M.H. López-Leiva

Continuous production of oligosaccharides from whey using a membrane reactor

Abstract Whey permeate (containing 14, 20 or 23% lactose) was used in the continuous production of oligosaccharides (OS) by hydrolysis from Maxilact 2000 L ( Kluyveromyces lactis β- d -galacosidase). Two types of membrane reactors were used: a laboratory scale, Amicon stirred cell, using a flat membrane (41.8 cm 2 ) and a pilot plant-scale membrane reactor using a Romicon hollow fiber cartridge (0.5 m 2 ). Batch experiments were run to determine the optimal reaction time (when the largest amount of OS are produced). This optimal reaction time was then used in the experiments in continuous mode as the mean residence time of the whey permeate in the reactor, which could be controlled by adjusting the rate of permeate and or the volume of the substrate in the system.

Formation of oligosaccharides from whey UF-permeate by enzymatic hydrolysis : analysis of factors

Abstract Two-level fractional factorial experiments were designed to study effects of enzyme (0.05 and 0.1%) and initial lactose concentrations (Lo: 14 and 23%), pH (5.0 and 7.0) and temperature (35 and 45 °C) on enzymatic formation of oligosaccharides (OS) from whey UF-permeate in a batch reactor. β- d -galactosidase from Aspergillus oryzae (A), Kluyveromyces lactis (B) and K. fragilis (C) were compared. Hydrolysis with B and C gave comparable yields which were higher than that from A at identical conditions. Lo did not influence reaction time, but concentration of OS significantly increased by increasing Lo for all enzymes. Increasing Lo reduced the yield after hydrolysis with A and B, but improved the yield for C. Lo had negligible effect on degree of hydrolysis (DH) for A and C. However, increasing Lo significantly lowered DH for B. Increasing enzyme concentration significantly reduced reaction time for A, but it had no effect on that for B and C. DH significantly decreased after increasing concentration of A. Consequently, OS and yield were reduced. Applying B and C at higher concentration improved DH, OS and yield. Increasing temperature or pH reduced DH, OS and yield for A, but increased the responses for B and C.

Description of a rotating ultrafiltration module

Abstract In ordinary UF modules the ratio flux to hold-up volume and the demand for a minimum linear flow speed are such that recirculation is necessary in order to reach an interesting concentration ratio. In the suggested design a narrow slit is formed between two surfaces, one or both of which are covered by the membrane. One of the surfaces moves parallel to the other thus producing a shear rate. In this way the permeate flux is made independent of the circulation flow and the liquid may be treated in single pass flow at a high concentration ratio. In this apparatus liquids with higher viscosity than in stationary UF modules may be treated. The test apparatus will be described and preliminary results presented.

Ultrafiltration at low degrees of concentration polarization: technical possibilities.

Abstract The phenomenon of CP produces well known deleterious effects in UF, the most important being the many-fold diminishing of trans-membrane flux. Classical methods used to decrease this negative influence have made use of either a turbulent flow or a high shear stress laminar flow past the membrane. In both cases the liquid is recirculated through the UF-module until the desired degree of concentration is obtained. The same type of flow can be obtained either by moving the membrane in relation to the liquid or by moving a surface parallel to the membrane. Here the velocity of the fluid across the module is irrelevant and consequently it can be set according to the degree of concentration required. In this paper two modules working with this principle will be presented. One of laboratory-scale size is composed of a pair of concentric cylinders of which the innerone, carrying the semi-permeable membrane, is rotatable. The other module, of around 0.6 m2 membrane area, is of the “rotary plate-and-frame” type. Energy consumption curves for each module as well as their performance in the ultrafiltration of BSA solutions and milk will be presented.

The original Plank equation and its use in the development of food freezing rate predictions.

Abstract A large number of methods to predict freezing and thawing times for foodstuffs have been proposed. Normally the original Plank equation is used as the starting point, but since this equation does not include the times below and above the freezing itself, several attempts have been made to improve it by adding new terms and parameters, to make it suitable for the entire freezing process. In this paper, Plank’s equation and how it has been interpreted and modified by different scientists during the years is reviewed and discussed. We assess as well several of these models, by comparing the values they predict with experimental freezing times available for the same experimental conditions. Two software programs are also included in the analyses: a commercial package and an own developed software which follows the entire freezing process by a simple geometrical iterative approach.

