Factors affecting the changes in texture of dressed ("aliñadas") olives

The effect of the natural components of dressing during the conservation of olives on their texture was studied. Significant differences in texture between preparations with and without dressing were detected, although the texture in both preparations continued to diminish with time of conservation until the difference between textures was eliminated. These facts suggest that the enzymes coming from the constituents of the dressing (garlic, lemon, etc), as well as those endogenous enzymes in the olive fruit itself influence the changes in the texture, the olive becoming more susceptible to dressing and to enzymatic action as the stage of maturation progresses. Changes in the composition of polysaccharides and significant decreases in texture were related. Degradation of important polysaccharides in the structure of cell walls, such as !-cellulose, carbonate-soluble pectin and 4% KOH-soluble hemicelluloses were detected. This noticeable degradation could be explained perfectly by the combined action of the cell wall degrading enzymes, cellulase and polygalacturonase, present.     

To Remove or Not to Remove? The Challenge of Extracting the Template to Make the Cavities Available in Molecularly Imprinted Polymers (MIPs)

Template removal is a critical step in the preparation of most molecularly imprinted polymers (MIPs). The polymer network itself and the affinity of the imprinted cavities for the template make its removal hard. If there are remaining template molecules in the MIPs, less cavities will be available for rebinding, which decreases efficiency. Furthermore, if template bleeding occurs during analytical applications, errors will arise. Despite the relevance to the MIPs performance, template removal has received scarce attention and is currently the least cost-effective step of the MIP development. Attempts to reach complete template removal may involve the use of too drastic conditions in conventional extraction techniques, resulting in the damage or the collapse of the imprinted cavities. Advances in the extraction techniques in the last decade may provide optimized tools. The aim of this review is to analyze the available data on the efficiency of diverse extraction techniques for template removal, paying attention not only to the removal yield but also to MIPs performance. Such an analysis is expected to be useful for opening a way to rational approaches for template removal (minimizing the costs of solvents and time) instead of the current trial-and-error methods.     

Evaluation of growth/no growth interface of Listeria monocytogenes growing on stainless steel surfaces, detached from biofilms or in suspension, in response to pH and NaCl

The present study aimed to describe the growth/no growth interface of Listeria monocytogenes at three potential states of growth in industrial environments, namely attached, (Att), detached (Det) from a biofilm, or in a planktonic state (suspended; Plan). A 3-strain composite of L. monocytogenes cells was left to colonize stainless steel (SS) surfaces in tryptic soy broth supplemented with 0.6% yeast extract (TSBYE) at 20 °C for 72 h and then transferred to TSBYE at 30 different pH and NaCl concentrations, which were renewed every two days during incubation at 10 °C. Survival of attached population was observed at optimal conditions (pH 7.2, a(w) 0.996), whereas at 4.5-8.0% salt and/or pH<6.0, reduction of attached population on SS surfaces was observed. PFGE patterns showed that 91% of the cells colonizing the SS coupons after 30 days, at any pH and a(w) conditions, belonged to a single strain. Furthermore, the change in the probability of a single cell to initiate growth (P(in)) over time, as well as the number of cells needed (CN) for growth initiation of planktonically growing Plan and Det L. monocytogenes cells were evaluated based on MPN Tables. An ordinary logistic regression model was also used to describe the growth/no growth interface of varying inoculation levels (from <10 to 10(4)CFU/ml) of Plan and Det cells in response to pH and a(w). Although both cell types demonstrated similar growth limits at populations of 10(2)-10(4)CFU/ml, higher numbers of Det than Plan cells were needed (CN) in order to initiate growth at low a(w) and pH. Individual Plan cells reached higher maximum levels of probability of growth initiation (P(max)) and had shorter times to reach P(max)/2 (t(au)), compared to their Det counterparts. Data on growth potential of cells in suspension, attached or detached status, may assist in ranking the risk from different sources of contamination. In addition, they may establish the link between the behavior of L. monocytogenes in foods and its origin from the processing plant. The latter link is important component of biotraceability.     

Highly Conductive Redox Protein–Carbon Nanotube Complex for Biosensing Applications

The integration of redox proteins with nanomaterials has attracted much interest in the past years, and metallic single‐walled carbon nanotubes (SWNTs) have been introduced as efficient electrical wires to connect biomolecules to metal electrodes in advanced nano‐biodevices. Besides preserving biofunctionality, the protein–nanotube connection should ensure appropriate molecular orientation, flexibility, and efficient, reproducible electrical conduction. In this respect, yeast cytochrome c redox proteins are connected to gold electrodes through lying‐down functionalized metallic SWNTs. Immobilization of cytochromes to nanotubes is obtained via covalent bonding between the exposed protein thiols and maleimide‐terminated functional chains attached to the carbon nanotubes. A single‐molecule study performed by combining scanning probe nanoscopies ascertains that the protein topological properties are preserved upon binding and provides unprecedented current images of single proteins bound to carbon nanotubes that allow a detailed I–V characterization. Collectively, the results point out that the use as linkers of suitably functionalized metallic SWNTs results in an electrical communication between redox proteins and gold electrodes more efficient and reproducible than for proteins directly connected with metal surfaces.     

