Determining endotoxin content of ground beef by the Limulus amoebocyte lysate test as a rapid indicator of microbial quality

Abstract

Eighty-four samples of ground beef were placed into five half-log cycle groups based upon aerobic plate count (APC) results. Endotoxins were determined by the Limulus amoebocyte lysate test (LAL), and gram-negative viable counts were determined by a violet red bile agar overlay method. Ten samples with a log of APC of less than 5.50 had an APC mean of less than 5.24 and mean endotoxin content by the LAL of 51 ng/g. The 15 samples with APCs between a log of 5.50 and 5.99 had an APC mean of 5.79/g and an endotoxin mean of 103.8 ng/g. Twenty-eight samples had APCs between a log of 6.00 and 6.49 with a mean of 5.28/g and an endotoxin mean of 1106.4 ng/g. The 20 samples with APCs between a log of 6.50 and 7.00 had a mean of 6.77/g and an endotoxin mean of 5067.6 ng/g, while 11 samples had a log of APCs of greater than 7.00 with a mean of 7.53 and an endotoxin mean of 7,472 ng/g. Correlation of half-log cycle mean APC and violet red bile agar counts with mean endotoxin content were both highly significant, indicating that LAL-determined endotoxin content can be used to make a rapid approximation of viable plate counts. Because results can be obtained by LAL in 1 h, the finding of low levels of endotoxins can be taken to indicate low-count meat. The use of additional tests of microbial quality may be necessary when high endotoxin levels are found because the LAL detects both viable and nonviable cells.

Accumulation of Stimulants of Toll‐Like Receptor (TLR)‐2 and TLR4 in Meat Products Stored at 5 °C

“…Finally, the limulus system is insensitive to BLPs, and so cannot be used for their quantification (Erridge and Samani 2009). Despite these limitations, however, the LAL assay has been used previously to demonstrate that the endotoxin content of spoiling meat correlates well with microbial load, a finding supported by the present study (Fallowfield and Patterson 1985; Jay and others 1979). The LAL assay has also been used to estimate the amount of endotoxin present in minced beef stored at refrigeration temperature for 6 d to range from approximately 32 μg/g to approximately 2.5 mg/g (Jay and others 1979; Fallowfield and Patterson 1985).…”

“…An alternative method that has been widely used for the quantification of LPS in foodstuffs is the limulus amoebocyte lysate (LAL) assay (Jay and others 1979; Fallowfield and Patterson 1985). As discussed previously, however (Erridge 2010), the LAL assay was found to be not suitable for quantifying the biological activities of TLR‐stimulants in foodstuffs for a number of reasons.…”

Monitoring the microbial contamination of beef carcass tissue with a rapid chromogenic Limulus amoebocyte lysate endpoint assay

“…This assay, based on the initial research of Levin and Bang (Levin et al 1964) is widely used for testing of medical devices and parenteral solutions. Previously, Jay (1977Jay ( , 1981 and Jay et al (1979) had utilized the Limulus amoebocyte lysate (LAL) test for testing ground beef. This original work demonstrated a high correlation between the LAL result and the microbial quality of the product.…”

Rapid CO2 Evolution Method for Determining Shelf Life of Refrigerated Catfish

“…Pretreatment of samples and costly instruments for monitoring conductance or impedance changes are necessary (Dalgaard et al, 1996). The LAL test can only be applied for the detection of gram negative bacteria and does not distinguish between live or dead organisms (Jay et at., 1979;Sullivan et al, 1983).…”