Band 3, Heft 6

The two biopolymer proteins and polysaccharides are the key structural entities in food and pharmaceutical products. The design for liquid and semi-solid foods processing involves a complex and combined operations of heat transfer and fluid mechanics. These are strongly influenced by the thermal transitions and the rheological behavior of processing foods. In the present review a systematic discussion about the gelation, rheology of modified starches, and whey protein isolates are highlighted with an emphasis on various physico-chemical interactive effects. The studies are extended to protein and polysaccharide interactions and phase separations involved in the mixed system. Then the review has been made on protein-polysaccharide mixed gel systems citing few examples from the literature with respect to calorimetric and rheological characterization. Modeling studies developed by researchers are presented. Further the studies are directed towards the importance and exploitation of starch - whey protein isolate system in food processing and pharmaceutical industry.

High-pressure CO2 processing is one of the emerging preservation technologies designed to produce safe food, while maintaining its nutritional and sensory qualities. The effects of dense nitrous oxide processing parameters, including pressure (60-200 bar) and treating times (1-25 min) on yeast survival in apple juice were investigated. Experiments performed in multi-batch equipment at 36°C, confirm the effectiveness of the high pressure technology. N2O led to a complete yeast inactivation in 5 minutes, achieved at 100 bar and 36°C.As the inactivation hypotheses are concerning, some issues regarding N2O chemical nature, its interaction with lipids and cell membrane modification were discussed.Dense phase CO2/N2O processing can be an effective non-thermal alternative process for the pasteurization of apple juice.

Cassava is an important food crop, and equipment development for processing it in the developing world requires more research as industrial processing of cassava is still limited. Research efforts made by local engineers need scientific improvement to meet the Millennium Development Goals (MDGs), aimed at poverty reduction over a stipulated period of time with globally defined measurable indicators of progress. The World Summit on Sustainable Development (WSSD), the Report of the Commission for Africa (popularly referred to as the Tony Blair Report), and the New Partnership for African Development (NEPAD) are targeted at re-positioning Africa in the world economy. The need for rapid cassava processing equipment and new equipment development to significantly improve stages involved in its production process is highlighted in this paper.

In this paper, the physical properties such as length, width, thickness, geometric mean diameter, arithmetic mean diameter, mass, true volume, apparent volume, true density, bulk density, porosity, sphericity, surface area, shell ratio, aspect ratio, static coefficient of friction and mechanical characteristics namely firmness, hardness, adhesiveness, adhesive force and total positive area in puncture test were determined for kiwifruit of the Hayward variety. These properties are necessary in the design of the equipment for harvesting, processing and transportation, separating and packing. The results showed that the length, width, thickness, arithmetic mean diameter, geometric mean diameter, sphericity and aspect ratio of kiwifruit varied from 55.5 to 82.3 mm, 46.8 to 54.8 mm, 41.5 to 52.4 mm, 49.8 to 60.99 mm, 49.56 to 59.28 mm, 71.95 to 90.48% and 62.67 to 89.20%, respectively. While the surface area determined by McCabe et al.'s and Jean & Ball's formula, and surface area measured by experimental method changed from 77.11 to 110.34 cm2, 48.74 to 95.95 cm2 and 83.29 to 108.71 cm2, respectively. The values of the fruit's true volume, apparent volume, true density, bulk density and porosity were between 85-120 cm3, 63.69-109.01 cm3, 940-1040 kg/m3, 544.73-572.17 kg/m3 and 39.70-45.5%, respectively. Furthermore, the unit mass and peel ratio of kiwifruits ranged from 75.18 to 135.32 g and 8.91 to 12.51%, respectively. On four different surfaces, namely plywood, galvanized iron sheet, glass and fiberglass, static coefficient of friction varied from 0.34 on glass to 0.49 against plywood. The average firmness, hardness, adhesiveness, adhesive force and total positive area of peeled fruits were 229.42 g, 367.49 g, 716.48 g.s, -34.2 g and 11933.5 g.s, respectively. Corresponding values for unpeeled samples obtained 403.38 g, 2081.2 g, -3175.32 g.s, -118 g and 35757.22 g.s, respectively.

