I. Panchev

On the production of low esterified pectins by acid maceration of pectic raw materials with ultrasound treatment

Abstract The effect of temperature, time and nitric acid concentration on the yield and quality of low esterified pectins obtained from apple pressings by preliminary acid maceration of the raw materials was studied. Regression equations describing the changes in the degree of esterification, the yield, the polyuronide content and the characteristic viscosity of the pectins obtained depending on the temperature and time of maceration of apple pressings at various nitric acid concentrations were derived. The opportunity of intensifying the process of pectin deesterification by combining the acid maceration of raw materials with ultrasound treatment was investigated. An additional decrease in the degree of esterification of pectin (about 6%) and an important increase in the yield of pectin (about 18%), as compared to the reference sample, were established. The optimum ultrasound treatment proved to be within 24–30 min. A more prolonged ultrasound treatment resulted in obtaining pectins of lower gel strength.

Extraction of pectin from fruit materials pretreated in an electromagnetic field of super-high frequency

Abstract Laboratory studies on the extraction of pectin from orange, lemon and apple wastes pretreated in an electromagnetic field of super-high frequency were carried out. A 10-min preliminary microwave heating (2450 MHz, 0·5 kW) of crushed fruit materials was found to provide a higher pectin yield. The extracted pectin exhibited higher values for degree of esterification and gel strength compared with the control sample. The effect depends on the kind of raw material. The favourable effect of microwave heating on the yield and quality of pectin is assumed to be due first to the partial disintegration of the plant tissue and hydrolysis of protopectin, and second, to the rapid inactivation of the pectolytic enzymes in the raw material. The second hypothesis has been partly confirmed by model experiments. The results presented can serve as a basis for improving pectin manufacturing. It is expedient that fresh pectinous raw materials should be subjected to microwave heating before drying.

Optimization of Rosmarinic Acid Production by Lavandula vera MM Plant Cell Suspension in a Laboratory Bioreactor

The all‐round effect of dissolved oxygen concentration, agitation speed, and temperature on the rosmarinic acid production by Lavandula veraMM cell suspension was studied in a 3‐L laboratory bioreactor by means of the modified Simplex method. Polynomial regression models were elaborated for description of the process of rosmarinic acid production (Y) in the bioreactor as a consequence of the variation of the dissolved oxygen (X1) concentration between 10% and 50%; agitation (X2) between 100 and 400 rpm; and temperature (X3) between 22 and 30 °C. The optimization made it possible to establish the optimal conditions for the biosynthesis of rosmarinic acid by L. veraMM: dissolved oxygen (X1*), 50% of air saturation; agitation (X2*), 400 rpm; and temperature (X3*), 29.9 °C, where maximal yield (Ymax) of 3489.4 mg/L of rosmarinic acid was achieved (2 times higher compared with the shake‐flasks cultivation).

Comparative study of texture of normal and energy reduced sponge cakes

The complete sucrose elimination and its replacement by microencapsulated aspartame (Nutra Sweet) and bulking agents (sorbitol, wheat starch and wheat germ) on the physical and textural sensory characteristics of two diabetic sponge cakes against a control sponge cake was studied. Mathematical and statistical methods were used and regression models worked out, describing the physical and textural characteristics of the three sponge cakes and their values were optimized. The effect on the porosity, springiness, volume and shrinkage of sponge takes was substantial and depended on the amount of the added ingredients. The diabetic sponge cake containing wheat germ showed the least physical and sensory deviations against the control sponge cake. The energy value of the diabetic sponge cakes against the control one was reduced with 25% for the ordinary sponge cake without sucrose and with 29% for sponge cake without sucrose containing wheat germ.

Nutrient Medium Optimization for Rosmarinic Acid Production by Lavandula vera MM Cell Suspension

The overall effect of NH4NO3, KNO3, and KH2PO4 on the biosynthesis of rosmarinic acid and cell biomass by Lavandula vera MM cell suspension was studied by the method of the full factor experiment. Polynomial regression models were elaborated to give a quantitative description of the processes of biosynthesis of rosmarinic acid (Y1) and cell biomass (Y2) as a result of the variation of the concentration of NH4+, 0.09 g/L ≤ X1 ≤ 0.23 g/L; NO3‐, 2.44 g/L ≤ X2 ≤ 3.02 g/L; and KH2PO4, 0.170 ≤ X3 ≤ 0.425 g/L. Optimization procedures according to the modified Simplex method allowed us to establish the optimal conditions for the biosynthesis of rosmarinic acid by Lavandula vera MM: X1* = 0.09 g/L; X2* = 3.02 g/L, and X3* = 0.170 g/L, where Y1*max = 1786.74 mg/L (27 times higher compared with the cultivation in the standard Linsmayer‐Skoog medium). As a result, modified ingredients of the Linsmayer‐Skoog nutrient medium were applied for the cultivation of Lavandula vera MM to achieve a maximum yield of rosmarinic acid.

