[Prebiotics: concept, properties and beneficial effects]

Prebiotics are non-digestible food ingredients (oligosaccharides) that reach the colon and are used as substrate by microorganisms producing energy, metabolites and micronutrients used for the host; in addition they also stimulate the selective growth of certain beneficial species (mainly bifidobacteria and lactobacilli) in the intestinal microbiota. In this article, a multidisciplinary approach to understand the concept of prebiotic carbohydrates, their properties and beneficial effects in humans has been carried out. Definitions of prebiotics, reported by relevant international organizations and researchers, are described. A comprehensive description of accepted prebiotics having strong scientific evidence of their beneficial properties in humans (inulin-type fructans, FOS, GOS, lactulose and human milk oligosaccharides) is reported. Emerging prebiotics and those which are in the early stages of study have also included in this study. Taken into account that the chemical structure greatly influences carbohydrates prebiotic properties, the analytical techniques used for their analysis and characterization are discussed. In vitro and in vivo models used to evaluate the gastrointestinal digestion, absorption resistance and fermentability in the colon of prebiotics as well as major criteria to design robust intervention trials in humans are described. Finally, a comprehensive summary of the beneficial effects of prebiotics for health at systemic and intestinal levels is reported. The research effort on prebiotics has been intensive in last decades and has demonstrated that a multidisciplinary approach is necessary in order to claim their health benefits.

Ureteral spindle cell sarcoma in a dog

A five-year-old, female spayed Labrador retriever was presented for further investigation of an intra-abdominal mass. Abdominal exploration showed a large mass arising from the right ureter and a ureteronephrectomy was performed. Histopathology of the ureteral mass was consistent with a spindle cell sarcoma. The patient recovered well, but five months later was diagnosed with another tumour, this time in her left abdominal wall. The owners decided not to pursue further treatment and euthanasia was performed a month later.

Purification of lactulose from mixtures with lactose using pressurized liquid extraction with ethanol-water at different temperatures

The viability of the purification of lactulose from a mixture with lactose [70:30 (w/w)] using pressurized liquid extraction (PLE) at 1500 psi for 30 min was studied. Different temperatures (from 40 to 130 degrees C) and proportions of ethanol:water (70:30, 80:20, 90:10, 95:5, and 100:0) as the extraction solvent were assayed. Lactose and lactulose were measured by gas chromatographic analysis as their trimethylsilyl derivatives. Data were fitted through multiple linear regressions to different quadratic models to describe both the extraction yield (in terms of mg of lactulose) and the purity of the lactulose extracted. The optimum extraction conditions provided by the model were as follows: extraction temperature, 40 degrees C; and solvent composition, 70:30 ethanol:water. PLE extraction under the optimized conditions was also applied to purify lactulose from lactose in a synthesis mixture. To our knowledge, this is the first time that PLE has been tested for extraction and purification of lactulose from its mixture with lactose; this technique showed several advantages over classical methods such as the short extraction time and the low solvent consumption.

Use of Chitosan for Selective Removal of β-Lactoglobulin from Whey

A method is described for selective removal of undenatured beta-lactoglobulin from cheese whey based on interactions between whey proteins and chitosan. Whey was previously clarified at pH 4.5 with addition of chitosan (25 mg/100 mL), and selective removal of beta-lactoglobulin was studied in the pH interval 4.6 to 6.5. Addition of chitosan caused selective precipitation of beta-lactoglobulin that increased with pH. The content of beta-lactoglobulin in whey decreased as the amount of chitosan added was increased. At pH 6.2, addition of 1.9 to 3.0 mg/mL of chitosan led to complete removal of beta-lactoglobulin, whereas at least 80% of the rest of whey proteins remained in solution. The production of cheese whey without beta-lactoglobulin could help to expand the applications of dairy by-products in food processing, and to isolate hypoallergenic whey protein concentrates.

Selective recovery of glycosylated caseinmacropeptide with chitosan

The use of chitosan, a partially deacetylated chitin, to fractionate aqueous solutions of caseinmacropeptides (CMPs) was studied. The polycationic character of chitosan at acidic pH values allows the formation of complexes with negatively charged CMP molecules, inducing their flocculation. Glycosylated CMP (GMP) has higher affinity for chitosan than nonglycosylated forms (NGMP). The carboxylic groups in the carbohydrate moiety of the GMP increase the negative charge of the molecule and may play a role in the selective precipitation. At pH 5.0, 0.08 mg/mL of chitosan completely removed the GMP whereas 70% of NGMP remained in solution. As the pH increased, the amount of chitosan to ensure complete removal of GMP increased up to 0.19 and 0.34 mg/mL for pH 6.0 and 6.6, respectively.

