Survival of probiotics encapsulated in chitosan-coated alginate beads in yoghurt from UHT- and conventionally treated milk during storage

Survival of the microencapsulated probiotics, Lactobacillus acidophilus 547, Bifidobacterium bifidum ATCC 1994, and Lactobacillus casei 01, in stirred yoghurt from UHT- and conventionally treated milk during low temperature storage was investigated. The probiotic cells both as free cells and microencapsulated cells (in alginate beads coated with chitosan) were added into 20 g/100 g total solids stirred yoghurt from UHT-treated milk and 16 g/100 g total solids yoghurt from conventionally treated milk after 3.5 h of fermentation. The products were kept at 4 degrees C for 4 weeks. The survival of encapsulated probiotic bacteria was higher than free cells by approximately 1 log cycle. The number of probiotic bacteria was maintained above the recommended therapeutic minimum (10(7) cfu g(-1)) throughout the storage except for R bifidum. The viabilities of probiotic bacteria in yoghurts from both UHT- and conventionally treated milks were not significantly (P > 0.05) different. (c) 2004 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.

Antibiotic residues in Brazilian UHT milk: a screening study

The aim of this research was to carry out a screening study to check the incidence of antimicrobial residues in Brazilian UHT milk according to rapid yoghurt method. Of the 100 (100%) samples analysed, 96 (96%) showed no traces of antibiotic residues while 4 (4%) indicated probable presence of antibiotic residues. The results suggest that the Brazilian Sanitary Surveillance Agency should apply continuous monitoring programs in order to obtain a safe product offering no health risks to consumers.

Increased CLA content in organic milk fermented by bifidobacteria or yoghurt cultures

This study investigates the kinetics of acidification, fatty acid (FA) profile and conjugated linoleic acid (CLA, C18:2 c9, t11) content in fermented milks prepared from organic and conventional milk. Fermented milks were manufactured with five mixed cultures: four different strains of Bifidobacterium animalis subsp. lactis (BL04, B94, BB12 and HN019) and Lactobacillus delbrueckii subsp. bulgaricus LB340, in co-culture with Streptococcus thermophilus TA040. The composition of milk was evaluated, and the kinetics of acidification was followed by continuous pH measurement using the Cinac system. The profile of FA, including CLA, was analyzed by gas chromatography. The chemical composition of conventional and organic milk was similar, with the exception of protein and Fe, the concentrations of which were higher in the organic milk. The rate of acidification was significantly influenced by the type of milk and the bacterial strain used. Co-cultures St-HN019 and St-BB12 showed higher maximal acidification rates in both milks. Final counts of S. thermophilus (9.0-10.1 log(10) colony forming units (CFU) . mL(-1), L)actobacillus bulgaricus (8.2-8.5 log(10) CFU . mL(-1)) and B. animalis subsp. lactis strains (8.3-9.3 log(10) CFU . mL(-1)) did not differ significantly in either milk. Unexpectedly, all fermented organic milks contained significantly higher amounts of CLA than the same milk before fermentation, whereas CLA amounts did not change during fermentation of conventional milk. Regardless of the type of milk, CLA was found to be significantly positively correlated with trans-vaccenic acid and negatively correlated with linoleic acid. Moreover, the CLA contents were significantly higher in fermented milks showing shorter fermentation times.

Microbiological quality of yoghurt commercialized in Vicosa, Minas Gerais, Brazil

Yoghurt consumption has been increasing since 1980 decade due to the search for healthy foods by consumers, including Brazil. In order to evaluate the quality of the yoghurt commercialized in Vicosa, Minas Gerais, Brazil, 36 samples were collected from markets and analyzed for coliforms (total and thermotolerant) and lactic acid bacteria (LAB) enumeration and pH, considering different times for expiration. Coliforms were not detected at levels higher than 0.3 MPN/g, and only 7 (19.4%) samples showed LAB counts lower than 10(7) CFU/g. However, the mean pH observed in these samples (4.4) was not significantly different when compared to samples with higher LAB counts, suggesting addition of weak starter cultures during the processing. In the samples with less than 15 days for expiration the LAB counts and pH values were 7.4 log CFU/g and 4.1, respectively, and they were lower when compared to samples with more than 16 days of commercial viability, but without significant differences. The obtained results indicate adequate quality of yoghurt commercialized in Vicosa.