Influence of pentosans on texture of starch gels during storage,and effects after enzyme treatment

The effects of commercial soluble (SAX) and insoluble (IAX) arabinoxylans (AX), and water extractable pentosans (WEP) from wheat doughs on texture profile analysis (TPA) of starch gels have been determined. Gels were also subjected to enzyme treatment with a amylase/pentosanase preparation, a lipase and their combination. SAX delayed starch gel aging and gave more cohesive and less elastic gels than starch, whereas IAX showed only a slight influence. With their combination the TPA of gels showed a predominant effect of SAX. The effect of enzyme addition was enhanced in presence of AX, but they did not improve the effect of AX without treatment. When WEP were used the addition of enzymes was more effective in delaying gel staling. Kinetics of aging depended on the type of AX present and the enzyme combination used to prepare the starch gels.     

Grape Processing by High Hydrostatic Pressure: Effect on Microbial Populations,Phenol Extraction and Wine Quality

Food and Bioprocess Technology - Vitis vinifera (variety Tempranillo) grapes were subjected to high hydrostatic pressure (HHP) treatments of 200, 400 and 550&nbsp;MPa for 10&nbsp;min, and...     

Serum concentrations of 11 polyfluoroalkyl compounds in the u.s. population: data from the national health and nutrition examination survey (NHANES)

We measured the concentrations of 11 polyfluoroalkyl compounds (PFCs), including perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and perfluorohexane sulfonic acid (PFHxS) in 1562 serum samples collected from a representative U.S. population 12 years of age and older in the 1999-2000 National Health and Nutrition Examination Survey. Participants represented both sexes, three race/ethnicities (non-Hispanic blacks, non-Hispanic whites, and Mexican-Americans), and four age categories (12-19 years, 20-39 years, 40-59 years, and 60 years and older). PFCs were extracted from 100 microL of serum using on-line solid-phase extraction coupled to isotope dilution-high performance liquid chromatography-tandem mass spectrometry; limits of detection ranged from 0.05 to 0.2 ng/ mL. PFOS, PFOA, PFHxS, and perfluorooctane sulfonamide were detected in all samples analyzed; 2-(N-ethyl-perfluorooctane sulfonamido) acetic acid, 2-(N-methyl-perfluorooctane sulfonamido) acetic acid, and perfluorononanoic acid were detected in more than 90% of samples, which suggests prevalent exposures to several PFCs in the U.S. population. The concentrations of most PFCs were similar regardless of the participants' ages but were higher in males than in females. Mexican Americans had lower concentrations than non-Hispanic blacks and non-Hispanic whites, whose concentrations were similar. Higher education was associated with higher concentrations of PFOS and PFOA. These data will serve as a nationally representative baseline of the U.S. population's exposure to PFCs to which other populations can be compared, and will play an important role in public health by helping set research priorities, ranging from health effects studies to defining sources and pathways of exposure.     

Assessment of the Influence of the Decanter Set-up During Continuous Processing of Olives at Different Pigmentation Index

New generation decanters allow operators to make real-time adjustments during the virgin olive oil extraction process in order to gain the best performance possible. However, the opportunity to act in line requires a deep understanding of the consequences of changing machine parameters. To this purpose, an experiment was carried out at industrial scale. The decanter feed rate (Fr), ranging from 4075 to 5820 kg h^?1, the bowl/screw conveyor differential speed (?n), set at 18 and 22, and two ripening degrees of the olives were considered as process variables. Two combinations Fr-?n, namely 4620 kg h^?1 at ?n-18 and 5210 kg h^?1 at ?n-22, were found to similarly maximize the process efficiency, regardless the raw material features. After pointing out the best working settings, the corresponding virgin olive oils were compared. The analysis of variance showed that peroxide value, K ₂₃₂, K ₂₇₀, phenols, chlorophylls, β-tocopherol, fruity and bitter notes, and C6 volatile compounds were significantly affected by the machine parameters. An inverse proportionality was observed between the combination Fr-?n and the phenolic compounds. On the whole, the sampling factor exerted a larger influence on the product quality than the decanter set-up.     

