Optimization of modifed atmosphere packaging with respect to physicochemical characteristics of Requeijão

The e ects of modi®ed atmosphere packaging on physicochemical and sensorial characteristics (contents of free fatty acids, lac- tose, lactic acid and moisture, as well as pH and rigidity) in Portuguese whey cheese (RequeijaÄo) were studied following a response surface methodology using storage time, storage temperature and fraction of CO2 in the ¯ushing gas as manipulated variables. Inspection of the sensorial optima in terms of the di erent parameters indicated that it is convenient to set the storage temperature equal to 4 C because no signi®cant lipolysis takes place, irrespective of overhead atmosphere. Plain CO2 as ¯ushing gas will in general ensure more constant composition until 15 days and will provide protection against extensive lipolysis. In terms of overall visual aspect, all packaged cheeses were preferred to their unpackaged counterparts; however, in terms of acidic smell, only whey cheeses stored at 4 C exhibited signi®cant di erences relative to those stored at higher temperatures

Effect of thermal treatment on the protein profile of whey from ovine and caprine milk throughout lactation

The independent and combined effects of temperature, heating period and stirring rate on the extent of precipitation of each of the major proteins in ovine and caprine acid wheys at various stages of lactation were studied using two-level, replicated, complete factorial designs. Evaluation of the extent of precipitation was based on the quantitative results obtained by gel permeation chromatography. Statistical analyses indicated that temperature is the most important factor in the precipitation of u-lactalbumin and /I-lactoglobulin from acid whey from both ovine and caprine milks. The magnitude of the independent effects of heating time and stirring rate on the precipitation of B-lactoglobulin and a-lactalbumin from ovine whey reached local maxima as lactation elapsed, but such effects were rather small for caprine whey

On a zero speed sensitive cellular automaton

Using an unusual, yet natural invariant measure we show that there exists a sensitive cellular automaton whose perturbations propagate at asymptotically null speed for almost all configurations. More specifically, we prove that Lyapunov Exponents measuring pointwise or average linear speeds of the faster perturbations are equal to zero. We show that this implies the nullity of the measurable entropy. The measure m we consider gives the m-expansiveness property to the automaton. It is constructed with respect to a factor dynamical system based on simple "counter dynamics". As a counterpart, we prove that in the case of positively expansive automata, the perturbations move at positive linear speed over all the configurations

Influence of salt content, degree of proteolysis and aeration on the production of a polymer via fermentation of whey-related media by Rahnella aquatilis

Utilization of whey as fermentation feedstock has been attempted widely by the dairy industry. Production of lactan, a polysaccharide composed of mannose, galactose and galacturonic acid (at the molar ratio 5:3:2), starting from a semi-defined medium containing lactose via fermentation under aerobic conditions with Rahnella aquatilis was described previously. In this communication, the effect of salt, previous hydrolysis and aeration were studied during the polysaccharide production from whey in alternative fermentation media: hydrolyzed whey (under (i) aerobic and (ii) anaerobic conditions), hydrolyzed whey with 2.0% NaCl (w/v) (iii) and 0.5% NaCl (w/v) (iv),.and plain whey (v). The growth of biomass and the variation in concentration of organic acids, lactose, peptides and free amino acids were monitored. The polysaccharide production and the variation of viscosity of were also followed throughout 48 h of fermentation. Under the different conditions tested, Rahnella aquatillis showed a maximum specific growth rate of 0.61 h-1, 0.60 h-1, 0.61 h-1, 0.64 h-1, and 0.46 h-1 for hydrolyzed whey under aerobiosis and under anaerobiosis, hydrolyzed whey with 2.0% NaCl (w/v) and 0.5% NaCl, and plain whey, respectively; the final yields of the various organic acids were: 0.07, 0.18, 0.07, 0.04 and 0.05 (g/glactose) for acetic acid; 0.06, 0.07, 0.00, 0.04 and 0.02 (g/glactose) for lactic acid; 0.08, 0.09, 0.03, 0.04 and 0.04 (g/glactose) for formic acid; 0.01, 0.04, 0.01, 0.01 and 0.02 (g/glactose) for succinic acid; and 0.11, 0.09, 0.14, 0.19 and 0.00 (g/glactose) for acetoine. Lactose was almost completely depleted during the 48 h of fermentation for hydrolyzed whey; however, lactose was only partly consumed in plain whey (final yield of 0.48 g/glactose).Small peptides (< 2,000 Da) and most free amino acids were consumed by 24 h in hydrolyzed whey fermented under anaerobiosis and plain whey, but these peptides were present until the end of fermentation in the remaining media. R. aquatilis showed similar behavior in free amino acid consumption in hydrolyzed whey with NaCl and hydrolyzed whey fermented under aerobiosis. Plain whey yielded very low concentrations of free amino acids throughout the whole fermentation. The yield of polysaccharide was 0.56, 0.26, 0.39, 0.40 and 0.44 g/glactose for hydrolyzed whey fermented under aerobiosis and under anaerobiosis, hydrolyzed whey with 2.0% NaCl (w/v) and 0.5% NaCl, and plain whey, respectively.info:eu-repo/semantics/publishedVersio

