Volume 2, Issue 3

Spouted bed is suitable for drying of coarse particles which are Group D of Geldart’s particle classification. Malaysian grown paddy was used as a Group D sample in a lab-scale spouted bed dryer. Drying was carried out in two different internal structures of the dryer, namely with or without the installation of a draft tube, and at several drying temperatures, air flow rates as well as bed heights. Spouted bed drying kinetics of paddy presented in drying curves showed only induction and falling rate periods, without constant drying rate period. The highest drying rate was achieved when paddy was dried without draft tube at low bed height, high drying temperature and air flow rate.

Spontaneous fermentation of maize produces lactic acids resulting in souring or acidification with associated improvement in taste, flavour and texture of the derived products. When combined with nixtamalization and cowpea fortification, it is expected to improve the nutritional quality and product functionality of maize based foods and as well introduce variety to maize processing. This study was carried out to investigate the changes in souring development, nutritional quality and functional properties during spontaneous fermentation of cowpea-fortified nixtamalized maize. A 2 x 3 x 3 factorial experimental design, with fermentation medium (water, coconut water), fermentation time (0, 24, 48 hours) and cowpea level (0, 15, 30 %) was performed. Nixtamalized maize was prepared by boiling whole maize in 1 % lime solution for 30 minutes, steeped in excess lime, milled into meal and kneaded into a dough using water or coconut water. The blends were fermented for the specific times and analysed for pH, titratable acidity, water absorption capacity, colour, protein and ash. The presence of lime and cowpea influenced the pH, titratable acidity, water absorption, colour, protein and ash content of the fermented cowpea-fortified maize. Addition of cowpea increased most of the studied indices whiles pH of all the blends decreased (6.15-4.45) with a corresponding increase in titratable acidity (0.008-0.045 g/100g lactic acid) with increase in fermentation time. There was however no significant (p<0.05) difference in the effect of fermentation medium on these indices suggesting that coconut water could be used as an alternative fermentation medium for maize dough fermentation without any effect in souring development. Fermentation and cowpea fortification can therefore be used to increase the nutritive value of nixtamalized maize with acceptable souring and product quality characteristics.

The performance of nano-filtration (NF) for separating phenolic compounds from sugar in apple juice was studied using 1 and 0.25 kDa molecular weight cut-off (MWCO) spiral wound membranes. If these phenolic compounds could be recovered, they could stabilize the juice from haze formation or be added as antioxidants to foods and beverages in order to increase their health properties. Batch experiments were conducted on a pilot scale rig using a diluted clear apple juice concentrate. For the 1 kDa MWCO membrane, the research determined the effect of operating conditions on process efficiency and membrane fouling. The concentration of polyphenolics on the retentate side increased by a factor of up to 4 and the sugar concentration increased by 1.5 times under optimum conditions of lower temperature (30oC), acidic pH (2), lower trans-membrane pressure (5 Bar) and higher initial sugar concentration (20 oBrix). Despite the increase in polyphenolics in the retentate, there was little difference in the phenolic composition between retentate and permeate solutions. As the molecular mass of the rejected phenolics was smaller than the membrane cut-off, this indicated that the rejection was related to the formation of a secondary membrane formed as a result of fouling. A mass balance of polyphenolics in the final retentate and permeate compared with the initial feed solution indicated that up to 4.3 gm of polyphenolics were bound per m2 of membrane. The permeate solutions collected from the 1 kDa MWCO membrane were then filtered using a 0.25 kDa MWCO membrane. Most phenolic compounds were retained by the membrane and the concentration increased by a factor of up to 2. Catechin, rutin, phloridzin and quercetin derivatives were concentrated on the retentate side. However, around 20 - 40% of chlorogenic acid and epicatechin was observed on the permeate side. It is concluded that membrane separation represents a potentially efficient and cost-effective technology to separate the phenolic fraction of fruit juice in a form suitable for use as a functional ingredient.

