Band 3, Heft 4

The effects of temperature, relative humidity and molecular structure on the crystallization process within amorphous solids have been explored. Lactose and sucrose were spray dried, and the products were exposed to different and relative humidities. To investigate the effect of temperature, experiments were conducted at both room temperature and 40oC. The rate of the crystallization was more than doubled for every increase of temperature by 10oC, up to three times for the case of lactose. These results are consistent with the picture of the process as an activated rate one. The effect of increasing relative humidity (RH) was observed to increase the rate of crystallization up to a threshold value, after which the rate was no longer affected by relative humidity. This threshold was found to be 51% for sucrose, at room temperature, which was lowered to 32% at 40oC. Lactose and sucrose, which have the same molecular weight of 342 g/mol but different molecular structures and thus glass transition temperatures, were exposed to similar conditions. The difference in molecular structures had little effect on the overall rate of the crystallization process for the same material temperatures, in contrast with the predictions of the Williams Landel Ferry equation, which suggests that the rate of crystallization is a function of the difference between the material temperature and the glass transition temperature.

The aim of this study was to employ iota-carrageenan (IC) and wheat protein (WP) as an emulsifier alternative to egg yolk in a model mayonnaise system. A solution of 0.1% IC and 4% WP was prepared and used as an emulsifier in five different mayonnaise formulas. All mayonnaise treatments were evaluated and compared based on lightness and yellowness (i.e., L and b values respectively) at 4, 23, and 40°C. In addition, an adaptive neuro-fuzzy inference system (ANFIS) was used to model and identify the properties of the resulted mayonnaise, with the temperature and ratios. Experimental validation runs were conducted to compare the measured values and the predicted ones. The L value of the mayonnaise produced from different emulsifiers decreased at the lower storage temperature. The b-value was significantly the highest for mayonnaise formulated from 100% egg yolk. The comparison showed that the adoption of this neuro-fuzzy modeling technique (i.e., ANFIS) achieved a very satisfactory prediction accuracy of about 98%.

The quality characteristics of wastewater of the Sudanese Fermentation Industry (El-Hassaheissa- Gezira State) were investigated. The study indicated that wastewater contained higher amounts of nutrients. The percentage of protein of the separator waste and the main drain waste were found to be 0.5% and 0.7%, respectively. The molasses waste contained higher amounts of total solids (56.8 mg/l) while separator waste, filter waste and the main drain waste contained 0.4 mg/l, 0.4 mg/l and 0.24 mg/l, respectively. The molasses waste had a higher BOD (640 mg/l) and COD (4500 mg/l) values compared to the separator waste, filter waste and main drain waste which contained 250 mg/l, 450 mg/l and 148 mg/l BOD values, respectively. However, the COD values of separator waste, filter waste and main drain waste were 250 mg/l, 160 mg/l and 80 mg/l respectively. Different wastewater samples contained relatively high concentrations of macro-and micro-elements and mineral salts. The microbiological analysis indicates absence of staphylococci and coliform in most of the wastewater samples.

The objective of this study was to investigate the effect of heat treatment of milk on the quality characteristics of Jibna-beida (white cheese). The heat treatment methods used included pasteurization of cow milk at 65oC for 30 min, and boiling of cow milk at 102oC for 15 min. The microbiological analysis indicated that raw milk contained high counts of total viable microbes, coliforms, staphylococci, yeast and mould. However, all these microbial groups were highly reduced in pasteurized and boiled milk. Jibna–beida was prepared using the three types of milk: raw, pasteurized and boiled. The raw milk cheese contained: 43.0% moisture, 12.5% ash, 20.16% protein and 56.48% total soluble solids, while the pasteurized milk cheese contained: 50.9% moisture, 10.5% ash, 17.63% protein and 48.76% total soluble solids and the boiled milk cheese contained: 48.5% moisture, 13.4% ash, 15.4% protein and 55.75% total soluble solids. During storage, the pH of all cheese samples decreased and the acidity increased. The microbiological analysis of the three types of cheese indicated that the microbial load of raw milk cheese was higher when compared with those of pasteurized and boiled milk cheeses. The sensory evaluation revealed acceptance of the three types of cheeses with preference to the raw milk cheese than the other two types of cheese.

