General approach to measurements of meat and meat products 1. Sampling 2. Analytical methods

Sampling - –Composite sample consisting of several sub-samples –Combine sub-samples (slices, links, packages, scoops, handfulls, etc.) ---grind, mix, blend --- take test samples in duplicate or triplicate for analyses. Calculate mean or average of the test samples for product value. BUT… how many sub-samples are needed?

Number of sub-samples –Determined by variation among the sub- samples –Need to know variance or standard deviation –Standard deviation essentially tells the range of values

 1 std. Dev. = 67 % of values in a normal distribution  2 s = 95 %  3 s = 99 % Therefore 6 s = full range

Determining the number of sub-samples needed n = number of sub-samples s = standard deviation of sub-samples E = error tolerated n = 3 s 2 E

Example: s = 1 % E = 1 % n = 3 x 1 2 = 9 sub-samples 1

More variability in sub-samples s = 2 % E = 1 % n = 3 x 2 2 = 36 sub-samples 1

More accuracy (less error) desired s = 1 % E = 0.5 % n = 3 x 1 = 36 sub-samples 0.5

Preparation of sub-samples to form composite Sources: 1. American Society for Testing and Materials (ASTM) 2. AOAC International previously known as - Association of Official Analytical Chemists 3. USDA – Meat and Poultry

Recommended procedures for sample prep. of meat and poultry products –AOAC 1. meat grinder with 1/8 inch plate / mix 3-5 times –dependent on product 2. bowl cutter –chill all parts before use 3. Small food choppers with enclosed bowls (cuisinart, Robot Coupe) –4 - 30s bursts with scraping the bowl between each –USDA –grind 3 times with 1/8 inch plate or smaller –beware fat smearing, water evaporation

Sample prep - laboratory –Liquid nitrogen / Waring Blender ultimate in uniformity excellent for research samples especially if stored frozen beware rapid thawing and evaporation

Analytical methods –Two choices …. a. Official methods evaluated and endorsed by AOAC International and others (American Society for Testing and Materials, American Oil Chemists Society, etc.) accurate and precise but often tedious and time consuming necessary for USDA accredited laboratories

Analytical methods (continued) b. Rapid methods quick and easy, often not as accurate or precise

Methods evaluation –Repeatability standard deviation of measurements done on the same sample by the same individual / laboratory –Reproducibility standard deviation of measurements done on the same sample by different individuals / laboratories –Bias constant high / low values