The use of agro industrials products cassava starch and sugar cane bagasse present a great potential as substrate and support, respectively, showing low production costs for amylases production under solid-state fermentation by Aspergillus niger LPB 28. The effect of various factors was examined and some variables were optimized to ?-amylase and amyloglucosidase production. Inoculum rate in different concentrations (105, 106, 107 and 108 spores/g of cassava starch) were used to inoculate the solid substrate for the SSF. The material was supplemented with nitrogen sources; calcium source and micronutrients solution. The ratios of cassava starch to sugar cane bagasse (1/1; 1.5/1; 1/1.5; 1/2; 2/1; 1/3; 3/1) were tested and the initial moisture content varying 80, 85 and 90%. Cultivation was carried out at temperatures 25, 30 and 35ºC for 48, 60 and 72 h. Study of influence of pH initial in SSF was conduced in pH 4.0, 5.0, 6.0, 7.0 and 8.0. Statistical analysis was carried out using the software STATISTICA 5.1 (StatSoft, Tulsa, OK, USA). A 32 complete factorial design (2 factors, 3 levels and 9 experiments) was used to study the effect of the factors in ?-amylase and amyloglucosidase production. The results showed cassava starch and sugar cane bagasse at the ratios of 2/1 was the best for optimum production of ?-amylase and amyloglucosidase. The maximum yield (?-amylase 1732.95 U/g of cassava starch and amyloglucosidase 2044.94 U/g of cassava starch) was achieved with optimized process parameters such as incubation period (60 hours), moisture level was 90%, inoculation rate (105 spores/g of dried material), pH 4.0 and fermentation temperature (30ºC). The nitrogen source (KNO3) also enhanced the ?-amylase and amyloglucosidase activities. In kinetic characterization of enzymes the Michaelis-Menten constant KM and maximum velocity Vmax (KM 10.84 g/l, Vmax 3.42 g/l) for ?-amylase and KM 11.32 g/l and Vmax 5.18 g/l for amyloglucosidase.

Water absorption characteristics of two newly-released maize hybrids, Obatanpa and Mamaba, during soaking were measured at four temperatures of 30, 40, 50 and 60ºC. The absorption kinetics followed the Fick's law of diffusion during the first hours of soaking. The values determined for water diffusion coefficients varied from 7.31 x 10-12 to 9.33 x 10-12 m2/s and from 6.30 x 10-12 to 8.25 x 10-12 m2/s for Obatanpa and Mamaba respectively. An Arrhenius–type equation was used to relate the diffusion coefficient of Obatanpa and Mamaba to temperature, and the energy of activation for Obatanpa and Mamaba was estimated. The values determined were 6.54 kJ/mol and 6.82 kJ/mol for Obatanpa and Mamaba respectively.

Chicken nuggets were either deep fat fried at three temperatures (150, 170 and 190oC) for 1 to 4 min or oven baked at three temperature levels (200, 220 and 240oC) for 5 to 25 min. The effects of these cooking methods on mass transfer characteristics of chicken nuggets were evaluated. Moisture loss profiles in the breading and core portions of the product were significantly different. There was a rapid moisture loss from the breading portion within the first 2 min of deep fat frying or within the first 15 min of oven baking followed by considerably reduced rates. Moisture loss in the core region changed only slightly in the early stages of frying or oven baking but increased afterwards. Moisture diffusivity in the breading region was evaluated using analytical solution of Fick’s second law diffusion equation. Values of moisture diffusivity were from 20.93x10-10 to 29.32x10-10 m2/s for deep fat frying and from 1.90x10-10 to 3.16x10-10 m2/s for oven baking. The activation energies were 8.04 and 25.7 kJ/mol for deep fat frying and oven baking, respectively.

The main objective of this work was to determine the influence of different hydrophilic gums on the stability and shelf life of bread dough during frozen storage. Bread dough containing different level of hydrophilic guns were submitted to mechanical freezing at -18° C and stored frozen for up to 60 days. Two types of hydrophilic gums in different combination were tested: for specific loaf volume of breads made from frozen dough and for its shelf life study by measuring its moisture level at 3, 24, 48, 72 and 96 hrs after baking of frozen dough bread. Specific loaf volume was significantly affected by the hydrophilic gums, Arabic gums showed better effect than CMC. Frozen storage of the dough negatively affected the specific loaf volume of the bread. The addition of 3% Arabic Gum had a beneficial effect on the specific loaf volume and moisture contents of the frozen dough bread.

A static heat exchanger was used to study the extent of heat induced fouling in the device due to passage of cow, buffalo, double toned and reconstituted milk for a period of one hour. The static heat exchanger was developed to simulate the flow condition of an actual indirect type heat exchanger employed in the processing plant. Flow rate of 2x10-7 m3 s-1 was selected as this gave the same 1.052x10-3 m3 m-2 flow rate/surface area ratio as applicable to indirect double tube heat exchangers used in the industry. Both milk with fat and with fat removed by centrifugal separation were used. Fresh and recycled milk were the other two factors used in the study of fouling. It was found that there was no significant difference in fouling deposit formation between fresh and recycled milk, but significant difference existed between milk with fat and milk with fat removed. Reconstituted milk was found to have significantly lower deposit compared to cow, buffalo and double toned milk.