Emulsifying power of mannan and glucomannan produced by yeasts

Subject of study was the colloid chemical properties of the biopolymers mannan, synthesized from strain Rhodotorula acheniorum MC, and glucomannan, synthesized from strain Sporobolomyces salmonicolor AL1. Their emulsifying capacity was studied in model systems of aqueous solutions in concentrations from 0.5% to 2.5% with regard to the aqueous phase. Emulsions of the direct type (oil/water) with 50% oil content were obtained. A disperse system with 2.5% glucomannan had 100% intact emulsion in the centrifugation test, while for the system with mannan, this indicator was 72%. Lab cream emulsions were obtained with glucomannan and with the emulsifiers Rofetan N/NS and Arlacel 165 used in the cosmetics industry. It has been established that under standard testing conditions, cream‐like emulsions with 2.0% glucomannan have stability indicators comparable to these of 5.0% rofetan N/NS and 5.0% Arlacel 165. The samples with different concentrations of glucomannan showed a pseudo‐plastic behaviour, as the highest viscosity was shown by the emulsion with 2.0% stored at 45°C. The newly synthesized exopolysaccharides had a distinct emulsifying power and can be applied in the cosmetic and food industries.

Kinetic model of pectin extraction

Abstract A model describing the kinetics of pectin extraction is presented. The effect of degradation on the yield of pectin has been taken into account. It is applied to extraction experiments with apple pressings and 0·5% nitric acid at temperatures of 60°C, 70°C and 80°C in laboratory extraction equipment. The suggested theoretical model provides an opportunity to predict the yield of pectin, the quantity of depolymerized pectic substances and the optimum duration of extraction.

L-ascorbic acid in nonenzymatic reactions. I: Reaction with glycine

ZusammensetzungEs wurde der Einfluß des Wassergehalts, des Molverhältnisses, der Zeit und der Temperatur auf die Bildung nicht dialysierbarer Melanoidine im Modellsysteml-Ascorbinsäure-Glycin erforscht. Die isolierten Melanoidine sind durch UV- und IR-Spektren charakterisiert und durch Gelchromatographie fraktioniert. Berechnet sind die Reaktionsgeschwindigkeitskonstanten für Temperaturen von 90°, 100° und 110°C, welche (0.84±0.29) x 10−5 x s−1, (1.33±0.14) x 10−5 x s−1 und entsprechend (5.30±0.37) x 10−5 x s−1 sind. Die Aktivierungsenergie der Reaktion wurde zu 106.07±32.47 kJ/ mol bestimmt.AbstractThe influence of the water content, molar ratio, time and temperature on the formation of nondialysable melanoidins produced by the interaction ofl-ascorbic acid and glycine has been studied. The isolated polymers have been characterized by spectrum analysis and fractionated using gel chromatography. The rate constants of the reaction for temperatures of 90°C, 100°C and 110°C have been calculated and are (0.84±0.29) x 10−5 x s−1, (1.33±0.14) x 10−5 x s−1 and (5.30±0.37) x 10−5 x s−1 respectively. The activation energy of the reaction has been determined to be 106.07±32.47 kJ/mol.

Influence of microwave pretreatment of fresh orange peels on pectin extraction

Abstract Laboratory studies on the extraction of pectin from orange peels, pretreated in an electromagnetic field of hyper frequency, were carried out. The influence of intensity of microwave treatment (P w ) and time on pectin yield and pectin quality was investigated. It was established that the increase of P w and time lead to increase in the pectin yield with 180–240% in comparison with the control. Apparently, the microwave treatment leads to a considerable increase in the soluble form of pectin, characterized by increase in the jelly strenght and in the polyuronic content.

On the molecular weight of pectic substances and its relation to their gel strengths

Abstract A study has been made on the possibility of determining the molecular weight M w , the second virial coefficient A 2 and the radius of gyration by measuring the light scattering of pectin aqueous solutions. The experimental data were processed on a computer by using an algorithm, accounting for the effect of microgel formations in the pectic solution. A tendency towards a decrease in M w when decreasing the degree of esterification for a certain type of pectin was established and was confirmed by the change in the intrinsic viscosity [η]. This fact is explained by degradation during deesterification. The dependence of the gel strength of the pectic preparations on their degree of esterification, molecular weight M w and purity (p%) was also studied as well as the dependence of the gel strength on the intrinsic viscosity [η], the degree of esterification and the purity p%. The passive multifactor experiment method was used to obtain regression models which were tested for an optimum in the factors influencing the gel strength. The optimal value for the degree of esterification was obtained at 57–58% which confirmed the view that within this range the pectin macromolecules possess maximum conformational flexibility.