Investigation was carried out on the effect of processing conditions such as temperature, pressure and porosity on permeability of palm fruit cake. It was observed that increasing the temperature of the crude palm oil from 30 to 75°C, pressure from 2.88 to 3.82 kPa and porosity from 9.2 to 27.3% increases the permeability of the palm fruit cake. The statistical analysis of the effects of the processing factors on permeability indicates that temperature and porosity are significant at 99.99% while pressure was significant at 95%. A permeability model applicable to the practical palm oil expression was also developed in the study.

The internal cooling of fish has been studied on the basis of Newton’s cooling law. Experiments were conducted by cooling of the Indian major carp (Catla catla) of different weights with ice in an insulated box. Exponential model describing cooling of objects having irregular shape has been investigated. The developed model could predict the fish cooling with ice within a percent error of 0.74. The thermal properties of fish cooling with ice have been evaluated. The cooling data such as cooling coefficients, average surface heat transfer coefficient, thermal resistance, thermal capacitance, half cooling time and seven-eighth cooling time were determined for individual fish. The results show that the half cooling time and seven-eighth cooling time increased and the cooling rate decreased with increase in the weight of fish, respectively. Thermal resistance was independent of fish weight and having an average value of 1. 22 °C W-1. Thermal capacitance increased with fish weight and ranged from 665.8 to 4639.3 J °C-1. The average surface heat transfer coefficient of fish cooling with ice ranged from 11.68 to 34.41 W m-2 °C-1.

The focus of this study involved the application of an effective methodology to estimate decimal reduction of two main food-borne pathogens (i.e., Salmonella and Listeria) in frozen cooked chicken products using surface pasteurization. A quick and effective approach to estimate the surface temperature of the product was proposed using the Page equation and the evaluation of pathogenic destruction on the large-size and small-size frozen steamed chicken products. The samples were in the frozen form and treated as if they were post-contaminated by Salmonella and Listeria. The pasteurization temperatures in the steam oven were varied at 70, 75, 80, 90 and 100 degree Celsius. The Page equation performed well to accurately predict the surface temperature profile of the different product sizes. The steam treatment was very effective in heating up the pasteurized products and resulted in similar temperature profiles regardless of product size. The relationship between the model constant coefficient and pasteurization temperature followed the Arrhenius expression. The substitution of the predicted surface temperature profile to the process lethality equation facilitated quick estimation of pathogenic destruction on the sample surface. The different sizes of the chicken products only slightly affected the pasteurization time. However, the pasteurization time to achieve that same decimal reduction varied significantly between the two different target pathogens. The simplicity and effectiveness of this approach did not only eliminate multiple experimental repetitions and simplify the estimation of pathogenic destruction, but also provided and effective minimal processing procedure for frozen cooked chicken pasteurization of two sizes of steamed products while retaining the desirable quality of end products after surface pasteurization.

This research aimed to develop a prototype of an evaporative dehydrator and demonstrate the effect of quick evaporative dehydration on the physiochemical properties of banana paste. The study was divided into 2 parts. The first part was focused on the development of the evaporative dehydrator prototype. After several modifications, the prototype of an evaporative dehydrator was successfully constructed to enable the variation of banana paste sample prior to evaporation using two types of evaporative stresses (i.e., atmospheric and vacuum conditions). The second part was to study the effect of evaporative dehydration on the physiochemical properties of banana paste comparing vacuum and atmospheric conditions. The temperature setting for the heating section was varied at 30, 40, 60, 80, 100 and 120 degree Celsius and the physiochemical alteration of the banana paste sample was monitored. The peroxidase enzyme was found to be active in all treatments. The evaporative cooling in the vacuum treatment caused the temperature of the final product to be lower than that of the atmospheric treatment. The moisture content also seemed to be lower and the water activity was less. Although the acidity remained stable and was not differentiable between the two treatments; the different evaporative conditions had a profound effect on other physiochemical properties, especially the external appearance of the final product. The visual appearance was determined by the Hunter indices (L, a, and b) and delta E (overall color change). As the operating temperature increased, the delta E in both treatments increased. The sample in the vacuum treatment became darker (lower L-value) and more intense in yellow color (higher b-value). This was hypothesized to be the result of product condensation due to moisture loss. The a-value decreased as the operating temperature increased and there was no significant difference between the two treatments. The viscosity of the final product had a unique profile regarding the operating temperature variation. It appeared to be more viscous than the fresh sample at low temperature. For the higher temperature setting, the viscosity decreased as the temperature increased. Enzymatic and non-enzymatic chemical reactions might be responsible for the alteration of the flow characteristics of dehydrated sample rather than the sole effect of moisture reduction.

