Salt in food processing; usage and reduction: a review

Salt is one of the most widely used additives in food industries because of its low cost and varied properties. It has a preservative and antimicrobial effect as a direct consequence of the capacity of sodium chloride to reduce water activity values. In addition, sodium chloride is a flavour enhancer as a consequence of its effect on different biochemical mechanisms. It also has flavour enhancing effects from reducing or enhancing the enzymatic activity of some enzymes responsible for the development of different organoleptic parameters. Trends in sodium chloride use in food industries point to salt replacement or reduction by means of the use of sodium chloride substitutes such as KCl or phosphates; flavour enhancers and the optimisation of the physical form of salt. This trend has arisen as a result of the greater awareness of the negative effects of excess dietary intake of sodium, which has been linked to hypertension and consequently an increased risk of cardiovascular disease. The average total daily sodium intake per individual in developed countries is 4–5 g of Na, which is up to 25 times greater than the minimum adult requirement.     

Validation of the performance of a GMO multiplex screening assay based on microarray detection

A new screening method for the detection and identification of GMO, based on the use of multiplex PCR followed by microarray, has been developed and is presented. The technology is based on the identification of quite ubiquitous GMO genetic target elements first amplified by PCR, followed by direct hybridisation of the amplicons on a predefined microarray (DualChip^® GMO, Eppendorf, Germany). The validation was performed within the framework of a European project (Co-Extra, contract no 007158) and in collaboration with 12 laboratories specialised in GMO detection. The present study reports the strategy and the results of an ISO complying validation of the method carried out through an inter-laboratory study. Sets of blind samples were provided consisting of DNA reference materials covering all the elements detectable by specific probes present on the array. The GMO concentrations varied from 1% down to 0.045%. In addition, a mixture of two GMO events (0.1% RRS diluted in 100% TOPAS19/2) was incorporated in the study to test the robustness of the assay in extreme conditions. Data were processed according to ISO 5725 standard. The method was evaluated with predefined performance criteria with respect to the EC CRL method acceptance criteria. The overall method performance met the acceptance criteria; in particular, the results showed that the method is suitable for the detection of the different target elements at 0.1% concentration of GMO with a 95% accuracy rate. This collaborative trial showed that the method can be considered as fit for the purpose of screening with respect to its intra- and inter-laboratory accuracy. The results demonstrated the validity of combining multiplex PCR with array detection as provided by the DualChip^® GMO (Eppendorf, Germany) for the screening of GMO. The results showed that the technology is robust, practical and suitable as a screening tool.     

Hydroxyl radical formation upon oxidation of reduced humic acids by oxygen in the dark

Humic acids (HAs) accept and donate electrons in many biogeochemical redox reactions at oxic/anoxic interfaces. The products of oxidation of reduced HAs by O(2) are unknown but are expected to yield reactive oxygen species, potentially including hydroxyl radical (·OH). To quantify the formation of ·OH upon oxidation of reduced HAs by O(2), three HAs were reduced electrochemically to well-defined redox states and were subsequently oxidized by O(2) in the presence of the ·OH probe terephthalate. The formation of ·OH upon oxidation increased with increasing extent of HA reduction. The yield of ·OH ranged from 42 to 160 mmol per mole of electrons donated by the reduced HA. The intermediacy of hydrogen peroxide (H(2)O(2)) in the formation of ·OH was supported by enhancement of ·OH formation upon addition of exogenous H(2)O(2) sources and by the suppression of ·OH formation upon addition of catalase as a quencher of endogenous H(2)O(2). The formation of ·OH in the dark during oxidation of reduced HA represents a previously unknown source of ·OH formation at oxic/anoxic interfaces and may affect the biogeochemical and pollutant redox dynamics at these interfaces.     

Phenolic profile of blackberry wine produced using Korean winemaking techniques in earthenware jars

This research evaluated the winemaking potential of ‘Natchez’ and ‘Triple Crown’ blackberries grown in Oklahoma and examined the phenolic composition of blackberry wines made using modified Korean traditional winemaking techniques. The winemaking variables were fermentation temperature (21.6 vs 26.6°C), and fermentation type (yeast inoculation vs wild fermentation). High‐performance liquid chromatography was used to examine the phenolic compounds in blackberry juice and wine. The phenolic compounds consisted of anthocyanins (kuromanin, keracyanidin, delphinidin) and phenolic acids (gallic acid, catechin, caffeic acid, epicatechin, p‐coumaric acid). The ‘Natchez’ berries had higher concentrations of anthocyanins (kuromanin) while ‘Triple Crown’ berries had higher levels of phenolic acids (p‐coumaric acid). For many compounds, a higher fermentation temperature generally corresponded to higher concentrations of the phenolic compound in the wine after three months aging, but this was not universally observed. Accordingly, fermentation temperature may best be matched with individual cultivars via experimentation in order to maximise extraction and retention of phenolic compounds in the finished wines. Overall, the Korean traditional winemaking technique may be a good technique to add value to wines made from blackberries suited for production in a mid‐continental climate such as the central USA. © 2018 The Institute of Brewing & Distilling     