The viability of three probiotic organisms grown with yoghurt starter cultures during storage for 21 days at 4 degrees C

This study investigated the viability of probiotic (Lactobacillus acidophilus LA5, Lactobacillus rhamnosus LBA and Bifidobacterium animalis subsp. lactis BL-04) in milk fermented with Lactobacillus delbrueckii subsp. bulgaricus LB340 and Streptococcus thermophilus TAO (yoghurt - Y). Each probiotic strain was grown separately in co-culture with Y and in blends of different combinations. Blends affected fermentation time(s), pH and firmness during storage at 4 degrees C. The product made with Y plus B. animalis subsp. lactis and L. rhamnosus had counts of viable cells at the end of shelf life that met the minimum required to achieve probiotic effect. However, L. acidophilus and L. delbrueckii subsp. bulgaricus were inhibited.

Viability of Lactobacillus acidophilus La-5 added solely or in co-culture with a yoghurt starter culture and implications on physico-chemical and related properties of Minas fresh cheese during storage

The effect of a probiotic culture of Lactobacillus acidophilus (La-5), added solely or in co-culture with a starter culture of Streptococcus thermophilus, on texture, proteolysis and related properties of Minas fresh cheese during storage at 5 degrees C was investigated. Three cheese-making trials were prepared and produced with no addition of cultures (T1 - control), supplemented with La-5 (T2), and with La-5 + S. thermophilus (T3). Viable counts of La-5 remained above 6.00 log cfu g(-1) during the whole storage for T2, reaching 7.00 log cfu g(-1) on the 14th day. For T3, the counts of La-5 remained above 6.00 log cfu g(-1) after 7 days of storage. Due to the presence of S. thermophilus, T3 presented the highest proteolytic index increase and titratable acidity values. Nevertheless, these results and S. thermophilus addition had no influence on viability of La-5 which presented satisfactory populations for a probiotic food. Moreover, the use of a yoghurt culture for the production of Minas fresh cheese T3 supplemented with La-5 resulted in a good quality product, with a small rate of post-acidification, indicating that traditional yoghurt culture could be employed in co-culture with La-5 to improve the quality of this cheese. (C) 2008 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.

Monitoring the authenticity of Brazilian UHT milk: A chemometric approach

In this work, chemometric methods are reported as potential tools for monitoring the authenticity of Brazilian ultra-high temperature (UHT) milk processed in industrial plants located in different regions of the country. A total of 100 samples were submitted to the qualitative analysis of adulterants such as starch, chlorine, formal. hydrogen peroxide and urine. Except for starch, all the samples reported, at least, the presence of one adulterant. The use of chemometric methodologies such as the Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) enabled the verification of the occurrence of certain adulterations in specific regions. The proposed multivariate approaches may allow the sanitary agency authorities to optimise materials, human and financial resources, as they associate the occurrence of adulterations to the geographical location of the industrial plants. (c) 2010 Elsevier Ltd. All rights reserved.

Acai pulp addition improves fatty acid profile and probiotic viability in yoghurt

The effects of acai pulp addition and different probiotic bacteria on the fatty acid profile of stirred yoghurt were examined. Skim milk was divided into two groups: one containing acai pulp and another without the fruit. Batches were inoculated with yoghurt starter culture and divided into five groups according to probiotic addition. Counts of viable microorganisms were measured at days 1, 14 and 28 of cold storage. Fatty acid profile was determined by gas chromatography at day 1. Acai pulp favoured an increase in Lactobacillus acidophilus L10, Bifidobacterium animalis ssp. lactis Bl04 and Bifidobacterium longum Bl05 counts at the end of 4 weeks of cold storage. This study demonstrated that acai pulp addition increased monounsaturated and polyunsaturated fatty acid contents in probiotic yoghurt and enhanced the production of cc-linolenic and conjugated linoleic acids during fermentation of skim milk prepared with B. animalis ssp. lactis Bl04 and B94 strains. (C) 2010 Elsevier Ltd. All rights reserved.