Regulation of acetic acid production by homo-and heterofermentative lactobacilli in whole-wheat sour-doughs

The efficiency of sour-dough as a possible preservative agent of microbial spoilage of bread depends on its acetic acid content. As a secondary metabolite of sugar fermentation by lactic acid bacteria, acetic acid may be promoted in the presence of O₂ or H⁺ acceptors. This paper studies the influence of O₂ and high fructose content products (pure sugar, invert sugar, fructose syrup) addition on acetic acid production by hetero- (Lactobacillus brevis 25a, B-21, L-62;L. sanfrancisco L-99) and homofermentative (L. plantarum B-39) lactobacilli in whole-wheat sour-doughs [280 and 250 dough yield (DY)]. The pH and total titratable acidity (TTA) of sour-doughs after 44 h fermentation varied with DY and strain. As expected, the addition of O₂ promoted greater increases in TTA with heterofermentative lactobacilli (15–42%) than withL. plantarum (15%). Fructose addition was only effective for heterofermentative strains, but the overall effects were smaller than those observed for oxygenation. The ability of lactobacilli to produce acetic acid in sour-doughs without treatment varied from 0.16 g/100 g flour at 44 h (B-39, 280, 350 DY) to 0.47–0.65% (L-62, 280, 350 DY). The production of acetic acid was positively promoted by all treatments. Oxygenation was again the most effective way of inducing acetic acid production; increases ranged from 54% (B-21) to 269% (L-99, 350 DY). The addition of H⁺ acceptors had variable effects. Pure fructose resulted, in general, in greater increases than invert sugar of fructose syrup. The main effects were detected forL. brevis 25a (280 DY) B-21 (350 DY) andL sanfrancisco L-99 (350 DY) with increases ranging from 92 to 123%. The highest levels of acetic acid (1.02–1.04%) corresponded to sour-doughs (44 h, 35° C shaking 150 rpm) started with L-62 (280, 350 DY) or L-99 (350 DY).

---

Beeinflussung der Essigsäurebildung durch homo- und heterofermentative Laktobacillen in Weizenvollkornsauerteigen

Zusammenfassung Die Haltbarkeit von Sauerteig-Brot gegen mikrobiologische Verderbnis beruht auf seinem Säuregehalt. Als sekundäres Stoffwechselprodukt der Zuckergärung durch Milchsäurebakterien, kann die Essigsäure-Bildung von Sauerstoff- oder Wasserstoffacceptoren gefördert werden. Diese Veröffentlichung befaßt sich mit dem Einfluß von Sauerstoff und Produkten mit hohem Fructosegehalt (Rohrzucker, Invertzucker, Fructose-Sirup) auf die Essigsäure-Bildung durch hetero- (Lactobacillus brevis B-21, 25a, L-62;L. sanfrancisco L-99) und homofermentative (L. plantarum B-39) Laktobacillen in Weizenvollkornsauerteigen (TA 280 und 350). ph-Wert und Säuregrad von Sauerteigen nach 44-stündiger Gärung waren verschieden je nach TA und Stamm. Wie erwartet, verursachte die Zugabe von Sauerstoff eine größere Zunahme des Säuregrades mit heterofermentativen Laktobacillen (15–42%) als mitL. plantarum (15). Fructose-Zugabe war nur wirksam für die heterofermentativen Stämme, aber die allgemeinen Wirkungen waren kleiner als die bei der Behandlung mit Sauerstoff beobachteten. Die Fähigkeit von Laktobazillen, ohne Behandlung in Sauerteigen Essígsäure zu bilden, schwankte zwischen 0.16 g/100 g Mehl (B-39, 280, 350 TA) und 0.47–0.65% (L-62, 280, 350 TA). Die Bildung von Essigsäure wurde durch alle Behandlungen gefördert. Die Behandlung mit Sauerstoff war wieder die effizienteste zur Förderung der Essigsäurebildung; der Anstieg schwankte zwischen 54% (B-21) und 269% (L-99, 350 TA). Die Zugabe von Wasserstoffacceptoren hatte verschiedene Effekte. Reine Fructose ergab im allgemeinen größere Anstiege als Invertzucker oder Fructose Sirup. Die Haupteffekte wurden beiL. brevis 25a (280 TA), B-21 (350 TA) undL. sanfrancisco L-99 (350 TA) mit Anstiegen von 92% bis 123% nachgewiesen. Die mit L-62 (280, 350 TA) oder L-99 (350 TA) hergestellten Sauerteige (44 h, 35 °C, 150 rpm schütteln) ergaben die höchste Gehalte an Essigsäure (1.02–1.04%).