Modeling of Calcium Chloride and Pectin Methylesterase Prefreezing Treatments of Strawberries and Jams

ABSTRACT: :
Different calcium chloride (CaCl₂) and pectin methylesterase (PME) prefreezing treatments in a vacuum were used to clarify the most effective prefreezing factors for strawberries and traditional jams. Fractional factorial design and modeling were used. CaCl₂ had the greatest effect on the majority of the 15 studied responses ( p < 0.001). The pretreatment time should be short (about 5 to 10 min), the temperature low (less than 20 °C), the vacuum level high (pressure less than 10 kPa), the CaCl₂ concentration moderate (about 1%) and the dosage of PME comparatively low (about 50 to 100 nkat/g) in order to yield high quality frozen strawberries for jam making.     

Extrusion-cooking of wheat flour-carrot mixture

Wheat flour with carrot pulp at different concentrations was extrusion-cooked in a twin-screw extrusion-cooker with varied screw rotation speed, mass temperature in the extruder barrel and feed moisture content. In addition to chemical analyses to determine the concentrations of different sugars, the total specific energy consumption, the die pressure, the expansion ratios and the colour of the extrudates were measured. The results show that carrot contents of up to 16% in dry wheat flour can be used without losing the typical texture of expanded products.     

Transesterification of phospholipids in different reaction conditions

Transesterification of synthetic dimyristoyl phosphatidylcholine with oleic acid by commercial lipase preparations fromAspergillus niger andRhizomucor miehei was studied in the presence and absence of solvent. A high-performance liquid chromatography method for determination of the modified phosphatidylcholine was developed. Under solvent-free conditions, transesterification could be carried out as efficiently as in toluene, and the degree of hydrolysis was lower than in toluene. Transesterification was influenced by the water content as well as by the fatty acid concentration in the reaction mixture. The optimum water content for transesterification in solvent-free reaction medium was higher than in toluene with both lipases. The yield of modified phosphatidylcholine increased, and the degree of hydrolysis decreased with increasing fatty acid concentration. The maximum yield of modified phospha-tidylcholine, 35% of the original phospholipid, was obtained withR. miehei lipase.     

The potential of enzymatic peeling of vegetables

Epiderms of potatoes (Solanum tuberosum cv Asterix), carrots (Daucus carota L), Swedish turnips (Brassica napus L) and onions (Allium cepa L) were isolated and their structure was studied by bright‐field and epifluorescence microscopy as well as by chemical analyses. The suitability of commercial cellulase and pectinase preparations for the hydrolysis of isolated peels and whole vegetables was investigated. The enzymatic pretreatment significantly enhanced the degradation of peels of carrots and onions, whereas the hydrolysis of potato and Swedish turnip peels was very limited owing to the high cutin/suberin content on the vegetable surface. Copyright © 2003 Society of Chemical Industry     

Effects of Calcium Chloride-based Prefreezing Treatments on the Quality Factors of Strawberry Jams

ABSTRACT: Vitamin C contents of pretreated strawberries did not change during 2 mo of freezing, but after jam cooking and storage, the vitamin C contents of all the studied jams decreased dramatically. Jams made from strawberries treated with CaCl₂ and PME in a vacuum had the highest firmness compared to the reference or other pretreated jam strawberries (p < 0.05). According to sensory evaluation of the jams, different prefreezing treatments were shown to have a significant influence on the sensory attributes evaluated (p < 0.001), the only exception being the redness of color after 4 mo storage.     

Effect of enzyme‐aided pressing on anthocyanin yield and profiles in bilberry and blackcurrant juices

Bilberries (Vaccinium myrtillus) and blackcurrants (Ribes nigrum) were treated with extensive dosages of commercial cell wall degrading enzyme preparations, i.e. Econase CE, Pectinex Ultra SP‐L, Pectinex Smash, Pectinex BE 3‐L and Biopectinase CCM. The enzymes were dosed based on the polygalacturonase activity. The juice yield was improved in both berries as a result of the enzymatic treatment. The improvement was more pronounced with blackcurrants owing to their thicker cell walls. The impact of the enzymatic treatment on anthocyanins present in the juices was investigated using HPLC‐DAD. The enzyme preparations affected the contents and composition of anthocyanins in the juices. Pectinex Ultra SP‐L, Pectinex Smash, Pectinex BE 3‐L and Biopectinase CCM increased the total content of anthocyanins by 13–41% in the bilberry juices and by 18–29% in the blackcurrant juices. Econase CE, however, produced a dramatic decrease in the total anthocyanin content in the bilberry juice due to its enzyme profile, whereas no such effect was observed with the blackcurrant juice. All the enzyme mixtures tested produced a total or extensive loss of anthocyanidin galactosides in bilberry juice. Commercial enzyme preparations used in the production of berry juices can improve extraction of anthocyanins into the juice. However, they may effectively hydrolyse certain glycosides and thus affect the profile of extracted anthocyanins. Copyright © 2005 Society of Chemical Industry     

Transesterification of soy lecithin by lipase and phospholipase

Soy lecithin was modified by enzymatic transesterification in a solvent-free system. 1,3-SpecificRhizomucor miehei lipase was found to be efficient in the transesterification with lauric acid and oleic acid, where oleic acid was more incorporated into soy lecithin. Phospholipase A₂ incorporated lauric acid hardly at all, but it hydrolyzed lecithin efficiently. The mixture of lipase and phospholipase A₂ (1:1, w/w) incorporated lauric acid to the same extent as did 1,3-specific lipase alone at the same total enzyme concentration. The main fatty acids replaced were palmitic and linoleic acids by 1,3-specific lipase and its mixture with phospholipase A₂, and linoleic and linolenic acids by phospholipase A₂ alone, suggesting an improved oxidative stability of the resulting product. Hydrolysis could not be prevented, but it could be regulated by incubation time and by enzyme dosage. The minimal water content for significant incorporation of lauric acid into lecithin was below 0.5% of the weight of the reaction mixture.     

Enzymatic hydrolysis of oat and soya lecithin: Effects on functional properties

Enzymatic hydrolysis of oat and soy lecithins and its effects on the functional properties of lecithins were investigated. The phospholipase used was most efficient at low enzyme and substrate concentrations. More fatty acids were released from soy lecithin than from oat lecithin. The maximum degree of hydrolysis was 760 μmol free fatty acids per gram soy lecithin and 170 μmol free fatty acids per gram oat lecithin. On the basis of the total carbohydrate and phosphorus contents in the polar fractions of the lecithins, oat lecithin contained more glycolipids and less phospholipids than soy lecithin. With regard to functional properties, the stability of oil-in-water emulsions was enhanced by hydrolyzed soy lecithin and by crude and hydrolyzed oat lecithins, but only hydrolyzed soy lecithin prevented the recrystallization of barley starch. The dissociation enthalpy of amylose-lipid-complex (AML-complex) was significantly higher when hydrolyzed soy lecithin was present. Hydrolyzed oat lecithin slightly affected the dissociation enthalpy of AML-complex. The other lecithins had no effect on recrystallization or dissociation enthalpies in the barley-starch matrix.