The effects of different drying methods on the cellular structure of carrots were examined. Carrots were dried by vacuum drying, freeze drying and oven drying in combination with microwave pre-drying. Dried and fresh untreated samples were analysed by light microscopy and environmental scanning electron microscopy (ESEM). The cellular structure of vacuum dried as well as microwave pre-dried samples was found to be very different from that of fresh samples. Most, if not all, of the original microstructure was lost during drying with these techniques, though traces of original structure were preserved on external surfaces. Most of the original microstructure was preserved in the freeze dried carrot. ESEM was also used to observe the behaviour of the dried samples in an atmosphere of increasing humidity and showed that dried tissues did not regain their original cellular structure though some turgidity was regained by the freeze dried samples.

Colour formation in technical and model sucrose solutions was investigated resulting in a novel kinetic approach of MAILLARD reaction during thermal processing of sugar solutions. Presented results describe new aspects of the non-enzymatic browning reaction (MAILLARD reaction). Two temperature depending pathways of colour formation were found. Both reaction mechanisms are based on the formation of a-dicarbonyl compounds, the key intermediates of colour formation.Discussing temperature dependence of colour formation, a change on MAILLARD reaction mechanism takes place at 100.4 °C. Above this temperature the colour formation is strongly accelerated. Activation energy of the non-enzymatic browning energy for temperatures from 65 ° to 100.4 °C amounts 77 kJ/mol. In this temperature range, D-glucosone is the most important a-dicarbonyl compound for studied reaction systems. Above 100.4 °C, activation energy is equal to 112 kJ/mol and 3-deoxyosone is the dominant colour formation intermediate. Achieved results bridge the gap between the termination step of a MAILLARD reaction –i.e. of colour formation (represented by its activation energy) and intermediates formation (reaction kinetics). In particular, a change of colour formation mechanism with reaction temperature was confirmed by specific formation of two a-dicarbonyl compounds, responsible for MAILLARD reaction in technical sugar solutions.

The effect of addition of xanthan gum (0.05, 0.1, 0.15, 0.25% weight/volume) on the formation and rheology of whey protein isolate (WPI)-xanthan gum gels has been investigated at neutral pH. The elastic modulus (G') values of the gelling test were compared. Low concentration of xanthan added (<0.05%,w/v) has a synergistic effect on the gel strength depend on phase separation, so that whey proteins concentrated in their phase and finally mixed gels with xanthan would be stronger than WPI gels. At higher xanthan concentration (> 0.05%, w/v), antagonist effect was observed by reducing the connection between clusters of whey protein by xanthan, so aggregation disruption and a related decrease in (G'). The phase separation microstructure of WPI-stabilized emulsion containing xanthan gum added has been investigated by rheology and confocal laser scanning microscopy. Xanthan was stained with Fluorescein 5(6)-isothiocyanate (FITC). Low xanthan concentration addition lead to depletion flocculation and increasing the xanthan concentration cause to increase the viscoelasticity of aqueous phase, so retarded macroscopic phase separation over period investigated. Structural changes in emulsion were observed in viscoelastic properties of separated phase in the rheometer. The CLSM image shows different phase which have different viscoelastic properties; xanthan-rich region transforms into the spherical shape which has the lowest interfacial energy and gradually two separated ultimately.

The moisture sorption behavior of pectin films formulated with different sorbitol content was evaluated and films with different equilibrium moisture contents were obtained. Different models were used to describe the moisture sorption isotherms (MSI) of pectin films, sorbitol and pectin powder. Based on changes observed in MSI, sorbitol was found to strongly interact with pectin polymers. Incorporation of sorbitol in pectin films resulted in lower equilibrium moisture contents at low to intermediate water activities (aw), but much higher moisture contents at aw > 0.53. Estimates of monolayer moisture values (1.53 – 3.81 g H2O kg-1 solids) were obtained by the application of Guggenheim-Anderson-DeBoer (GAB) model. A differential mechanical analyzer (DMA) was used for mechanical properties of formulated films while a differential scanning calorimeter (DSC) was used for thermal properties and glass transition temperature (Tg). With both DMA and DSC tests, the strong plasticizing action of water and sorbitol was evident. Tg vs. moisture content data were successfully fitted to the Fox empirical model. Multi-frequency DMA measurements provided estimates for the apparent activation energy (Ea) of the second glass transition in the range of 131-184 kJ/mol; the values for Ea decreased with increasing sorbitol concentration. Water vapor permeability (WVP) and mechanical properties of the films were also analyzed under varying sorbitol and moisture contents. Increasing moisture or addition of sorbitol to pectin films increased the elongation at break, but decreased the tensile strength, modulus of elasticity and Tg, and increased WVP of the films.

