Darrell W. Donahue

Methods for rapid separation and concentration of bacteria in food that bypass time-consuming cultural enrichment.

The rapid detection of pathogenic organisms that cause foodborne illnesses is needed to insure food safety. Conventional methods for the detection of pathogens in foods are time-consuming and labor-intensive. New advanced rapid methods (i.e., polymerase chain reaction, DNA probes) are more sensitive and selective than conventional techniques, but many of these tests are inhibited by food components, rendering them dependent on slow cultural enrichment. The need for alternative methods that will rapidly separate and concentrate bacteria directly from food samples, thereby reducing the time required for these new rapid detection techniques, is evident. Separation and concentration methods extract target bacteria from interfering food components and/or concentrate bacteria to detectable levels. This review describes several methods used to separate and/or concentrate bacteria in food samples. Several methods discussed here, including centrifugation and immunomagnetic separation, have been successfully used, individually and in combination, to rapidly separate and/or concentrate bacteria from food samples in less time than is required for cultural enrichment.

Comparison of three near infrared spectrophotometers for infestation detection in wild blueberries using multivariate calibration models

A near infrared (NIR) spectroscopy system for rapid, automated and non-destructive detection of insect infestation in blueberries is desirable to ensure high quality fruit for the fresh and processed markets. The selection of suitable instruments is the first step in system development. Three diode array spectrophotometers were evaluated based on technical specifications and capacity for larva detection in wild blueberries (Vaccinium angustifolium) using discriminant partial least squares (PLS) regression models. These instruments, differing mainly in wavelength range and detector type, comprised two spectrophotometers with scanning wavelength ranges of 650–1100 nm and 600–1700 nm and an imaging spectrograph with the scanning range of 950–1400 nm. The assessed factors affecting predictions included signal-to-noise ratio, wavelength range, resolution, measurement configuration, spectral pre-processing and absorbance bands related to infestation. The scanning spectrophotometers demonstrated higher signal-to-noise ratios with infestation prediction accuracies of 82% and 76.9% compared to the imaging spectrograph with 58.9% accuracy. Resolution, spectral pre-processing and measurement configuration had a lesser effect on model accuracy than wavelength range. The 950–1690 nm bands were identified as important for infestation prediction. In general, NIR spectroscopy should be a feasible technique for rapid classification of insect infestation in fruit.

Implementing an interdisciplinary marketing/engineering course project: Project format, preliminary evaluation, and critical factor review

This article reports on an innovative product development class project in which marketing and bio-resource engineering students work together. The project modifies a project suggested by Lunsford and Henshaw employing marketing and engineering students. The project is executed as a professional development activity designed to give students a broader perspective on their discipline as well as model the types of work teams they will experience on the job. This article describes the approach to the project used by the interdisciplinary team of instructors, the faculty and the students™ responses to the project, and suggested improvements for further implementations.

Evaluation of In-vessel Composting of University Postconsumer Food Wastes

A prototype in-vessel composting unit, which includes air circulation and misting systems, was designed and built as a senior capstone project at the Bio-Resource Engineering Department at the University of Maine. The university Office of Resource Conservation and Recovery initiated a recycling program for postconsumer food waste generated by the residence hall commons areas in 1991. This food waste is composted using the traditional methods of windrow composting and experiences vermin and odor problems.The prototype in-vessel system was evaluated to determine if it reduced the environmental challenges presented by vermin and odor control. Various mixtures of food waste and bulking agents were tried ranging from 1:4 (food waste:bulking agent) to 1:1. Results show that if the food waste is composted in the in-vessel system for at least 14 days, before being windrowed, the vermin and odor problems are reduced. Computer controlled temperature, humidity, oxygen, and carbon dioxide monitoring equipment were ev...

