of pummelo juice was well-predicted using linear regressions with a single parameter (i.e., concentration), giving R2>0.983 and with a temperature at R2>0.921. The density of pummelo juice showed stronger dependence on its concentration than on the temperature. With multiple linear regressions, the density could be predicted by the equation, with an R2 of 0.9877. As such, these predictions are useful in the juice processing industry as densities variant by concentration and temperature are important during the pasteurization process.

The effect of moisture content and drying temperature of Vitellaria paradoxa Gaertn kernels on some of its physical properties was investigated. The kernels which were harvested at a moisture content of about 60% (wet basis) and hence prone to high post harvest losses from two ecological zones of Cameroon (Bangoua in West province and Tchabal in Adamawa province) were dried in a forced convection dryer at 40oC, for 6, 20, 48, 72 and 96 hours to give moisture contents ranging from 10 to 60% wet basis. Ten trees from each of the zones were carefully selected to serve as sources for the ripe kernel bearing shea fruits that were used as samples for this study. For each parameter studied, a sample population of 30 kernels selected at random per tree was used. The results obtained revealed that there was a significant difference in the physical properties of the kernels from different trees irrespective of the locality. The bulk density, true density, sphericity and porosity varied non-linearly with the moisture content. Kernels with larger masses showed a different variation pattern of bulk density and porosity with moisture content compared to the lighter kernels. The variation of the bulk density, sphericity, porosity of sheanut kernels with moisture content and temperature was satisfactorily modelled with empirical equations. The samples underwent considerable shrinkage (up to 35%) during the drying process. Three empirical models were used to describe the shrinkage behaviour of the kernels and it is proposed that these models could be incorporated in drying models.

Changes in color and total phenolic content of different persimmon varieties (Türkay, Hachia, Morali and Fuyu) are investigated during dehydration. In all varieties, L* values were decreased during dehydration. Fresh and dehydrated Morali persimmons had a darker color than the other varieties. Fresh Fuyu and dehydrated Hachia persimmons had higher a* values. Increased a* value indicated that sample color became red. In fresh fruit, b* values of astringent varieties were higher than non-astringent persimmons. During dehydration, b* values of non-astringent persimmons (Morali and Fuyu) were decreased continuously. Hue* values of Fuyu variety were lower than the other varieties. In the dehydration process, hue* values of all varieties were decreased. In phenolic contents of dehydrated Hachia and Türkay varieties, 93.55% and 79.12% reduction were observed respectively. In sensory evaluation, dehydrated astringent and non-astringent varieties had similar scores for astringency and taste characteristics. Fuyu, Türkay and Hachia varieties had similar color scores and their scores were higher than Morali samples.

In the chemical, pharmaceutical and food-processing industries, the drying operation is a major intermediate step in the production of finished or semi-finished products. There are a great many drying processes and types of equipment, such as dryers with immersed channels; the main advantage of this type of dryer is the homogeneous distribution of the drying air, made possible by dihedrons, a special device for introducing the air. The basis tool for dimension, a drier with immersed channels, is the control of the dehydration of the product, and the distribution function residence time of the particles inside the column. In the present study, a model and thus an indirect measurement of dispersion coefficients of solids were proposed in contrast with previous studies where the variation of dispersion coefficient has often been disregarded in the granular flow models. The comparison of calculations with measurements gave an indirect measurement of the longitudinal and transversal variable coefficients as a function of the position in the column. It is concluded that it is necessary to account for the variation of dispersion coefficients during the granular flow in the column to obtain a correct description of their flow. It is worth noting that this indirect measurement proves that the transversal dispersion coefficient varied much more than the longitudinal one.

The aim of this study was to employ whey proteins isolate (WPI) and carboxymethylcelulose (CMC) as stabilizers in beverage production and to evaluate viscosity of the products. Three beverages were formulated using 6% WPI combined with three different concentrations of CMC (0.1, 0.5, and 1%). The combination of 6% WPI/1.0% CMC was selected and added to three different ratios of pure orange juice (50:50 "T1," 40:60 "T2," and 15:85 "T3"). The apparent viscosity decreased as shear rate and temperature increased. Additionally, the apparent viscosity for the same treatment at certain shear rate/same temperature increased after storage. In addition, an adaptive neuro-fuzzy inference system (ANFIS) was used to model and identify the viscosity of the resulted beverages. Experimental validation runs were conducted to compare the measured values and the predicted ones. ANFIS models achieved an average prediction error of viscosity of only 9%. It is believed that this approach can be applied to predict many other parameters and properties in beverage industry.

