Bruce A. Welt

Cortical Networks Grown on Microelectrode Arrays As a Biosensor for Botulinum Toxin

Botulinum toxin (BoNT) is a potent neurotoxin produced by toxigenic strains of Clostridium botulinum. Botulinum toxin poses a major threat since it could be employed in a deliberate attack on the U.S. food supply. Furthermore, BoNT may be liberated in any insufficiently processed food containing a reduced oxygen atmosphere. Hence, rapid and reliable detection of BoNT in foods is necessary to reduce risks posed through food contamination. We present a BoNT biosensor employing living neural cultures grown in vitro on microelectrode arrays (MEAs). An MEA is a culture dish with a grid of electrodes embedded in its surface, enabling extracellular recording of action potentials of neural cultures grown over the array. Pharmaceutical grade BoNT A was applied to the media bath of mature cortical networks cultured on MEAs. Both spontaneous and evoked activities were monitored over 1 wk to quantify changes in the neural population produced by BoNT A. Introduction of BoNT A resulted in an increased duration and number of spikes in spontaneous and evoked bursts relative to control cultures. Increases were significant within 48 h of BoNT A dosage (P < 0.05). Application of BoNT A also induced unique oscillatory behavior within each burst that is reminiscent of early developmental activity patterns rather than the mature cultures used here. Three or more activity peaks were observed in 50% of the BoNT dosed cultures. Control cultures exhibited only a single activity peak. Thus activity of these cortical networks measured with MEAs could provide a valuable substrate for BoNT detection.

The impact of packaging materials on the antioxidant phytochemical stability of aqueous infusions of green tea (Camellia sinensis) and yaupon holly (Ilex vomitoria) during cold storage.

Ready to drink (RTD) teas are a growing segment in the beverage category, brought about by improvements in the flavor of these products and healthy market trends driven by consumers. The presented results evaluated the antioxidant phytochemical stability of RTD teas from aqueous infusions of traditional green tea (Camellia sinensis) and a botanical tea from yaupon holly (Ilex vomitoria) as influenced by packaging materials during cold storage. Two common packaging materials for RTD products are glass and polyethylene terephthalate (PET) and have been compared to a retortable pouch (RP), an emerging packaging material for various types of food since it is durable, inexpensive, lightweight, and easy to sterilize. Storage stability was then evaluated for each aqueous infusion prepared at 10 g/L at 90 °C for 10 min and evaluated at 3 °C in the absence of light over 12 weeks. Analyses included quantification and characterization of individual polyphenolics by high-performance liquid chromatography-photodiode array and liquid chromatography-electrospray ionization-mass spectrometry as well as changes in total antioxidant capacity. For green tea, concentrations of the three major flavan-3-ols, epigallocatechin gallate, epigallocatechin, and epicatechin gallate were better retained in glass bottles as compared to other packages over 12 weeks. In yaupon holly, chlorogenic acid and its isomers that were the predominant compounds were generally stable in each packaging material, and a 20.6-fold higher amount of saponin was found as compared to green tea, which caused higher stability of flavonol glycosides present in yaupon holly during storage. The antioxidant capacity of green tea was better retained in glass and PET versus RP, whereas no differences were again observed for yaupon holly. Results highlight the superiority of oxygen-impervious glass packaging, but viable alternatives may be utilizable for RTD teas with variable phytochemical compositions.

Muscle Quality of Yellowfin Tuna (Thunnus albacares) Steaks After Treatment with Carbon Monoxide Gases and Filtered Wood Smoke

ABSTRACT Treating seafood with carbon monoxide (CO) and various filtered wood smokes (FS) containing carbon monoxide has become a common practice in the industry, particularly for seafood intended for the frozen market. Tuna is one of the most common fish species treated with this process. Various quality improvement claims have been made for these treatments, which require investigation. Yellowfin tuna steaks were subjected to various CO treatments (4% CO, 18% CO and 100% CO) and FS treatment (which contained 18% CO) for 48 h, followed by 30 days of freezing and subsequent cold storage (4°C) after thawing. Muscle quality was evaluated after treatment. The FS, 18% CO and 100% CO treatments led to reductions in formation of secondary lipid oxidation products (TBARS) during freezing and subsequent cold storage, possibly due to increased stability of heme proteins. Textural studies using Instron compression tests on tuna steaks did not indicate significant differences (p > 0.05) between the CO or FS treatments compared with untreated controls. Water-holding studies (expressible moisture and drip loss) also did not show significant differences (p > 0.05) between CO- or FS-treated tuna compared with untreated controls. Freezing and thawing and subsequent cold storage did however lead to significant (p < 0.01) losses of water for all treatments. Muscle protein solubility tests, on the other hand, indicated that FS, 18% CO, and 100% CO-treated tuna steaks had proteins with higher salt solubility compared with untreated controls. This suggests that such treatments may stabilize muscle proteins, which was not apparent from textural and water-holding capacity studies.