Behavior of Listeria monocytogenes inoculated on cantaloupe surfaces and efficacy of washing treatments to reduce transfer from rind to fresh-cut pieces

Attachment and survival of Listeria monocytogenes on external surfaces (rind) of inoculated cantaloupe, resistance of the surviving bacteria to chlorine or hydrogen peroxide treatments, transfer of the pathogen from unsanitized and sanitized rinds to fresh-cut tissues during cutting and growth, and survival of L. monocytogenes on fresh-cut pieces of cantaloupe were investigated. Surface treatment with 70% ethanol to reduce the native microflora on treated melon, followed by immersion in a four-strain cocktail of L monocytogenes (10(8) CFU/ml) for 10 min, deposited 4.2 log10 CFU/cm2 and 3.5 log10 CFU/cm2 of L monocytogenes on treated and untreated cantaloupe rinds, respectively. L. monocytogenes survived on the treated or untreated cantaloupe rinds for up to 15 days during storage at 4 and 20 degrees C, but populations declined by approximately 1 to 2 log10 CFU/cm2. Fresh-cut pieces prepared from inoculated whole cantaloupes stored at 4 degrees C for 24 h after inoculation were positive for L. monocytogenes. Washing inoculated whole cantaloupes in solutions containing 1,000 ppm of chlorine or 5% hydrogen peroxide for 2 min at 1 to 15 days of storage at 4 degrees C after inoculation resulted in a 2.0- to 3.5-log reduction in L. monocytogenes on the melon surface. Fresh-cut pieces prepared from the sanitized melons were negative for L. monocytogenes. After direct inoculation onto fresh-cut pieces, L. monocytogenes survived, but did not grow, during 15 days of storage at 4 degrees C. Growth was evident by 4 h of storage at 8 and 20 degrees C. It is concluded that sanitizing with chlorine or hydrogen peroxide has the potential to reduce or eliminate the transfer of L. monocytogenes on melon surfaces to fresh-cut pieces during cutting.     

Enhancement of hematite bioreduction by natural organic matter

The effects of natural organic matter (NOM), ferrozine, and AQDS (anthraquinone-2,6-disulfonate) on the reduction of hematite (alpha-Fe2O3) by Shewanella putrefaciens CN32 were studied. It has been proposed that NOM enhances the reduction of Fe(III) by means of electron shuttling or by Fe(II) complexation. Previously both mechanisms were studied separately using "functional analogues" (AQDS for electron shuttling and ferrozine for complexation) and are presently compared with seven different NOMs. AQDS enhanced hematite reduction within the first 24 h of incubation, and this had been ascribed to electron shuttling. Most of the NOMs enhanced hematite reduction after 1 day of incubation indicating that these materials could also serve as electron shuttles. The effect of ferrozine was linear with concentration, and all of the NOMs exhibited this behavior. Fe(II) complexation only enhanced hematite reduction after sufficient Fe(II) had accumulated in the system. Fe(II) complexation appeared to alleviate a suppression of the hematite reduction rate caused by accumulation of Fe(II) in the system. Addition of Fe(II) to the hematite suspension, prior to inoculation with CN32, significantly inhibited hematite reduction and greatly diminished the effects of all of the organic materials, although some enhancement was observed due to addition of anthroquinone-2,6-disulfonate. These results demonstrate that NOM can enhance iron reduction by electron shuttling and by complexation mechanisms.     

Specific UV absorbance of Aldrich humic acid: changes during transport in aquifer sediment

This study examined the transport behavior of Aldrich humic acid (AHA) in low natural organic carbon content sediment contaminated with tetrachloroethene (PCE), for comparison to a nonionic surfactant mixture previously examined in the same system. Tracking of individual molecular weight (MW) fractions of AHA was attempted by UV absorbance, followed by conversion to mass of carbon using specific ultraviolet absorbance (SUVA) (UV absorbance per mass of carbon) measurements. The analysis required determination of variations of SUVA with MW, which showed a maximum at 10 000 Daltons. Furthermore, SUVAs of AHA MW fractions greater than about 10 000 Daltons increased following AHA interaction with sediment in batch experiments, and this was associated with AHA-driven leaching of cations from the sediment. AHA transport was examined in a series of three columns representing the up-gradient, residual-zone, and down-gradient portions of a DNAPL contaminated site. SUVAs of larger MW AHA fractions cycled through decreased, increased, and eventual return to influent values during the early, intermediate, and final stages of breakthrough, respectively. These variations were attributable to a combination of preferential adsorption of low MW fractions of the AHA during early breakthrough and AHA-driven leaching of sediment cations during intermediate breakthrough, with eventual exhaustion of sediment cation complexation during the final stage of breakthrough. The complex variations in SUVA precluded accurate conversion of measured UV absorbance to carbon mass. However, the effect of AHA loss to sediment on the solubilizing capacity of the AHA solution was indicated by the breakthrough behavior of AHA-solubilized PCE, which showed that AHA loss from the aqueous phase during transport in this system did not decrease the solubilizing capacity of the AHA mixture.     