This work involved the removal of phenylalanine (Phe) from wheat flour which followed three steps: 1. protein extraction using an alkaline protease from Bacillus licheniformis; 2. protein hydrolysis by the action of a commercial enzyme (pancreatin or Panc) in association with a crude enzymatic extract obtained from pineapple peel (CE); 3. use of activated carbon (AC) as adsorbent. The effect of some parameters, such as order of enzyme action, pH and reaction time, was evaluated. The efficiency of Phe removal was assessed by second derivative spectrophotometry, measuring the Phe content in the wheat flour as well as in its hydrolysates after AC treatment. The results showed the advantage of using CE for 1h30min followed by Panc for 3h30min, at pH 7.0, producing 66.28% of removal and a final Phe content of 522.44 mg/100g of hydrolysate.

Many food materials such as pasta, potatoes, starch, corn, soybeans, food gels etc. exhibit glass transition in the range of industrial temperature and fluid content values during transport processes such as drying, sorption, cooking, frying etc. Glass transition plays a critical role in affecting the fluid distribution profiles inside the food and average rate of fluid uptake by the whole food matrix. Yet this phenomenon is not included in most modeling studies that are primarily based upon Fick's law of diffusion. The purpose of this communication is to elucidate that Fick's law is valid only when the food is in glassy or rubbery states. Near glass-transition, the relaxation time of polymers is of the order of diffusion time. Thus, time-dependent conformational changes in food biopolymers add an extra stress term to fluid flow. Keeping track of this stress term is also the key to predict quality changes (related to food texture, physical state and crust formation) in foods via modeling. Based upon the average moisture and temperature at a given instant, even if the entire food matrix exists in a specific mechanical state in an average sense, its different sub-regions may be glassy, rubbery or in glass transition state. For example, during sorption, as a fluid front penetrates through a glassy food matrix, regions ahead of the front will be glassy. Regions in the proximity of the moving front would be undergoing glass transition and the regions already saturated by the fluid would be in a rubbery state. In the proximity of the moving front, where glass-transition is taking place, the fluid flow behavior is non-Fickian. During drying of biopolymers these regions will be in reverse order with the outer surface in a glassy state, center in a rubbery state and the middle region in transition state. Here a continuum mechanics based modeling approach is presented that can be used to predict fluid profiles and normalized stress profiles in all three states (glassy, rubbery and transition).

Rheological properties of tomato concentrate were evaluated using a wide-gap rotational viscometer (Brookfield Engineering Laboratories: Model LVDV-II) at different temperatures of 20, 30, 40, 50, and 60oC, at concentration of 18, 12.18 and 8.04 % total solids, and at appropriate shear rate(1-100 RPM). The power law model was fitted to the experimental results. The values of flow behaviour index (n) were found less than unity (0.23 to 0.82) at all the temperature and the concentration indicating shear-thinning (pseudoplasticity) behaviour of the concentrate. The correlation between the observed consistency coefficient ranging from 0.09 to 65.87 Pa.sn and the inverse absolute temperature has been exhibited by Arrhenius model. Consistency coefficient increased exponentially with increase in the concentration. Statistical model was used for prediction of the consistency coefficient as a function of temperature and concentration which showed a good agreement (r2=0.99) between experimental and theoretical values. The magnitude of activation energy were found to be in the range of 8.6 to 14.08 kJ/mol.K.

This paper reviews the application of atomic force microscopy (AFM) to the study of starch structures, including both macrostructure of starch granules and the nanostructure of molecular chains. It introduces the different techniques of sample preparation and discusses what AFM could observe. The paper summarises the present situation of the application of AFM in the study of starch structures and guides the direction for further research.