DESIGN GUIDELINES FOR CYCLONE IMPROVEMENT

ABSTRACT

There is a potential for improving cyclone separators by design and operating conditions. Secondary flow detrimental to dust separation can be avoided by proper gas inlets, dimensioning of body and swirl, or by use of a flow guide in the area of separation. Cyclone and bin are to be treated as one unit. Scavenging of the bin is most effective for high effiency. Cut sizes smaller than 1 μm can be realized with a cyclone separator unit consisting of a preseparator, a battery of small cyclones, and a scavenging cyclone with gas recirculation. Such arrangements are capable to cope with dust streaks and to make positive use of dust agglomeration. These principles are applicable also for big cyclone batteries as used behind rotary dryers for wood chips, etc.     

DUST STRANDS IN CYCLONE SEPARATORS AT LOW DUST CONCENTRATION

Abstract

State of the art in calculating a cyclone separator is the application of the equilibrium theory and taking the formation of dust strands into account as well. The latter process does not depend on particle size mainly. An ideal flow pattern for the formation of dust strands is the so called Dean-vortex: it is being realized favorably in the axial flow cyclone. A dust strand can be produced down to a raw gas concentration C₀ ≈ 10^?5. Then, it is being exhausted through one or few holes in the mantle of the axial cyclone applying bleeding of about 10 % of the volume flow Separating its dust in a bin cyclone and recirculating the binflow gas to the main, axial cyclone completes this high performance cyclone separator. Dimensional analysis shows that the clean gas concentration c₁ mainly depends on the swirl W_tan/w_ax, the raw gas concentration c₀and on Reynolds number. For usual dust conditions a clean gas concentration c₁ ≤ 50 mg/m³ is feasible.     

Physical, Chemical and Sensory Changes in Irradiated Fresh Pork Packaged in Modified Atmosphere

The effects of irradiation dose (0, 0.5 and 1.0 kGy), headspace oxygen (0, 10 and 20% O₂, balance nitrogen) and storage temperature (5, 15 and 25°C) on the physical, chemical and sensory changes in fresh pork were studied using factorial design experiments. Irradiation in the absence of oxygen extended the sensory shelf life of pork from 9 to 26 days at 5°C and from & lt; 2 to 2 days at 25°C. Oxygen in the package headspace combined with irradiation adversely affected physical, chemical and sensory characteristics of the end product.     

QUALITY OF COFFEE CREAMERS AS A FUNCTION OF PROTEIN SOURCE

Many U.S. consumers add a sweetener or creaming agent to their brewed coffee. An ideal creamer, when added to coffee, should remain stable, dissolve readily, and provide whitening ability. In general, these properties are imparted by the protein component. Four different proteins – sodium caseinate, isolated wheat protein, soy protein isolate and whey protein concentrate – were used to formulate coffee creamers, individually and in combination, and the resultant creamers were evaluated for functionality. Coffee creamers containing plant proteins had significantly greater apparent viscosity but lower L* values than did creamers made with dairy proteins. Creamers made with higher concentrations of isolated wheat protein exhibited syneresis, whereas no syneresis occurred if sodium caseinate was the predominant protein. Only the creamer formulated with soy protein isolate alone exhibited feathering when added to hot, brewed coffee. These results indicate that coffee creamers can be formulated with plant proteins and sodium caseinate.     

Modified Atmosphere Packaging Affects Ascorbic Acid, Enzyme Activity and Market Quality of Broccoli

Reduced ascorbic acid (RAA) content, total chlorophyll and green color retention, enzyme activities and texture changes were followed in broccoli spears packaged in polymeric film and nonpackaged during 96 hr storage (10°C). Concentrations within packages monitored by gas chromatography were (CO₂,) 8% and (0²) 10%. RAA retention, moisture content, total chlorophyll and color retention were greater in packaged broccoli. No differences were found between packaged and nonpackaged broccoli for ascorbate oxidase and peroxidase activities, or texture.     

Properties of Algin/Calcium and Salt/Phosphate Structured Beef Rolls with Added Gums

Ten polysaccharide gums at two levels (0.5 and 1.0%) were individually incorporated into algin/calcium (AC) and salt/phosphate (SP) structured beef rolls (<6% fat) prepared with 15 and 30% added water. Cook yield, pH, bind and textural properties were evaluated. Each gum had specific effects on properties of beef rolls. For example, kappa-carrageenan improved (P<0.001) cook yields and maintained or improved bind and texture of raw and cooked samples of both meat binding systems. Cook yields of AC products were improved with gellan gum, while yields of SP products were improved with iotacarrageenan. Other gums (xanthan, guar, pectin, carboxymethyl cellulose) improved water holding (cook yields) but had detrimental effects on product texture.     

TEMPERATURE MAPPING IN A POTATO USING HALF FOURIER TRANSFORM MRI of DIFFUSION

Two dimensional temperature maps of a potato during heating were obtained using magnetic resonance imaging (MRI) techniques. the molecular pseudo self-diffusion coefficient of the water in the potato was used as a temperature indicator. Two dimensional half Fourier transform spin-echo and Generalized Series reconstruction techniques were used to reduce data acquisition time to about 10 s/image and to improve temperature mapping resolution. Thermocouples were implanted into the sample so that temperature and MRI data were acquired simultaneously. the error in MRI measurements caused by noise and the time delay required to collect each data set was less than 0.84C with 0.75 mm² resolution. the average variation between MRI and thermocouple measurements was less than 0.5C. This is a promising new technique to noninvasively study heat transfer and to measure thermal properties of food materials.     

COMPOSITION OF CARBOHYDRATES AND CONCENTRATION OF β-GALACTOSIDASE OF COMMERCIAL FROZEN YOGURT

Commercial frozen yogurt samples were analyzed for composition, β-galactosidase activity, and microbial quality. The composition of protein, fat, sugars, other carbohydrates, and total solids varied considerably among the 11 brands tested. All samples contained high levels of lactic acid bacteria (> 6. 0 log cfu/mL), as well as active β-galactosidase but the enzymatic activity varied greatly (1.04 – 43.12 ONP units) among samples. A significant correlation (r = 0.785) existed between β-galactosidase and lactic acid bacteria concentrations. The major sugars in samples were sucrose (0–12.7%) followed by lactose (2.31–4.25%) and glucose (0.74–2.49%). The sugar extraction method developed for the HPLC analysis gave reliable and reproducible data, despite the fact that frozen yogurt samples contained a wide variation in fat, protein, and total solids contents.