A roller mill was designed and evaluated using four equal size cylindrical rollers with their centers on vertices of a parallelogram. The relative speeds and opposite direction of rotation of the rollers allowed the discharge of the materials on them, and splitting took place in between the first pair of corrugated rollers. The broken seeds were directed towards the second and third nips where adequate size reduction was accomplished consecutively by smooth rollers. The milled products were separated into three fractions: chaff, flour and size larger than flour. The chaff and the flour are collected at different outlets, while the particles with sizes larger than flour are blown back into the hopper for further reduction. The mill was evaluated using three grains: maize, beans and soy beans at different combinations of evaluating parameters. The machine was able to mill grains to flour size without any leakage at the nip points. For all the grains, a wide gap set produced higher throughput than narrow, as well as fast feeding in smaller particle size and higher throughput. The results obtained from the evaluation showed that the machine is very capable of three-stage size reduction to produce flour, avoiding the feeding problems in three high roller mills. Sieve analysis of the milled product for each experiment showed uniform particle size.

The first aim of the study was to model the influence of water amount and air pressure on various batter properties using Response Surface Methodology. Batter quality was assessed through density, water content, colour, spreadability and fluorescence spectra. Quadratic models using two variables well represented spreading time, water content and final temperature, but they failed to fairly represent initial density, overrun and L*a*b* values. In addition, simplified models using a single variable also well represented the data: final density was modelled by a linear equation involving pressure, whereas initial density, water content and final temperature were modelled by a linear equation involving water amount. Spreading time was modelled using a quadratic equation using water amount. Experimental results were compared with expertise rules used by operators to control the industrial process. Indeed, operators often used water amount and air pressure as controlling variables. It was found that experimental results were in agreement with expertise rules. The second aim was to investigate the link between smart lab-measurement methods such as fluorescence spectroscopy and simple macroscopical properties used by operators such as water content, density, spreading time and colour. By applying hierarchical clustering analysis to NADH and tryptophan merged spectra, batter samples manufactured at various water amounts and pressure levels were clearly separated at a high level of discrimination. Neither water content nor spreading time were satisfactorily predicted from NADH or tryptophan spectra using PLS.

Experiments were conducted to study the drying characteristics of raw cauliflower florets. A mechanical tray dryer was used in this study. The samples were dehydrated at 60, 70, 80 and 90°C air temperatures with blanching pretreatment of two minutes in 0.75 per cent potassium metabisulphite. Drying characteristics were determined with the help of mass transfer data. Moisture content of cauliflower was found to decrease rapidly during the initial 150 minutes. Cauliflower behaved like a hygroscopic non-porous food material during the drying. Drying time of 330 to 510 minutes was required to reduce the moisture content from 92.50 per cent to 5.00 - 6.00 per cent. The moisture diffusivity during drying process was determined and found in the range of 2.54 x10-12 to 3.80 x10-12 m2/s. Quality of the dehydrated samples such as carbohydrate content, ascorbic acid retention and rehydration were also evaluated. The carbohydrate and ascorbic acid content in dehydrated samples ranged from 3.25 to 3.45 g per 100 g and 39.75 - 24.10 mg / 100 g as against 5.40 g / 100 g and 55.55 mg / 100 g respectively, in fresh vegetable indicating a significant loss of nutrients during processing. Product was found to be good in terms of appearance and taste up to 60 days for all the four temperature ranges.

The physical parameter results showed that the garlic geometric and arithmetic mean diameters ranged from 2.53 to 4.93, and 2.53 to 5.02 cm, respectively according to the bulb size categories. The cloves' length, width and thickness were 1.92 to 2.91, 0.78 to 1.32, and 0.69 to 0.99 cm, respectively. The surface and cross-sectional of areas ranged from 53.31 to 136.4 and 29.1 to 128.4 cm2, respectively. The number of cloves ranged from 18 to 51/bulb according to the bulbs size categories. Bulk density, repose angle and coefficient of contact surface values ranged from 892 to 1007 kg/m3, 41.52 to 45.04º, and 0.91 to 1.12, respectively, according to the bulb size categories.The chemical properties showed that the emptying (friction) angle ranged from 23.25 to 28.82º, where small bulbs recorded the highest values on the concrete surfaces, while the lowest values were recorded by the large bulbs on the iron surfaces. The friction coefficient decreased with increasing bulb size, where it was the highest (0.8) for the small bulbs on the concrete surfaces; on the other hand, the lowest values (0.36) were recorded for the large bulbs on the iron surfaces. The crushing load of the cloves ranged from 55.6 to 155.0 N, depending on the bulb size. The force required for loosening the cloves from the bulb ranged from 110 to 272 and 101 to 320 N on the horizontal and vertical positions of the bulbs.

