Quantification of nitrogen in the liquid fraction and in vitro assessment of lysine bioavailability in the solid fraction of soybean meal hydrolysates.

Soybean meal (SBM) is a product generated from the manufacture of soybean oil and has the potential for use as a source of fermentable sugars for ethanol production or as a protein source for animal feeds. Knowing the levels of nitrogen available from ammonium is a necessary element of the ethanolic fermentation process while identifying the levels of essential amino acids such as lysine is important in determining usage as a feed source. As such the purpose of this study was to quantify total nitrogen and ammonium in the liquid fraction of hydrolyzed SBM and to evaluate total and bioavailable lysine in the solid fraction of the hydrolyzed SBM. The effects of acid concentration, cellulase and ß-glucosidase on total and ammonium nitrogen were studied with analysis indicating that higher acid concentrations increased nitrogen compounds with ammonium concentrations ranging from 0.20 to 1.24 g L-1 while enzymatic treatments did not significantly increase nitrogen levels. Total and bioavailable lysine was quantified by use of an auxotrophic gfpmut3 E.coli whole-cell bioassay organism incapable of lysine biosynthesis. Acid and enzymatic treatments were applied with lysine bioavailability increasing from a base of 82% for untreated SBM to up to 97%. Our results demonstrated that SBM has the potential to serve in ethanolic fermentation and as an optimal source essential amino acid lysine.

Analysis of microbial diversity on deli slicers using polymerase chain reaction and denaturing gradient gel electrophoresis technologies.

Cross-contamination of pathogenic and spoilage bacteria from food-contact surfaces to food products is a serious public health issue. Bacteria may survive and attach to food-contact surfaces by residual food components and/or background bacteria which may subsequently transfer to other food products. Deli slicers, generally used for slicing ready-to-eat products, can serve as potential sources for considerable bacterial transfer. The objective of this study was to assess the extent and distribution of microbial diversity of deli slicers by identification of pathogenic and background bacteria. Slicer-swab samples were collected from restaurants in Arkansas and Texas in the United States. Ten surface areas for each slicer were swabbed using sterile sponges. Denaturing gradient gel electrophoresis (DGGE) was applied to investigate the fingerprint of samples, and each band was further identified by sequence analysis. Pseudomonads were identified as the dominant bacteria followed by Enterobacteriaceae family, and lactic acid bacteria such as Lactococcus lactis and Streptococcus thermophilus were also found. Bacterial distribution was similar for all surface areas, while the blade guard exhibited the greatest diversity. This study provides a profile of the microbial ecology of slicers using DGGE to develop more specific sanitation practices and to reduce cross-contamination during slicing.

Impact of milling and water-to-rice ratio on cooked rice and wastewater properties.

Due to the environmental concerns and expense associated with the disposal of wastewater after industrial cooking of rice, the purpose of this study was to evaluate the extent of leaching, water uptake and volumetric expansion of rice during cooking at various milling durations and water-to-rice ratios. Two cultivars of Arkansas rice, a long grain (Francis) and a medium grain (Jupiter), were milled for 10, 20, and 30 s with a laboratory mill. Samples were cooked in aluminum foil covered beakers at water-to-rice ratios of 10:1, 15:1, and 20:1. After 20 min, rice was weighed for water uptake and measured for volumetric expansion using hexane displacement. The excess cooking water was evaluated for total solids, amylose, and protein to determine the extent of leaching. Water uptake and volumetric expansion significantly increased with milling duration in both cultivars. Leached solids increased as the water-to-rice ratio increased in Francis and increased with milling duration in Jupiter; however, the amylose content of leached solids was unaffected by the water-to-rice ratio in both cultivars. Thus, shorter milling durations may limit the extent of leaching during cooking, as observed with Jupiter, while a lower water-to-rice ratio may reduce wastewater contamination for cultivars similar to Francis.

Enzymatic hydrolysis of poultry meal with endo- and exopeptidases.

The objective of this research was to determine whether commercial proteases are capable of hydrolyzing denatured poultry by-product proteins that have gone through a rendering process. The material used for this research was low-ash poultry meal obtained from a local poultry processor. Samples of poultry meal were treated with the commercial proteases Alcalase, Flavourzyme, Protamex, and Liquipanol that were added individually or as a combination of 2 proteases, which were incorporated either simultaneously or sequentially. Temperature was controlled during the reaction to the optimal level for each enzyme, and pH was initially adjusted to the most favorable level for each enzyme and was maintained during the course of the reaction by addition of NaOH at established intervals. Consumption of NaOH was used to calculate the degree of hydrolysis. At the end of the hydrolysis, the molecular weight of selected hydrolysates was determined by size exclusion chromatography and by gel electrophoresis. In addition, amino acid analysis was performed on selected hydrolysates. Results show that the sequential treatment with Alcalase and Flavourzyme served best for the preparation of poultry meal hydrolysates with a maximum degree of hydrolysis of 11.1% and the highest hydrolyzable material recovered at 58%, which is attributed to the combined nature of the endo- and exocatalytic action of Alcalase and Flavourzyme, respectively. Hydrolysate with Flavourzyme or the combination of Flavourzyme and Alcalase were both good methods to produce significant amounts of free amino acids. This research shows the feasibility of hydrolyzing poultry by-products that went through a rendering process using different brands of commercial proteases. Findings from this research are important in the preparation of palatants, in which relatively inexpensive hydrolyzed poultry meal could be used to improve the flavor of companion animal food products.

Study of the biosynthesis of 1-octen-3-ol using a crude homogenate of Agaricus bisporus in a bioreactor.

1-Octen-3-ol and 10-oxo-trans-8-decenoic acid are metabolites of the breakdown of linoleic acid (LA) by mushroom enzymes. These compounds can be produced in a bioreactor using a crude mushroom homogenate and the exogenous addition of LA and oxygen. The factors' duration of blending, mushroom-buffer ratio, effect of a surfactant, whole against partially clarified reaction broths, purity of LA, and utilization of stumps instead of whole mushrooms were studied for their effect on reaction yield using a 1-L bioreactor. The results showed the feasibility of using the more inexpensive 60%-pure LA instead of the 99%-pure LA even when a yield loss was involved. Waste stumps could be used instead of whole mushrooms with a yield decline of 26%.