Measurement and dynamic modeling of trace metal mobilization in soils using DGT and DIFS

The technique of diffusive gradients in thin-films (DGT) accumulates metals on a Chelex resin after their diffusive transport through a hydrogel. It lowers metal concentrations in soil solution adjacent to the device and induces resupply of metal associated with the solid phase. DGT devices were deployed in an alluvial gley soil for 21 different time periods between 4 h and 19.5 d. The accumulated masses of Cu, Cd, Ni, and Zn were used to calculate the distribution coefficient for labile metal, Kdl, and adsorption and desorption rate constants. Calculations were performed using a dynamic numerical model of DGT-induced fluxes in soils (DIFS). It assumes first-order exchange between solid phase and solution and diffusional transport in both the soil solution and the hydrogel. The DIFS model fitted changes in accumulated mass with time very well. Values of Kdl calculated from DIFS of 100 (Cd), 250 (Cu), 150 (Ni), and 150 (Zn) were larger than values of distribution coefficients estimated by exchange with Ca(NO3)2 but similar to those estimated by isotopic exchange (Cd and Zn only). These results suggest that the solid-phase pool of metal affected by the removal of labile metal by DGT, which operates on a time scale of minutes, is similar to the solid-phase pool of metal that can isotopically exchange with solution on a time scale of 2 d. Response times of minutes were consistent with interaction rates with surfaces, and desorption rate constants agreed with other reported values. An appraisal of the DIFS model demonstrated the importance of the labile pool size in the solid phase for controlling supply to a sink, such as DGT or a plant. As values of Kdl and kinetic parameters are obtained using DGT with minimal soil disturbance and by a similar mechanism to that involved in plant uptake, they may be pertinent to bioavailability studies.     

Effect of UV irradiation on organic matter extracted from treated Ohio River water studied through the use of electrospray mass spectrometry

Ohio River water was treated by settling, sand filtration, and granular activated carbon filtration. It was then irradiated by low-pressure (monochromatic) and medium-pressure (polychromatic) UV lamps to investigate the effects of UV irradiation on the extracted organic matter (EOM). When the EOM, collected by solid phase extraction cartridges, was analyzed by conventional UV spectroscopy and size exclusion chromatography (SEC), no significant changes in the EOM were revealed for various UV doses. Positive and negative electrospray ionization mass spectrometry (ESI-MS) of the EOM produced mass spectra that vary significantly with UV dose. The UV dosage conditions also appear to affect the reactivity of the EOM to subsequent chlorination. The magnitude of the spectral changes is generally greater for medium-pressure lamps than for low pressure and increases with UV exposure. Based on the observed MS peaks, the changes may be due to the presence of lignin, resulting perhaps from photooxidation and/or photo rearrangement of macromolecules in the sample. When chlorination is used for secondary disinfection, these results suggest that it may be important to consider the effects of UV irradiation on the organic matter in the water before applying UV disinfection technology to a particular source water.     

Detection of <Emphasis Type="Italic">Campylobacter</Emphasis> colonies using hyperspectral imaging

The presence of Campylobacter in foods of animal origin is the leading cause of bacterially induced human gastroenteritis. Isolation and detection of Campylobacter in foods via direct plating involves lengthy laboratory procedures including enrichments and microaerobic incubations, which take several days to a week. The incubation time for growing Campylobacter colonies in agar media usually takes 24–48 h. Oftentimes the problem is the difficulty of visually differentiating Campylobacter colonies from non-Campylobacter contaminants that frequently grow together with Campylobacter on many existing agars. In this study, a new screening technique using non-destructive and non-contact hyperspectral imaging was developed to detect Campylobacter colonies in Petri dishes. A reflectance spectral library of Campylobacter and non-Campylobacter contaminants was constructed for characterization of absorption features in wavelengths from 400 to 900 nm and for developing classification methods. Blood agar and Campy-Cefex agar were used as culture media. The study found that blood agar was the better culture medium than Campy-Cefex agar in terms of Campylobacter detection accuracy. Classification algorithms including single-band thresholding, band-ratio thresholding and spectral feature fitting were developed for detection of Campylobacter colonies as early as 24 h of incubation time. A band ratio algorithm using two bands at 426 and 458 nm chosen from continuum-removed spectra of the blood agar bacterial cultures achieved 97–99% of detection accuracy. This research has profound implications for early detection of Campylobacter colonies with high accuracy. Also, the developed hyperspectral reflectance imaging protocol is applicable to other pathogen detection studies.