Electrical impedance particle size method (Coulter Counter) detects the large fat globules in poorly homogenised UHT processed milk

The large fat globules that can be present in UHT milk due to inadequate homogenisation cause a cream layer to form that limits the shelf life of UHT milk. Four different particle size measurement techniques were used to measure the size of fat globules in poorly homogenised UHT milk processed in a UHT pilot plant. The thickness of the cream layer that formed during storage was negatively correlated with homogenisation pressure. It was positively correlated with the mass mean diameter and the percentage volume of particles between 1.5 and 2 mu m diameter, as determined by laser light scattering using the Malvern Mastersizer. Also, the thickness of the cream layer was positively correlated with the volume mode diameter and the percentage volume of particles between 1.5 and 2 mu m diameter, as determined by electrical impedance using the Coulter Counter. The cream layer thickness did not correlate significantly with the Coulter Counter measurements of volume mean diameter, or volume percentages of particles between 2 and 5 mu m or 5 and 10 mu m diameter. Spectroturbidimetry (Emulsion Quality Analyser) and light microscopy analyses were found to be unsuitable for assessing the size of the fat particles. This study suggests that the fat globule size distribution as determined by the electrical impedance method (Coulter Counter) is the most useful for determining the efficiency of homogenisation and therefore for predicting the stability of the fat emulsion in UHT milk during storage.

Age gelation of UHT milk - A review

Gelation of UHT milk during storage (age gelation) is a major factor limiting its shelf-life. The gel which forms is a three-dimensional protein matrix initiated by interactions between the whey protein beta -lactoglobulin and the kappa -casein of the casein micelle during the high heat treatment. These interactions lead to the formation of a beta -lactoglobulin-kappa -casein complex (beta kappa -complex). A feasible mechanism of age gelation is based on a two-step process; in the first step, the beta kappa -complexes dissociate from the casein micelles due to the breakdown of multiple anchor sites on kappa -casein, and in the second step, these complexes aggregate into a three-dimensional matrix. When a critical volume concentration of the beta kappa -complex is attained, a gel of custard-like consistency is formed. Significant factors which influence the onset of gelation include the nature of the heat treatment, proteolysis during storage, milk composition and quality, seasonal milk production factors and storage temperature. In this review, age gelation is discussed in terms of these factors, causative mechanisms and procedures for controlling it.

A survey of Australian consumers' attitudes towards UHT milk

A telephone survey was conducted in Melbourne and Brisbane to obtain a profile of milk consumption in Australia and determine consumers' attitudes regarding UHT milk. It was anticipated that this survey would reveal the reasons for the low level of UHT milk consumption in Australia. Pasteurised milk was the main milk type used by more than 80% of respondents. For UHT milk this figure was much lower (approximately 10%), even though two thirds of respondents had tried UHT milk. Factors that were found to influence UHT milk consumption included existing milk consumption habits, consumer perception, flavour and price. The majority of non-users of UHT milk stated habit of using other milk type as their main reason for not using UHT milk. Other reasons included poor nutritional value, poor flavour and not real/pure milk, indicating a negative consumer perception of the product. The flavour of UHT milk was identified as a problem, with nearly half of UHT milk users considering it to be worse than the flavour of pasteurised milk. However, a small proportion of UHT milk users preferred the flavour of UHT milk, with the majority of them stating that it was creamier, richer and/or stronger than the flavour of pasteurised milk. Prior to post-farmgate deregulation, price was shown to discourage consumers from using UHT milk. At the time of the survey, post-farmgate prices in Victoria were deregulated resulting in UHT milk being priced below that of pasteurised milk in some instances. This was believed to contribute to a significantly higher market share of the product in Melbourne than in Brisbane.

Ultra-high-temperature (UHT) treatment of milk: comparison of direct and indirect modes of heating

UHT processing of milk and its subsequent storage causes several changes which affect the shelf-life of UHT milk although it remains 'commercially sterile'. These changes include whey protein denaturation, protein-protein interaction, lactose-protein interaction, isomerisation of lactose, Maillard browning, sulphydryl compound formation, formation of a range of carbonyl and other flavoursome compounds, and formation of insoluble substances. They ultimately reduce the quality and limit the shelf life of UHT milk through development of off-flavours, fat separation, age gelation and sedimentation. The extent of these changes depends on many factors, a major one being the type of UHT heating. This review compares the effect heating milk by direct and indirect modes on various aspects of processing and quality of UHT milk.

Evaluation of encapsulation techniques of probiotics for yoghurt

The health benefits provided by probiotic bacteria have led to their increasing use in fermented and other dairy products. However, their viability in these products is low. Encapsulation has been investigated to protect the bacteria in the product's environment and improve their survival. There are two common encapsulation techniques, namely extrusion and emulsion, to encapsulate the probiotics for their use in the fermented and other dairy products. This review evaluates the merits and limitations of these two techniques, and also discusses the supporting materials and special treatments used in encapsulation processes. (C) 2003 Elsevier Science Ltd. All rights reserved.