A study of factors affecting extraction of peanut (Arachis hypogaea L.) solids with water

Abstract The effects of pH, temperature, time, solids-to-water ratio, speed of agitation, partial hydrolysis of proteins, and soaking on the extraction of peanut ( Arachis hypogaea L.) solids with water were studied using a fractional factorial set of experiments. Temperature, pH, solids-to-water ratio, hydrolysis, and soaking were significant for protein extraction. Temperature, speed of agitation, hydrolysis, and soaking were significant for fat extraction. Only hydrolysis and soaking were significant for carbohydrate extraction. Protein recovery was increased when hydrolyzed. Increased pH and solids-to-water ratio also increased protein recovery. Fat recovery was greatest at high agitation speed. Soaking highly increased carbohydrate contents of extracts, and decreased protein and fat. Hydrolysis was found to depend on temperature and time.

Nutritional, sensory and physicochemical properties of peanut beverage sterilized under two different UHT conditions

Abstract Chocolate-flavoured peanut beverage was UHT-sterilized at 137 °C for 4 s (C04) or 20 s (C20) and aseptically filled in Tetra brik cartons. Microbiological, physico-chemical, sensory and nutritional properties of the beverages were evaluated. No bacterial cells, spores, yeasts or moulds were observed. The power law described the rheological behaviour (k = 0.28, n = 0.53). Stability of C04 and C20 was high as indicated by the low homogenization (0%) and sedimentation (0.15 and 0.20 ml 12 ml ) indices. C20 was darker and less viscous than C04. The sensory and nutritional properties of C20 did not significantly differ from those of C04. Aroma and taste mean scores were ( 4.2 5 ) and ( 3.8 5 ), respectively, and correlated with acceptability ( 5.4 7 ). Bitterness was not perceived in any sample. C04 contained (g/100 g beverage) protein (3.0), fat (5.2) and carbohydrates (9.6). It also contained (mg/100 g beverage) thiamin (0.3), vitamin E (0.7), niacin (1.4), iron (0.5), copper (0.2), manganese (0.2), vitamin A (3.6 μg RE), riboflavin (0.01), vitamin C (0.4) and calcium (5.5). The contents of essential amino acids were (mg/g protein) cystine + methionine (17), histidine (17), isoleucine (30), leucine (67), lysine (26), threonine (20), tryptophan (13), tyrosine + phenylalanine (69) and valine (35). The in vitro protein digestibility was 75%, and the protein digestibility corrected amino acid score (PDCAAS) was 34%.

Effect of pH and heat treatment on the mutagenic activity of peanut beverage contaminated with aflatoxin B1

The effect of pH and heat treatment on the mutagenic activity (assayed by Ames test) of peanut beverage contaminated with aflatoxin B1 (15, 30 and 45 μg/kg) was studied. Heating the beverage at 130°C for 20 s, 140°C for 5 s and 121°C for 15 min at pH 8.0 did not significantly (p < 0.001) reduce the mutagenic activity. Heating the beverage at 130°C for 20 s and 121°C for 15 min at pH 10.2, however, reduced the mutagenic activity by 73.3–83.0% (79.4 ± 5.3%) and 82.5–92.5% (86.6 ± 5.2%) respectively. Also heating the beverage at 130°C for 20 s and 121°C for 15 min at pH 5.0 reduced the mutagenic activity by 72.5–80.4% (75.2 ± 4.5%) and 70.4–74.7% (71.9 ± 2.4%) respectively. Changing the pH of the beverage from 8.0 to 10.2 or 5.0, without heating, did not significantly (p < 0.001) reduce the mutagenic activity.

Prediction of Permeate Fluxes in UF/RO Systems

A membrane plant (Ultrafiltration or Reverse Osmosis) can be operated in one of two ways: batch or continuous. The continuous arrangement in its turn can be with partial recirculation (recirculating system), or without recirculation at all (single-pass). In fig. 1 an UF/RO circuit has been sketched. Depending on the value of the ratio R/C(= recirculation flow/final product flow) this circuit can represent each of the three basic arrangements seen: When R/C = ∞ (C=0), all the retentate is recirculated and the circuit corresponds to a batch system. In the other extreme when R/C = 0 (R=0), we have the case of a single pass-system. A value of R/C between these two boundaries represents a continuous system with partial recirculation.