Marek Sady

Rheological Properties and Texture of Yoghurts When Oat-Maltodextrin is Used as a Fat Substitute

Yoghurts were produced from cow’s milk containing 1, 2 and 3 kg milk fat/100 kg or 1, 2 and 3kg of oat-maltodextrin/100 kg (maltodextrin included 5 kg β-glucan/100 kg). Non-fat yoghurt, without the addition of maltodextrin, was used as a control product. The yoghurts were estimated for sensory properties and using instrumental texture profile analysis (TPA) and rheological investigations, which had to set flow curves and their description by the Ostwald de Waele and Casson models; counting apparent viscosity were also done. Replacing milk fat with maltodextrin in yoghurts does not show significant differences in the sensory analysis, rheological properties and most of the texture parameters. The addition of milk fat in the amount of 1 kg/100 kg or maltodextrin in 2 kg/100 kg caused an increase in apparent viscosity of yoghurts. The addition of oat-maltodextrin caused a decrease in consistency index value and a deviation from the Newtonian flow and yield stress, similar to the effects caused by adding milk fat. No relationship between the results of the sensory evaluation, the instrumental texture parameters and rheological properties, especially in yoghurts containing milk fat, were shown

The Influence of Storage Time on Rheological Properties and Texture of Yoghurts with the Addition of Oat-Maltodextrin as the Fat Substitute

Yoghurts from cows milk containing 2 kg milk fat/100 kg or 2 kg of an oat-maltodextrin/100 kg (maltodextrin included 5 kg b-glucan/100 kg), were weighed on a laboratory scale and stored in refrigerator conditions for 21 days. Non-fat yoghurt without the addition of maltodextrin was used as a control product. The yoghurts were analysed after 1, 7, 14, and 21 days of storage. Sensory evaluation, instrumental texture profile analysis, and rheological investigations were carried out. They included the determination of the flow curves and the description by Ostwald de Waele and Casson models as well as an account of the apparent viscosity. Differences in the sensory quality of yoghurts containing milk fat or maltodextrin were not found, whereas these yoghurts were characterized by better sensory quality than the control product. The storage time had a significant influence on the sensory evaluation and the texture parameters. During the storage time, the apparent viscosity of yoghurts decreased. A decrease in consistency index value, in deviation from Newtonian flow, and yield stress was noticed, whereas in Cassons viscosity of the yoghurts, an increase was found.

Biodegradable Complex Polymers from Casein and Potato Starch

Potato starch was blended with defatted milk in proportions providing a 4:1, 3:1, 2:1, 1:1, 1,:2, 1:3, and 1:4 starch/casein ratio. Precipitation was achieved by addition of either hydrochloric acid or leaven. Composition of precipitated products was determined based on elemental analysis for nitrogen. Generally, differences between attempted and achieved casein-to-starch proportions did not exceed 10%. Products coprecipitated with hydrochloric acid were slightly richer in casein than products obtained with leaven. Aqueous solubility, water binding capacity, IR spectra, and thermal analysis (thermogravimetry, TG, and differential thermogravimetry, DTG) were recorded for the precipitates. Analyses revealed that the precipitates were not simple physical mixtures of the components. Partial insolubility in 7 M aqueous urea showed that casein and potato starch are chemically bound. Comparison of the spectra and thermograms suggested that complexes of the 1:1 composition were formed constituting a nucleus of the aggregates carrying excessive amounts of either starch or casein.

Hydrocolloids in Forming Properties of Cocoa Syrups

Abstract Agar, carrageenan, carboxymethylcellulose (CMC), and xanthan gum at diversified concentrations were used in coca syrup as stabilizer, thickener, and consistency providers. The syrups obtained in the laboratory conditions were compared to the commercial ones. Sensory evaluation of both commercial and laboratory syrups was comparable, however, the latter obtained slightly higher appraisal. Based on the texture profile analyses (TPA), it was concluded that laboratory and commercial syrups had similar textural properties with one exception. Value of stringiness of laboratory syrups was lower. This factor gave an advantage in evaluation of suitability of these products for consumers, who considered it as more comfortable in use. Rheological properties of syrups were compared by the use of Cassons model. Commercial syrups had yield stress (τ o ) in the range of 0.38–3.74 Pa, and Cassons viscosity in the range of 0.50–3.84 Pa s. Laboratory syrups had more diversified rheological properties. It was also concluded that all selected hydrocolloids (CMC, carrageenan, xanthan gum, and agar) were useful, however to different extent, for cocoa syrups production.