Food products of perishable nature are needed to be preserved from spoiling using the precooling technique. Precooling is the process of cooling fruits and vegetables as soon as possible after the harvest and prior to the transportation over long distances to a cold storage warehouse and marketing. Therefore, an experimental investigation has been carried out to study the temperature variation of different food products viz. apple, papaya and grape during the precooling process. Forced air cooling of food products was done by placing the particular food item inside a 4 m long rectangular air duct of 300 mm x 300 mm section. The temperature of cold air was in a range of 4-5 oC and the air velocity varied from 1.6 m/s to 4.1 m/s. The temperature of food product was measured at different radial locations inside the product. The effect of air velocity on the temperature profile of food product was observed and it has been found that the proper choice of cold air velocity can reduce the cooling time of certain food product up to 33 percent, thus, resulting in the saving of energy.

Two enzyme assisted processes were studied in this work, protein extraction and hydrolysis, aiming phenylalanine (Phe) removal from corn. For protein extraction, a protease of Bacillus liccheniformis was used and the effect of temperature (55 and 60°C) and time (1, 5, 15 and 24 h) was evaluated. For Phe removal, a pancreatin was used for hydrolyzing corn proteins and the activated carbon (AC) was the adsorbent support. In this case, the influence of several parameters was estimated, such as protein extract concentration, E:S ratio, use of freezedrying, protein: AC ratio and way of using AC. The efficiency of Phe removal was evaluated by second derivative spectrophotometry, measuring the Phe content in the corn flour as well as in the hydrolysates after AC treatment. The results showed that the time and the temperature influenced the protein extraction yield and the best results were obtained at 55°C, after 5 h, 15 h and 24 h of reaction, having reached an average extraction yield of 85.3%. The removal of Phe, changed from 68.63 to 97.55%, and its final concentration from 18.80 to 240.75 mg/100 g hydrolysate. The condition that produced the highest Phe removal was the one using a protein extract concentration = 1%, E:S = 1 or 2%, pH 9, temperature = 25°C, protein: C = 1:88.5, using three types of AC and freezedrying (hydrolysates H1 and H2). However, this condition presents some disadvantages such as the use of freezedrying, which highly raises the process cost, and a non-controlled and non-repeatable reaction. Among the samples with no freezedrying stage and more controllable reaction (H9 and H10), H10 is the best one, since it showed smaller Phe content (149.27 mg/100 g) using three types of AC, which is advantageous from the technical point of view. The reduction of the protein: AC ratio, for these two hydrolysates (H9 and H10) was not beneficial for Phe removal, leading to higher Phe content.

The antimicrobial and antioxidant potentials of hydrodistilled essential oil and oleoresin (obtained using acetone as a solvent) of tailed pepper were carried out by different techniques. The results obtained from antioxidant activity measurements of essential oil and oleoresin against mustard oil were measured for duration of 28 days in terms of peroxide, thiobarbituric acid, total carbonyl and p-anisidine values. The results obtained from butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) was similar to both the oleoresin and essential oil. In addition, the inhibitory action in linoleic acid system was studied by monitoring accumulation of peroxide concentration. The radical scavenging capacity of both essential oil and oleoresin on 2, 2'-diphenyl-1-picrylhydrazyl (DPPH) radical were (71.2%) and (69.77%) respectively at 25 µL/mL. It was relatively lower in comparison with synthetic antioxidants (BHA-96.41%; BHT- 95.91%). The results obtained from reducing power, chelating effect and hydroxyl radical scavenging effect was also supported the antioxidant of essential oil and oleoresin. The tailed pepper essential oil and oleoresin showed 100% mycelial zone inhibition against Penicillium viridicatum at 3000 and 2000 ppm respectively in the poison food method. It is interesting to note that the essential oil revealed 100% clear zone inhibition against Aspergillus flavus at all tested concentrations. The chemical characterization of tailed pepper essential oil by GC and GC-MS resulted in the identification of 44 components accounting for 97.8% of the oil.

A near-infrared spectrometer equipped with surface interactance optical fiber probe (400-1100 nm) was used to determine the fat content in intact sardine Sardinops melanostictus which is considered one of the important fish species of world aquaculture as well as human food source. The fat contents were 2.64–25.52 % and fish weight ranges were between 45.23g and 133.76g. Partial least square regression was used to develop predictive equations for fat where two models (with and without multiplicative scatter correction known as MSC) showed relatively good performances with regression coefficients higher than 0.9 and errors below 1% on a fresh weight basis. Results showed that NIR interactance was a suitable non-destructive screening method for fat content in intact small pelagic fish like sardine.