Clinical and radiographic study of bone and joint lesions in 26 dogs with leishmaniasis

Twenty-six dogs with parasitologically confirmed leishmaniasis and abnormalities of gait were studied to determine the most common radiological patterns of bone and joint lesions. The clinical findings included either lameness, joint pain and crepitation, soft tissue swelling and/or muscle atrophy. Bone lesions were observed radiographically in 12 of the 26 dogs; the radius and ulna were affected in seven, the tibia in six and the femur in six. Joint lesions were observed radiographically in 15 of the 26 dogs; the carpus and stifle were affected in all 15, and the tarsus in nine. There was a tendency for the bones and joints to be affected bilaterally. The radiographic patterns observed were different in the long bones and the joints. In the long bones, the most common pattern was periosteal and intramedullary proliferation, involving the diaphyses and related to the nutrient foramen; in the joints, two patterns, either non-erosive or erosive polyarthritis with soft-tissue swelling, were observed. The changes observed in the synovial fluid were associated in most cases with osteolytic lesions. However, Leishmania organisms were identified in the synovial fluid from joints without bony radiographic changes.

Formation of Amadori compounds in dehydrated fruits

The presence of Amadori compounds in commercial dehydrated fruits has been shown through HPLC analysis of the corresponding 2-furoylmethyl-amino acids obtained by acid hydrolysis. Furosine (2-furoylmethyl-lysine) was the main 2-furoylmethyl derivative observed in dried figs and apricot samples, whereas in prunes and dates similar amounts of furosine and 2-furoylmethyl-gamma-aminobutyric acid were detected. A considerable variation of 2-furoylmethyl-amino acid contents among commercial raisin samples was observed. 2-Furoylmethyl-gamma-aminobutyric acid and 2-furoylmethyl-arginine, the most abundant 2-furoylmethyl-amino acids, ranged between 9.9 and 75.8 mg/100 g sample and 10.0 and 62.5 mg/100 g sample, respectively. Most of the Amadori compounds present in raisins seem to have originated during the commercial shelf life period rather than during processing. Determination of 2-furoylmethyl-amino acids could be used as a method of controlling commercial dehydrated fruit and selecting storage conditions.

Use of 2-furoylmethyl derivatives of GABA and arginine as indicators of the initial steps of maillard reaction in orange juice

The formation of 2-furoylmethyl derivatives of GABA (2-FM-GABA) and arginine (2-FM-Arg) as early indicators of nonenzymatic browning in different types of orange juice was studied. In dehydrated orange juice, the presence of 2-FM-GABA and 2-FM-Arg was detected from the first day of storage at 30 degrees C. In this type of juice, the content of these two compounds increased with temperature (30, 50 degrees C) and time (1-7 days) of storage. A noticeable increase in 5-hydroxymethylfurfural was only observed after 4 days of storage at 50 degrees C. No formation of 2-FM-GABA and 2-FM-Arg was detected in liquid orange juice heated under conditions similar to those used in the industry. These furoylmethyl derivatives were also found in commercial orange juice made from concentrates. A slight increase in their concentration was observed in the two samples stored during 8 months at room temperature. According to the results obtained, 2-FM-GABA and 2-FM-Arg contents could be suitable indicators to assess the main modifications due to Maillard reaction produced during the manufacture and/or storage of orange juice concentrates.

Survey of the furosine content in cheeses marketed in Spain

The furosine content in 53 samples of different cheese types (fresh, ripened with molds, artisanal hard-pressed, industrial hard-pressed, and processed) marketed in Spain was analyzed. The lowest furosine values were observed in artisanal hard-pressed cheeses (4.8 to 10.2 mg per 100 g of protein) and ripened with molds cheeses (4.2 to 12.8 mg per 100 g of protein). Industrial hard-pressed cheeses showed furosine values between 3.5 and 43.8 mg per 100 g of protein. Differences between samples may be attributed to the heat-treatment intensity given to cheese milk and to cheesemaking conditions. The highest contents of furosine were observed in processed cheeses (20 to 366.6 mg per 100 g of protein). A wide range of furosine content was found in fresh cheeses (17.9 to 73.6 mg per 100 g of protein), which could be due to the different amounts of dried milk added during the manufacture of cheeses.

Presence of 2-furoylmethyl derivatives in hydrolysates of processed tomato products

Acid hydrolysis of Amadori compounds yields the corresponding 2-furoylmethylamino acids (2-FM-AA) that can be analyzed by ion-pair HPLC. The relative proportions of the different 2-FM-AA present in the hydrolysates of tomato products were determined to assess their usefulness as indicators of quality. In the lyophilized tomato samples stored at 50 degrees C and a(w) = 0.44 the formation of 2-FM derivatives of alanine, gamma-aminobutyric acid (GABA), asparagine, aspartic acid, glutamic acid, lysine, serine, and threonine was detected. In commercial tomato products the most abundant 2-FM-AA was 2-FM-GABA (from traces to 26.4 mg/100 g of dry matter) followed by 2-FM-lysine (furosine). Differences in 2-FM-AA contents among samples may be related to processing and storage conditions.