Combined effects of heat and pulsed electric fields treatment (20 and 40oC, 0-800 µs at 30 kV/cm) on microbial inactivation inoculated in egg whites were studied. Pulsed electric fields treatment time and processing temperature had profound effects on microbial inactivation. Pulsed electric fields treatment with a bipolar pulse (2 µs wide), an intensity of 30 kV/cm, a frequency of 100 Hz, the processing temperature of 40 oC and treatment time for 800 µs, was sufficient to achieve pasteurization conditions using S. enteritidis , E. coli and S. aureus, common spoilage and pathogenic micro-organisms in egg products. This treatment produced a non-significant (p>0.05) increase in foaming capacity and stability and an increase (p<0.05) in emulsifying capacity and stability. Surface free sulfhydryls and hydrophobicity of egg white proteins increased with the increment of the PEF treatment time due to the partial unfolding of egg white proteins. Almost 50 % of trypsin inhibitory activity of ovomucoid in liquid egg white was decreased when the treatment time extended to 800 µs. These results suggested that combined treatment of heat and pulsed electric fields could be applied to process liquid egg whites to get desired products.

Double fortified salt prepared with various formulations of iodine and microencapsulated iron has been investigated for stability in a five-month period, under actual field conditions of storage and distribution, in the south coastal and north highland regions of Nigeria. A control of iodated salt and fifteen 500g sample packets of double fortified salt, prepared in duplicate, were sealed in polyethylene bags. These samples, and a datalogger for monitoring temperature and humidity, were packaged into a typical bundle which was overwrapped with polyethylene film and inserted into the distribution network starting from a salt manufacturer's facility to the consumer. Iodine retention values of up to 79% were obtained when iodated salt was used and 64% when potassium iodide premix was used. Less than 20% of the ferrous iron was oxidized to ferric iron, and about 25% of the iron in formulations with sodium ferric EDTA (NaFeEDTA) reduced to ferrous iron. Double fortified salt with ferrous fumarate was generally more stable than those prepared with the other iron premixes. The polyethylene film overwrap of salt packs in the bundles provided a significant protection from ambient humidity. Iodine and the ferrous iron were protected in salt, double fortified with iodine and microencapsulated iron, during distribution and retail in typical tropical conditions in Nigeria's coastal and northern highlands.

Aqueous two phase extraction was employed directly to the cell homogenate of Spirulina platensis for the downstream processing of C-phycocyanin. This enables integrating the process steps of cell removal, extraction and concentration into a single unit operation of aqueous two phase extraction. The effect of different parameters such as molecular weight, tie line length, volume ratio and neutral salt (NaCl) were studied employing PEG 4000/potassium phosphate system and PEG 1000/sodium sulfate system to select the best system among the two. For PEG 4000/potassium phosphate system at 13.12% TLL, and volume ratio 0.45, 90.34% yield of phycocyanin with purity of 0.73 was obtained. In the case of PEG 1000 /Na2SO4 system at 34.98 % TLL and volume ratio of 1, 97.62 % yield of phycocyanin with a purity of 0.41 was achieved. Effect of NaCl concentration shows a significant decrease in K of phycocyanin in PEG 1000/Na2SO4 system as compared to PEG 4000/potassium phosphate system. PEG 4000 and potassium phosphate system was found to be better than PEG 1000 and sodium sulfate system for the extraction and purification of C-phycocyanin.

Nanotechnology will become one of the most powerful forces for innovation in the food packaging industry. One such innovation is biobased nanocomposite technology, which holds the key to future advances in flexible packaging. Biobased nanocomposites are produced from incorporation of nanoclay into biopolymers (or Edible films). Advantages of biobased nanocomposites are numerous and possibilities for application in the packaging industry are endless. A comprehensive review of biobased nanocomposite applications in food packaging industry should be necessary because nanotechnology is changing rapidly and the food packaging industry is facing new challenges. This provides a general review of previous works. Many of the works reported in the literature are focused on the production and the mechanical properties of the biobased nanocomposites. Little attention has been paid to gas permeability of biobased nanocomposites. In regard to extensive research on Edible film, this article suggests investigating the replacement of biobased nanocomposites instead of Edible films in different areas of food packaging.