Anaerobic Digestion for Reduction and Stabilization of Organic Solid Wastes During Space Missions: Laboratory Studies

The technical feasibility of applying anaerobic digestion for reduction and stabilization of the organic fraction of solid wastes generated during space missions was investigated. This process has the advantages of not requiring oxygen or high temperature and pressure while producing methane, carbon dioxide, nutrients, and compost as valuable products. High-solids leachbed anaerobic digestion employed here involves a solidphase fermentation with leachate recycle between new and old reactors for inoculation, wetting, and removal of volatile organic acids during startup. After anaerobic conversion is complete, the compost bed may be used for biofiltration and plant growth medium. The nutrientrich leachate may also be used as a vehicle for nutrient recycle. Physical properties of representative waste feedstocks were determined to evaluate their space requirements and hydraulic leachability in the selected digester design. Anaerobic biochemical methane potential assays were run on several feedstocks to determine extent and rates of bioconversion. Modifications for operation of a leachbed anaerobic digestion process in space environments were incorporated into a modified design, including flooded operation to force leachate through feedstock beds and separation of biogas from leachate in a gas collection reservoir. The results of runs in a prototype laboratoryscale reactor system operated on simulated solid waste blends are presented.

Measuring and Predicting Head Space Pressure during Retorting of Thermally Processed Foods

UNLABELLED Traditional metal cans and glass jars have been the mainstay in thermally processed canned foods for more than a century, but are now sharing shelf space with increasingly popular flexible pouches and semi-rigid trays. These flexible packages lack the strength of metal cans and glass jars, and need greater control of external retort pressure during processing. Increasing internal package pressure without counter pressure causes volumetric expansion, putting excessive strain on package seals that may lead to serious container deformation and compromised seal integrity. The primary objective of this study was to measure internal pressure build-up within a rigid air-tight container (module) filled with various model food systems undergoing a retort process in which internal product temperature and pressure, along with external retort temperature and pressure, were measured and recorded at the same time. The pressure build-up in the module was compared with the external retort pressure to determine the pressure differential that would cause package distortion in the case of a flexible package system. The secondary objective was to develop mathematical models to predict these pressure profiles in response to known internal temperature and initial and boundary conditions for the case of the very simplest of model food systems (pure water and aqueous saline and sucrose solutions), followed by food systems of increasing compositional complexity (green beans in water and sweet peas in water). Results showed that error between measured and predicted pressures ranged from 2% to 4% for water, saline, and green beans, and 7% to 13% for sucrose solution and sweet peas. PRACTICAL APPLICATION   Flexible packages have limited strength, and need more accurate and closer control of retort pressure during processing. The package becomes more flexible as it heats and might expand with increasing internal pressure that may cause serious deformation or rupture if not properly controlled and/or counterbalanced with external retort pressure. This article describes methods for determining exactly what the retort pressure profile will need to be to avoid this problem during retorting, and mathematical models to predict these pressures in response to known internal temperature and initial/boundary conditions.

BIODEGRADATION OF TREATED POLYLACTIC ACID (PLA) UNDER ANAEROBIC CONDITIONS

Biodegradation of untreated and treated thermoformed polymer polylactic acid (PLA) under anaerobic conditions was investigated. Treatments consisted of subjecting PLA to irradiation (gamma source and e-beam) and steam (120°C for 3 h). Absorbed doses were 72 and 172 kGy for gamma-irradiated samples and 72, 144, and 216 kGy for e-beam irradiated samples. Methods to assess biodegradation were weight loss of irradiated PLA and biochemical methane potential (BMP) of steam-treated PLA during anaerobic digestion at mesophilic (37°C) and thermophilic (58°C) conditions. Untreated PLA degraded only at thermophilic conditions. Treated PLA degraded at both conditions and was more sensitive to biodegradation, showing greater weight loss and methane yield. The order of effectiveness of treatments from greatest to lowest was steam exposure, gamma irradiation, and e-beam irradiation. Under thermophilic conditions, gamma-irradiated PLA lost 45% of its weight in 180 days, and steam-treated PLA produced methane at 225 cc CH4 per gram in 56 days. The most significant finding of this work is that PLA degrades under anaerobic thermophilic conditions, suggesting that post-consumer PLA material may be used in anaerobic digestion for energy recovery, instead of being treated as waste disposal.