Early stages of maillard reaction in dehydrated orange juice

The formation of furoylmethyl derivatives of amino acids as indicators of the early stages of Maillard reaction in dehydrated orange juices and model systems was studied. In stored dehydrated orange juices, the presence of furoylmethyl derivatives of arginine, asparagine, proline, alanine, glutamic acid, and GABA was detected. Their formation increased with temperature of storage. After 2 weeks at 30 degrees C and a(w) = 0.44, the reconstituted orange juice contained 94 mg/L furoylmethyl derivatives, whereas up to 1215 mg/L was detected in samples stored at 50 degrees C.

Synthesis and characterization of gamma-N-(2-furoylmethyl)aminobutyric acid

The product of acid hydrolysis of the Amadori compound gamma-N-(1-deoxy-D-fructosyl)aminobutyric acid was isolated and identified by (1)H NMR and (13)C NMR as gamma-N-(2-furoylmethyl)aminobutyric acid. This compound is an analogue to furosine, formed during acid hydrolysis of the corresponding Amadori compound. The retention time of the isolated compound was the same as that of the main peak observed in acid hydrolysates of stored orange juice powder. gamma-N-(2-Furoylmethyl)aminobutyric acid can be a useful indicator of the early stages of Maillard reaction in foods containing free gamma-aminobutyric acid.

Changes in the Amino Acid Composition of Dehydrated Orange Juice during Accelerated Nonenzymatic Browning

Maillard reaction in dehydrated orange juice stored at 30 or 50 degrees C and a(w) = 0.44 was studied. The decreases of the total amino acids were 30 and 65% of initial concentration after 14 days of storage at 30 and 50 degrees C, respectively. Storage at 50 degrees C for 14 days caused a decrease of 11.8 g/L of carbohydrates, and glucose was more reactive than fructose. Loss of sucrose due to hydrolysis was also observed. Presence of 1-(N-substituted)amino-1-deoxy-D-fructose compounds in stored dehydrated orange juice was detected by thin-layer chromatography.

Perfusion liquid chromatography of whey proteins

A perfusion reversed-phase (RP) HPLC method was developed for the rapid separation of the main bovine whey proteins: alpha-lactalbumin (alpha-LA), serum albumin (BSA) and the genetic variants of beta-lactoglobulin (A and B) (beta-LG A and beta-LG B). For the method development, the influence of factors favouring structural changes of proteins (temperature and organic acid concentration in the mobile phase), gradient and other chromatographic conditions and the mass of protein injected was examined. The optimized method allowed the separation of proteins in about 1.5 min (cycle time 3.5 min) with resolution around 1.0 for the beta-lactoglobulins. The method was applied to the determination of proteins in a whey from raw bovine milk. The precision of the determinations was < or = 3.75 mg per 100 ml (S.D.). With respect to the accuracy, errors < or = 7.0% in the determination of alpha-LA, beta-LG A and beta-LG B were obtained, compared with an RP-HPLC reference method. However, higher errors in the quantification of BSA were found owing to the lack of purity of the peak assigned. In addition, the proposed method has proved to be very useful in the detection of homologous whey proteins from different species (cow, sheep and goat) in milk mixtures.

Effects of continuous flow microwave treatment on chemical and microbiological characteristics of milk

Raw cows' and goats' milks were heated by microwave in a continuous flow unit up to temperatures ranging from 73.1 to 96.7 degrees C. The effects of the heat treatments were estimated by measurements of lactose isomerization, protein denaturation, inactivation of alkaline phosphatase and peroxidase and the total bacterial count. Negative phosphatase tests and low bacterial counts, together with low degrees of whey protein denaturation, were achieved under several temperature/time combinations. The results indicate that continuous microwave processing may be an efficient and mild approach for the pasteurization of milk.

Changes in furosine and proteins of UHT-treated milks stored at high ambient temperatures

Changes in furosine, undenatured whey protein content, and proteolysis during 90 days storage at 20, 30, and 40 degrees C of UHT-processed milk were studied. Furosine increased as the temperature and storage time increased. The peptide concentration increased during the storage period, being faster at 30 degrees C than at 20 or 40 degrees C. High-performance liquid chromatographic analysis of undenatured whey proteins showed considerable changes in the shape of the peaks during storage.

Proteolysis during storage of UHT milk: differences between whole and skim milk

Proteolysis during storage of UHT skim and whole milks processed by either direct or indirect systems has been studied. All the proteolysis indices determined (measurement of free amino groups, PAGE of caseins and PAGE and reversed-phase HPLC of the fraction soluble at pH 4.6) revealed greater proteolytic degradation during storage of skim milks compared with that of whole milks subjected to the same UHT treatments. Increased activities of both native milk proteinase and proteinases of bacterial origin were observed in skim UHT milks. The different behaviour of UHT skim and whole milks on storage would have to be taken into account in establishing the process conditions.

Effect of Storage Temperature on Lactulose and 5-hydroxymethyl-furfural Formation in UHT Milk

The amounts of two heating-induced products were studied (lactulose and 5-hydroxymethyl-furfural) in UHT milk samples, directly and indirectly heat-treated, during a period of 90 d storage at five different temperatures. The results indicate an increase in 5-hydroxymethyl-furfural, as well as lactulose, taking place in the range of temperatures between 40-50°C.