AOAC 133rd Annual Meeting - Final Program

Scientific Sessions | Wednesday

measurement of the glucose or galactose released. In the case of the matrix described above for “lactose free” products, the selectivity of the β -galactosidase employed is of paramount importance. Unselective hydrolysis of the lactose analogues present leads to additional glucose/galactose formation and a resulting overestimation of lactose content. In this presentation, a highly selective, quantitative method for the measurement of lactose in “lactose-free” products will be described with specific focus on the identification of the β -galactosidase with the required selectivity. 3:45 PM Measurement of Fructan (inulin, levan, and branched) in Foods, Feeds and Agricultural Products Lucie Charmier, Barry McCleary, Megazyme All fructans, include inulin, levan, and agave (branched) are quantitatively hydrolysed to fructose and glucose by a combi- nation of exo-inulinase, endo-inulinase and endo-levanase. endo-Acting enzymes are required for rapid hydrolysis of higher degree of polymerization fructans. Complete hydrolysis to monosaccharides requires the action of exo-inulinase. Enzymes preparations must be devoid of activities on β -glucan and starch. Released fructose and glucose is measured either chemically (PAHBAH reagent) or enzymatically. If determined chemically, starch must first be removed as this is partially hydrolyzed by the highly alkaline PAHBAH reagent, resulting in overestimation. exo-Inulinase also hydrolyses sucrose, consequently sucrose must be removed from the sample solution before fructan hydro- lysis. This is achieved by hydrolysis with a specific sucrase (which has no action on fructan). Starch is hydrolyzed to glucose by a mixture of highly purified b-amylase, pullulanase and maltase and galactosyl-sucrose oligosaccharides (e.g., raffinose) are hydrolyzed by hydrolysis with α -galactosidase. All reducing sugars are “removed” by reduction to their corresponding sugar alcohols with sodium borohydride, allowing specific hydrolysis and measurement of fructan. This procedure is quantitative for all native (non-reducing) fructans. In this presentation, a method for measurement of fructan in foods, animal feeds and pet foods (AOAC Method 2018.07) will be described. 4:00 PM Challenges in the Specific Measurement of α - and β -glucans in Natural Products and Ingredients Barry McCleary, Ciara McLoughlin, Lucie Charmier, Megazyme Starch is generally determined enzymatically using heat-stable α -amylase and amyloglucosidase. More recently, a thermo- stable α -amylase, both stable and active at pH 5 at ~ 100 o C has been employed. Maltose, maltodextrins, phytoglycogen, and

glycogen are also quantitatively hydrolyzed to glucose. How “starch” is defined determines what pre-treatments are required to remove dextrins. Resistant starch (RS) must first be dissolved before enzymatic hydrolysis can occur. For most RS, dissolution of the starch in DMSO, NaOH or KOH (with neutralization) is effective. Measurement of the starch content of phosphate cross- linked is more challenging. Incubation in NaOH for 30 min at 50 o C, followed by hydrolysis with α -amylase at 100 o C for 30 min and then Amyloglucosidase at 50 o C is effective (McCleary et al., unpublished). β -Glucan encompasses a range of polysac- charides including cereal β -glucan (1,3:1,4-linked), yeast and mushroom β -glucan (1,3- and 1,6-linked) and cellulose (1,4- linked). Cereal β -glucan is specifically hydrolyzed to glucose by lichenase plus β -glucosidase. Yeast β -glucan can be effectively hydrolyzed to glucose by a mixture of exo- and endo-1,3- β - glucanases. However, measurement of fungal β -glucan requires the use of strong acids along with enzymatic methods. Methods for the measurement of starch, resistant starch, cereal, yeast and mushroom β -glucans will be presented and discussed. 4:15 PM Development of an Enzyme-Chemometric Method to Replace Rat Digestibility for PDCAAS Any food product making a protein claim must provide a percent daily value of quality protein on its nutrition facts panel. Quality protein is required to be determined by multiplying the amount of crude protein by the Protein Digestibility Corrected Amino Acid Score (PDCAAS) value. The PDCAAS value is comprised of the lowest essential amino acid value ratio relative to a complete protein for human growth multiplied by a digestibil- ity factor which is determined by a rat feeding study. There is a need in the food industry for an ethical, non-animal-based method which can determine protein digestibility for lawful protein labeling. This presentation focuses on the development of a new in vitro enzymatic-digestibility method called the ASAP- Quality method targeted to replace the current rat digestibility model used for PDCAAS. A high correlation of the ASAP-Quality method to the rat digestibility model was achieved through determining and controlling proper pH, temperature, time and enzyme/substrate ratios for a multi-protease system and utilizing a chemometric relationship of the digest end-point measurement to that of the rat digestion end-point measurement. The chemom- etric relationship was refined through parallel measurements of ingredients and food products with both the ASAP-Quality and Rat-PDCAAS methods. Determinations of Protein Quality David Plank, WRSS Food & Nutrition Insights

32 SEPTEMBER 6–12, 2019 SHERATON DENVER DOWNTOWN HOTEL