A.A. Teixeira

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.

Commercially Sterilized Mussel Meats (Mytilus chilensis): A Study on Process Yield

The processing steps most responsible for yield loss in the manufacture of canned mussel meats are the thermal treatments of precooking to remove meats from shells, and thermal processing (retorting) to render the final canned product commercially sterile for long-term shelf stability. The objective of this study was to investigate and evaluate the impact of different combinations of process variables on the ultimate drained weight in the final mussel product (Mytilu chilensis), while verifying that any differences found were statistically and economically significant. The process variables selected for this study were precooking time, brine salt concentration, and retort temperature. Results indicated 2 combinations of process variables producing the widest difference in final drained weight, designated best combination and worst combination with 35% and 29% yield, respectively. Significance of this difference was determined by employing a Bootstrap methodology, which assumes an empirical distribution of statistical error. A difference of nearly 6 percentage points in total yield was found. This represents a 20% increase in annual sales from the same quantity of raw material, in addition to increase in yield, the conditions for the best process included a retort process time 65% shorter than that for the worst process, this difference in yield could have significant economic impact, important to the mussel canning industry.

Simple, practical, and efficient on-line correction of process deviations in batch retort through simulation

Abstract This paper describes a simple, practical and efficient (nearly precise, yet safe) strategy for on-line correction of thermal process deviations during retort sterilization of canned foods. The strategy is intended for easy implementation in any cannery around the world. Commercial systems currently in use for on-line correction of process deviations do so by extending process time to that which would be needed had the entire process been carried out at the lower retort temperature reached at the lowest point in the deviation (“commercial” correction). This method of correction often results in extensive unnecessary over-processing with concomitant deterioration in product quality, and costly interruption to the retort loading/unloading rotation schedules in retort cook room operations. These problems are addressed by a novel control strategy that takes into account the duration of the deviation in addition to the magnitude of the temperature drop. It calculates a “proportional” extended process time at the recovered retort temperature that will deliver the final specified target lethality with very little over processing in comparison to current industry practice. Results from an exhaustive “optimization” search routine using the complex method are also reported, that show the proposed strategy will always result in a corrected process that delivers no less than the final target lethality specified for the originally scheduled process.

Ohmic Thawing of Shrimp Blocks

Conventional water immersion thawing of frozen seafood blocks requires large amounts of water, causes cross-contamination problems, and loss of solids to leaching. Frozen shrimp blocks and fish were thawed by passing an alternating current through the blocks. 60 Hz and up to 480 V were used. An automated amps and voltage data acquisition system was developed. A changing current regime was used to prevent local overheating. Thawing times for different blocks for different current-voltage regimes are presented. A preliminary economic analysis and sensory tests were performed.

Automatic control of batch thermal processing of canned foods

Abstract: This chapter describes theoretical, practical and efficient strategies for on-line correction of thermal process deviations during retort sterilization of canned foods. It presents a review of recent developments over the past 10xa0years that have further advanced the state of the art in improving food safety, quality and manufacturing efficiency in the canned food industry worldwide. The focus is on retort control systems, and the various approaches that have been taken to help canned food processors accomplish on-line correction of unexpected process deviations, the major cause of lost productivity. Important features of each approach are discussed, along with suggested industry applications that would be appropriate for each method. The chapter concludes with a discussion of future trends to be expected in the industry.