Intermittent Aeration for In-vessel Composting Of Crab Processing Waste

A crab processing waste/wood shaving mixture was composted in-vessel with four intermittent aeration strategies. The composting process was monitored to assess the efficacy of the aeration methods. Temperature, moisture content and volatile solids of the compost were monitored along with the interstitial oxygen concentration. There was no significant difference in temperature profiles between constant frequency aeration and temperature feedback controlled aeration methods. An increased frequency of aeration resulted in significantly more drying than the less frequent aeration using the same total air volume. Results indicated that air volume could be reduced after the first five days of composting, and the in-vessel composting retention time could be reduced to 15 to 17 days for odor and vermin/vector problems prevention.

Modelling Beauveria bassiana horizontal transmission

1 We modelled horizontal transmission of Beauveria bassiana in Colorado potato beetle (CPB) between larval cadavers and soil inhabiting prepupae.

Consumer and instrumental evaluation of Maine wild blueberries for the fresh pack market

Abstract Maine wild blueberries prepared for the fresh pack market compete with cultivated blueberries for market share. In an effort to increase market share, Maine producers are seeking an understanding of consumer preference and how it relates to objective blueberry quality measures. Consumer and instrumental measurements were evaluated over a 3-year period from 1996 to 1998. Freshly harvested blueberries were sized according to diameter; 6–8, 9–10 and 11–12 mm. A consumer panel, recruited from the university and surrounding communities, ranged in age from 18 to 62 and was geographically and gender diverse. The panel was presented the various size classes of blueberries monadically in balanced random order and asked to rate the samples on a nine-point hedonic scale. Quasi-static compression measurements of firmness were paired with these individual sensory measurements. Statistical regression models and back propagation neural networks were used to determine and predict consumer response from the instrumental response. There seemed to be a compression of the consumer data to the upper end of the hedonic scale. Year and time of season were significant for the overall consumer response and the force and firmness instrumental measurements. Berry size was significant with respect to all sensory and instrumental measurements. The results of the overall sensory and instrumental evaluation revealed that size class 9–10 mm was the ideal size for fresh market selection, however, panelists preferred the large (11–12 mm) berries in visual acceptance evaluations. The statistical regression analysis revealed no linear relationships except for the size class 9–10 mm, where positive linear relationships were found between sensory and instrumental measurements. The neural networks were poor predictors of the sensory data based on the instrumental data. These findings highlight the difficulties in characterizing consumer preference with instrumental and hedonic measurements.

An Expert System for Diagnosing Diseases of Tobacco

An expert system to diagnose flue-cured tobacco diseases was developed with the help of two plant pathologists. The significant points of interaction between the knowledge engineer and the domain experts are highlighted. Interaction with field experts and growers is discussed as a vehicle to make the expert system more widely adopted.

FORCED AIR REMOVAL OF SURFACE MOISTURE FROM MAINE WILD BLUEBERRIES FOR THE FRESH PACK MARKET

Field moisture in the form of early-morning or late-evening dew significantly reduces the quality of Maine wild blueberries. Most fresh pack producers are part-time producers, governed by outside employment, and must harvest during times when the dew is the heaviest. A prototype dryer was designed, allowing for continual flow and ambient air blowers in series, to remove excess water from the blueberries. Tests were performed three times during the 1997 growing season (early, mid, and late season) to evaluate the moisture removal capacity of the prototype dryer, while not further increasing processing damage. Weight loss, anthocyanin leakage test and compressive force measurements were used as indicators of satisfactory operation. These indicators proved that the quality of harvestable, ripe Maine wild blueberries decreased as the length of time in field increased. Results indicate adequate moisture removal (about one percent by mass) with no significant increase in processing damage.

Simulation of alternative agricultural marketing systems

Abstract A study of the current US flue-cured 2 tobacco marketing system was performed to determine the need for a new system. Computer simulation models of 13 alternative marketing systems were developed. The throughput, kg of tobacco processed in a 40-hour period, was measured. Maximum throughput predicted by the 13 models varied from 298 508 kg to 1 347 472 kg per 40-hour period. A fractional factorial experimental design was used to determine significant model factors. Statistical models were employed to isolate important factors and differences among the marketing systems studied. Two marketing systems are recommended to the US flue-cured tobacco industry for further analysis.