Pavel Kadlec

Potentials of separation membranes in the sugar industry

There are described some applications of membrane separation, e.g. reverse osmosis in the treatment of sugar beat press water, recovery of salt from waste brine at a sugar decolorization plant or microfiltration and ultrafiltration of raw sugar juice, as an alternative to chemical purification process. The last case is completed by original experimental work. Samples were treated with cross flow micro- and ultrafiltration on ceramic membranes having porosity 20 and 50 nm. The changes in the content of sucrose, invert sugar and lactic acid were observed, resulting in increasing the juice purity from the initial value 89% to the final value 91‐92%. In addition, permeate can be a subject for direct crystallisation after thickening to produce the final product. Retentate purity decreased to 87‐88%. For nanofiltration tests (NF) there has been designed a special stainless steel cross-flow dynamic cell for pressures up to 4 MPa. The preliminary NF tests were focused on testing different commercial flat polymeric membranes (Hydronautics-Nitto Denko, Osmonics-Desal).

Application of continuous chromatographic separation in sugar processing

Abstract The work deals with application of continuous counter-current chromatographic separation station in sugar technology. There are two main targets in this study: (1) Changes in sugar technology: simplification of sugar processing by sucrose crystallization from chromatographic extract without any previous demanding chemical processing and (2) higher valorisation of waste material and intermediates from sugar processing by isolation of high-quality substances. The chromatographic pilot plant KCHS-SMB-8, which was developed by the Department of Carbohydrate Chemistry and Technology ICT Prague and the firm MIKROPUR Hradec Kralove, was used for this purpose. Experiments deal with suggestion and verification of main operation conditions during chromatographic separation of technical sugar solution. The process was focused on separation of various model mixtures of sucrose/salt and sucrose/betaine. Results provide a basic data for further research and development for industrial use.

Processing of yellow pea by germination, microwave treatment and drying

A high content of α-galactooligosaccharides affects the nutritive value of legumes. In agreement with papers concerning the effect of germination on the composition of various grain legumes, our results show that the most important decrease of α-galactooligosaccharides (raffinose family oligosaccharides — RFO) in the yellow pea (Pisum sativum) occurs during the first 3 days of germination. Wet germinated peas were treated by microwave (MW) energy and dried by hot air at 80°C. The benefit of MW treatment is shortening and improvement of drying. Proposed processing steps for the modification of nutritional properties of pea include: (1) germination of pea seeds (3 days); (2) MW treatment of germinated seeds; (3) drying by hot air; (4) grinding of dried seeds; and (5) preparation of meal from the modified pea flour.

Application of high-pressure processing for preservation of germinated legumes

High-pressure processing on germinated legume seeds (pea, chickpea, lentil, green gram) was studied. Total microflora was decreased: in three days germinated pea seeds decreased from 2.4 × 106 CFU/g to less than 10; in two days germinated chickpea seeds decreased from 1.6 × 105 CFU/g to less than 10; in three days geminated lentil seeds decreased from 3.4 × 107 CFU/g to less than 10; and in three days germinated green gram decreased from 1.4 × 109 to 1.8 × 102 after treatment of high pressure 500 MPa for 10 min. High pressure treated germinated seeds were stored in tap water (pea) and in citric acid pickle pH=2.5 (chickpea) or pH=2.0 (lentil, green gram) at 4–8 °C. The total microflora increased during 21 days storage in pressurized germinated pea seeds to 7.5 × 104 CFU/g and in green gram to 3.5 × 105. The contents of microorganisms in pressurized germinated chickpea and lentil seeds were under detection limits of methods used.

Microorganisms baroinactivation of germinated mung bean (green gram) seeds

It is possible to describe the pressure degradation of microorganisms as being analogous to thermal inactivation. Equation for baroinactivation is derived from thermal death time (TDT) model D p = D pref 10(pref-p)/z p , where D pref is decimal reduction time at the reference pressure (min), p ref is the reference pressure (MPa), z p is the pressure increase (MPa) required to reduce the D p value by a factor of 10. This method was used for the calculation of baroinactivation model parameters of the total number of microorganisms of pressurized germinated mung bean (green gram) seeds (Vigna radiata (L.) Wilczek). Microbial contamination of germinated mung bean (green gram) seeds can be effectively decreased by treatment at a high pressure of 400 MPa, time of pressurization 5 min.

Cheese whey tangential filtration using tubular mineral membranes

Membrane separation techniques are extensively used in dairy industry both for milk and cheese whey processing. However, cheese whey might still be considered as a problematic waste despite its high content of many valuable substances, such as proteins, lactose or minerals, which can be further used, e.g. in human nutrition, pharmacy or biotechnologies. Another problem, which food technologists have to face, is variable quality, composition and properties of food materials bringing high demands on manufacturing industry. In this paper, filtration kinetics and separation efficiency during purification and fractionation of cheese whey (sweet and salty) from Czech dairies by pilot-plant filtration (Bollene, France) was studied using tubular membranes (Membralox, USA). Various mineral membranes’ cut-offs were tested and all experiments ran in the retentate recycling mode. The obtained mass concentration factors were between 1.9 and 16.5. Steady state fluxes were calculated from the experimental data using a mathematical model. Fine ultrafiltration on a 5 kDa membrane gave steady state fluxes of 14–19 L m−2 h−1. The coarse pre-filtration on 100 nm, 200 nm or 500 nm membranes showed various permeate fluxes between 22 L m−2 h−1 and 153 L m−2 h−1. Despite the high pore sizes of the used membranes, lactose was partially rejected by all membranes tested.

GROWTH RATE OF SUCROSE CRYSTALS

Abstract One of the basic parts of the sugar production technology is crystallization. The value characterizing this process, i.e. the crystallization rate is a complex function of a variety of factors. The principal ones are: supersaturation. mixing, temperature, viscosity, crystal content in the massecuite, and in technical sugar solutions the effect of non-sugars has to be added. An important role is played by the geometrical layout of the laboratory equipment or industrial apparatus.

MEASUREMENT AND COMPUTATION OF PHYSICO-CHEMICAL PROPERTIES OF SUGAR SOLUTIONS

Abstract At the Department of Chemistry and Technology of Saccharides, Institute of Chemical Technology in Prague, we study technically important physical properties of sugar solutions. This paper deals with some results of measurement and correlation of boiling point elevation and density. The present system of tables or nomograms of physical properties of sugar solutions is not satisfactory for automated data processing. In a critical analysis of the existing material it appears that physico-chemical data for sugar solutions were often compiled over ranges of variables which were interesting for laboratory control and not for engineering computations. That all calls for purposeful completion of data in the regions where they are lacking. Additionally, it calls for revision of tabulated values from the literature and for transformation of the tabulated data to functional relationships in order to make computation equations both precise and simple