Infrared and Raman studies on polylactide acid and polyethylene glycol-400 blend

As a biodegradableplastic, polylactideacid (PLA) can be blended with polyethylene glycol (PEG) to form a polymer blend because PEG has a good miscibility with PLA. Furthermore, this paper study the functional groups of PLA-PEG400 blend using direct casting to produce matrix film. Fourier Transform Infrared (FTIR) and Raman spectroscopy was used to identify alteration of functional group PLA-PEG400 blend. Absorbance and frequency wavenumber were used to observe any changing among functional group. In general, PLA-PEG blend did not produce a new configuration or chemical properties although some functional groups tended to decrease. PLA-PEG400 film spectra showed a similaritycompared to those of neat PLA because of each pristine polymer. However, FTIR and Raman investigated reducing carbonyl group of PLA with PEG400 addition and followed improving CH-COC bonding. Methyl group represented CH3symmetricchanged both the shift and absorbance.FTIR and Raman spectroscopy observed increasing hydrogen bonding with i...

Influence of sample preparation and instrument settings on hot tack measurements of thin sealant films

Sample preparation can greatly influence the results of laboratory testing of packaging sealant materials. Factors such as test strip width, edge uniformity, sealing die temperature, and die pressure were considered as variables to be considered in the measurement of hot tack. A design of experiment approach was used to explore the rank importance of these factors and any interactive effects that may occur. A commercially used structure – ethylene vinyl acetate (EVA) sealant on a high density polyethylene (HDPE) film – was used for these tests. Experimental results indicated that sample width, die temperature, and die pressure were the most influential factors. Edge effects, namely a regular sine wave pattern and a random irregular edge had little influence on hot tack results and there were no significant interactive effects noted.

Cryoconcentration of flavonoid extract for enhanced biophotovoltaics and pH sensitive thin films

Flavonoids are important value added products for dye sensitized solar cells biosensors, functional foods, medicinal supplements, nanomaterial synthesis, and other applications. Brassica oleracea contains high levels of anthocyanins in leaf sap vacuoles, and there are many viable extraction techniques that vary in terms of simplicity, environmental impact, cost, and extract photochemical/electrochemical properties. The efficiency of value added biotechnologies from flavonoid is a function of anthocyanin activity/concentration and molecule stability (i.e., ability to retain molecular resonance under a wide range of conditions). In this paper, we show that block cryoconcentration and partial thawing of anthocyanin from B. oleracea is a green, facile, and highly efficient technique that does not require any special equipment or protocols for producing enhanced value added products. Cryoconcentration increased anthocyanin activity and total phenol content approximately 10 times compared with common extraction techniques. Cryoconcentrated extract had enhanced electrochemical properties (higher oxidation potential), improved chroma, and higher UV absorbance than extract produced with other methods for a pH range of 2–12, with minimal effect on the diffusion coefficient of the extract. As a proof of concept for energy harvesting and sensor applications, dye sensitized solar cells and pH‐sensitive thin films were prepared and tested. These devices were comparable with other recently published biotechnologies in terms of efficacy, but did not require expensive/environmentally detrimental extraction or concentration methods. This low cost, biorenewable, and simple method can be used for development of a variety of value added products.

Steam treatment of waste Polylactid acid (PLA) based products for lactic acid recovery

possible at the temperatures used here. A maximum recovery (yield) of lactic acid of 35% was obtained at a loading of 7.5 g, temperature at 121 °C and exposure time of 720 min. At 160°C , recovery was 25% but obtained within 120 minutes. Results suggest that PLA-product waste behaviour will differ from pure PLA pellet. With PLA-product waste complete lactic acid recovery was not possible and other by-products like acetic and propionic acids were produced from thermal treatment.