Production of lactan using plain whey, whey permeate and synthetic medium as feedstock

Whey (or whey permeate), a by-product of cheese manufacture, has created a worldwide problem of waste disposal owing to its high biological oxygen demand. Production of lactan has been previously described based on a semidefined medium rich in lactose using Rahnella aquatilis. This research was aimed at obtaining lactan directly from whole whey without additional nutrients, as well as and whey permeate obtained after ultrafiltration, using a similar type of strain, and the fermentation process was compared with that using the synthetic medium previously tested. The growth of biomass growth rate, the polysaccharide production rate and the viscosity of the broth were monitored. Organic acids, lactose, peptides and free amino acids were also determined. The growth curves were similar for the three media, showing a maximum specific growth rate of 0.61 h1, 0.65 h-1 and 0.63 h-1 for whey, whey permeate and synthetic medium, respectively. The major increase in polysaccharide production was observed between 12 h (beginning of stationary phase) and 24 h for whey and the synthetic medium; however, the increase in the case of whey permeate is less pronounced and occurs essentially after 24 h. The yield of polysaccharide was 0.59 g/glactose, 0.56 g/glactose and 0.37 g/glactose for synthetic medium, plain whey and whey permeate, respectively. The larger amount of citrate present in whey was used by Rahnella aquatilis with significant formation of acetic acid in the first 12 h and acetoine thereafter; whey permeate and synthetic media did not lead to acetoine formation. The final yields of the various organic acids for the synthetic medium, whey and whey permeate, respectively, were: 0.08, 0.07 and 0.03 (g/glactose) for acetic acid; 0.02, 0.06 and 0,00 (g/glactose) for lactic acid; 0.08, 0.08 and 0.02 (g/glactose) for formic acid; 0.04, 0.01 and 0.00 (g/glactose) for succinic acid; and 0.00, 0.11 and 0.00 (g/glactose) for acetoine. Lactose was almost completely depleted by 48 h of fermentation in the case of whey and synthetic medium, but only part of lactose was consumed in the whey permeate (final yield of 0.43 g/glactose). Small peptides (< 4,000 Da) and most free amino acids were consumed by 24 h in whey and synthetic medium. The whey permeate possessed low amounts of peptides (virtually consumed by 12 h) and very low concentrations of free amino acids, which increased slightly between 12 and 24 h.info:eu-repo/semantics/publishedVersio

Controlled whey protein hydrolysis using two alternative proteases

Whole whey was hydrolyzed for 12 h with Protease 2A and Trypsin using two concentrations of enzyme (20 and 40 g/kgprotein). Samples were assayed for total viable counts of adventitious microflora that survived thermization, total acidity, total concentration of free amino acids, peptide profile and overall degree of hydrolysis. The highest total concentration of free amino acids was observed when hydrolysis was effected by Protease 2A, and the major variations in amino acid qualitative composition occurred between 2 and 6 h: Leu exhibited the most significant increase, followed by Lys, Phe and Ile. Hydrolysis with Trypsin led to release of high amounts of Lys. Quantitative depletion of β-lactoglobulin was observed by 2 h under all processing conditions, and hydrolysis of α-lactalbumin was slower when Trypsin was employed. Formation of peptides was more extensive under the action of Trypsin than of Protease 2A, and the major peptides released by the former had molecular weights mainly in the ranges 7500–8000 and 4000–4500 Da, whereas those released by the latter accumulated in the range 7000–7500 Da. The differences between the hydrolytic actions of Trypsin and Protease 2A were significant except with respect to the concentration of Glu, as well as degree of breakdown of immunoglobulin G and β-lactoglobulin. Growth of adventitious bacteria and generation of free amino acids were successfully modeled using postulated mathematical models. The values of vmax for Trypsin were 0.15 and 0.06 g/(l h) for 40 and 20 g/kgprotein, respectively, and for Protease 2A were 0.86 and 0.50 g/(l h) for 40 and 20 g/kgprotein, respectively

Spin, charge, and orbital correlations in the one-dimensional t2g-orbital Hubbard model

We present the zero-temperature phase diagram of the one-dimensional t2g-orbital Hubbard model, obtained using the density-matrix renormalization group and Lanczos techniques. Emphasis is given to the case for the electron density n=5 corresponding to five electrons per site, of relevance for some Co-based compounds. However, several other cases for electron densities between n=3 and 6 are also studied. At n=5, our results indicate a first-order transition between a paramagnetic (PM) insulator phase and a fully-polarized ferromagnetic (FM) state by tuning the Hund's coupling. The results also suggest a transition from the n=5 PM insulator phase to a metallic regime by changing the electron density, either via hole or electron doping. The behavior of the spin, charge, and orbital correlation functions in the FM and PM states are also described in the text and discussed. The robustness of these two states varying parameters suggests that they may be of relevance in more realistic higher dimensional systems as well.Comment: 9 pages, 8 figure