Evaluation of Differential Scanning Calorimetry as a Potential Methodology to Assess Starch Gelatinization in Commercial Poultry Diets Thermally Processed under Multiple Retention Time and Temperature Combinations

Abstract

Starch is known to gelatinize in the presence of heat and water during thermal processing; thus, causing the unraveling of the starch granule. The occurrence of starch gelatinization in diets having high inclusions of carbohydrates during thermal processing has been suggested to improve energy digestibility in production animals such as swine and poultry. Experiments were conducted to assess starch gelatinization (SG) and total starch (TS) content in multi-component animal food using Differential Scanning Calorimetry (DSC) and Association of Official Analytical Chemists (AOAC) 996.11 methodologies, respectively. DSC was utilized to assess SG in cooked and uncooked corn starch (CS), cooked and uncooked ground corn, uncooked meal, and pelleted animal food when set to a conclusion temperature of either 160 or 200 C. Enthalpy (H1) differed among cooked starch sources (P = 0.0080) and DSC temperature (P = 0.0429). No significant interaction was observed between starch source and DSC temperature (P = 0.2166) for cooked samples. Calculated DG of CS was 71.3 %, while the DG for GC and pelleted animal food could not be calculated because the uncooked enthalpy (H0) for both starch sources was greater than the cooked enthalpy (H1). Nine treatment combinations were analyzed with 3 conditioning temperatures (CT; 75, 85, and 95 °C) and 3 retention times (RT) in the Hygieniser (80, 160, and 240 s); samples (n = 198) for DSC analysis of SG were collected on 3 separate d. Data for all experiments were analyzed using the GLIMMIX procedure of SAS (V 9.4) and all means were separated utilizing the PDIFF option of SAS. Means were declared significantly different at P = 0.05. Post- conditioner samples conditioned at 75 °C had higher enthalpy (P = 0.0182) than samples conditioned at 85 and 95 °C. Enthalpy of samples collected after the Hygieniser and conditioned at 75 °C were higher (P = 0.0486) than samples conditioned at 85 °C. An interaction (P = 0.0200) was observed for the enthalpy of samples collected after pelleting and conditioned at 75 °C and retained in the Hygieniser for 80 s having the greatest enthalpy (54.9 J/g) than all other CT and RT combinations. The combination of proteins, fats, and other carbohydrate fractions do not appear to allow for the use of DSC. Based on these results, DSC is not a suitable method to assess SG in multi-component animal food. AOAC 996.11 was utilized to assess TS in multi-component animal food using 9 treatment combinations with 3 CT and 3 RT. Conditioning temperature had the greatest effect on TS content of samples collected after the conditioner at 95 C compared to 75 and 85 C (P = 0.0002). Samples collected after the Hygieniser and conditioned at 75 C had the highest amount of TS compared to 85 and 95 C (P = 0.0001). The pelleted samples had the highest percentage of TS (P = 0.0152) at 160 s, but the samples obtained after the Hygieniser had the highest TS percentage when retained for 80 s (P = 0.9339). A significant interaction was observed between CT and RT in relation to TS content (%) for the after pelleted samples (P =0.0034). No differences were observed between CT and RT for the TS content of the after Hygieniser samples (P = 0.853). The highest percentage of TS occurred in the Hygieniser at 85 C for 240 s. AOAC 996.11 is only utilized to assess the percentage of TS present in a sample. To further determine the amount of SG that occurred in this diet using 9 treatment combination with 3 CT and 3 RT, the glucoamylase method must be utilized.