Estimation of the antioxidant activity of the commercially available fermented milks

BACKGROUND Free radicals are connected with the increased risk of certain diseases, especially cancers. There is some scientific evidence that antioxidant-rich diet may inhibit the negative impact of free radicals. The aim of the present study was to analyse the antioxidant capacity of the selected commercial natural and flavoured fermented milks offered in Poland, derived from different producers. METHODS The following commercially available natural fermented milks: 12 yoghurts, 12 kefirs, 2 butter milks, 2 cultured milks, Turkish yoghurt drink (ayran) and the following flavoured fermented milks: 22 yoghurts, 2 acidophillus milks, 2 kefirs, butter milk and vegetable flavoured fermented milk were analysed for their antioxidant potential. The antioxidant capacity was assessed, in two replicates and twice for each product, by means of ferric reducing antioxidant power (FRAP) and DPPH radical scavenging ability (expressed as ARP - anti radical power) methods. RESULTS Among all analysed plain products, yoghurts and kefirs were characterised by the highest antioxidant activity. The presence of probiotic Lactobacillus casei strains in the product positively affected both FRAP and ARP values. Antioxidant capacity of the flavoured fermented milks was primarily affected by the type and quality (e.g. fruit concentration) of the added flavouring preparation. The most valuable regarding the estimated parameters were chocolate, coffee, grapefruit with green tea extract as well as bilberry, forest fruits, strawberry and cherry with blackcurrant fillings. CONCLUSIONS Protein content, inclusion of probiotic microflora as well as type and quality of flavouring preparations are the main factors affecting antioxidant properties of fermented milks.

Polymeric Complexes of Cornstarch and Waxy Cornstarch Phosphates with Milk Casein and Their Performance as Biodegradable Materials

Complexes of phosphated cornstarch and waxy cornstarch with casein were prepared and characterised. They were prepared from casein in defatted milk and corn and waxy corn starches phosphated to degree of substitution values (DS) of 0.0637 and 0.0968, respectively. The components were blended in starch to casein ratios of 2:1, 1:1, and 1:2, then precipitated with hydrochloric acid. Aqueous solubility, water binding capacity, IR spectra, and thermal analysis (thermogravimetry, TG, and differential thermogravimetry, DTG) of the precipitates revealed that they were not simple physical mixtures of the components. The components interact with one another electrostatically with involvement of the starch phosphate groups and the peptide bonds of casein as documented by the IR spectra. Because of their insolubility in 7 M aqueous urea solution they might also be considered as complexes in which the components were chemically bound. Enzymatic studies showed that they are biodegradable materials.

The influence of texture improver type and its addition level on rheological properties of goat’s milk yogurt

Set yoghurt from goat’s milk with addition of two texture improvers DSE 6693 and DSE 6694 from NZMP New Zealand, added in the amount of 1, 2and 3% and control yogurt without addition of texture improvers were produced. In yogurt determined sensory quality, pH, apparent viscosity and rheological properties. Flow curves obtained for produced yogurts were described by three rheological models: Ostwald de Waele, Herschel-Bulkley (H-B) and Casson. Addition of texture improver caused an increase in total solids and total protein content of milk for yogurt. Yogurt with texture improvers gave better sensory quality than control yogurt. The yogurt with 1% addition of DSE 6693 and with 2% addition of DSE 6694 had the best sensory quality. The increase in addition level of texture improvers caused an increase in apparent viscosity, consistency coefficient K, yield stress (except H-B model) and deviation from Newtonian flow (decrease of flow index n). Effect of type of improver was rather negligible, whereas its level addition considerably influenced the evaluated rheological parameters.

The suitability of different probiotic strains for the production of fruit-whey beverages

BACKGROUND When designing new probiotic products, one of the most important aspects is the selection of bacterial strains with high survival rates in the matrix of the product concerned. The aim of the present research was to evaluate the potential of selected strains of probiotic bacteria for the production of fruit-whey beverages. METHODS Orange, apple and blackcurrant whey beverages were produced, and each was inoculated with one of the following probiotic strains: Bifidobacterium lactis HN019TM; Lactobacillus aci- dophilus NCFM®; Lactobacillus paracasei Lpc-37TM; Lactobacillus rhamnosus HN001TM. The count of probiotic bacteria as well as pH and total acidity were evaluated at the 1st, 7th, 14th, 21st and 28th day of storage. RESULTS Beverages containing L. paracasei Lpc-37TM or L. rhamnosus HN001TM were characterized by a sig- nificantly higher average number of viable cells (7.02 or 7.05 log cfu/g, respectively) than products with lactis HN019TM or L. acidophilus NCFM® (6.43 or 6.37 log cfu/g, respectively). The use of L. paracasei Lpc-37 and L. rhamnosus HN001 strains in orange and apple drinks allows the recommended count for probiotic products, 106 cfu/g for 28 days of storage, to be exceeded. Survival of the B. lactis HN019 strain fulfills the above requirements only in the orange drink. The L. acidophilus NCFM® strain was found to be the least suitable for the production of beverages, as it did not reach 6 log cfu/g in any products after 28 days of stor- age. The highest average number of bacteria was found in the orange beverages (7.14 log cfu/g). In terms of bacteria viability, blackcurrant juice was the least suitable for the production of whey probiotic drinks, due to its high acidity. CONCLUSIONS The results of the present study indicate that careful selection of the fruit juice component, especially in terms of its acidity, is key to designing successful probiotic fruit-whey beverages. Other factors which should be taken into account to ensure a sufficient number of live probiotic cells, i.e. their therapeutic level in fruit-whey drinks, are the choice of probiotic strain and determination of the maximal shelf life.