Microwave Irradiation Induced Changes in Protein Molecular Structures of Barley Grains: Relationship to Changes in Protein Chemical Profile, Protein Subfractions, and Digestion in Dairy Cows

Abstract

The objectives of this study were to evaluate microwave irradiation (MIR) induced changes in crude protein (CP) subfraction profiles, ruminal CP degradation characteristics and intestinal digestibility of rumen undegraded protein (RUP), and protein molecular structures in barley (Hordeum vulgare) grains. Samples from hulled (n = 1) and hulless cultivars (n = 2) of barley, harvested from four replicate plots in two consecutive years, were evaluated. The samples were either kept as raw or irradiated in a microwave for 3 min (MIR3) or 5 min (MIR5). Compared to raw grains, MIR5 decreased the contents of rapidly degradable CP subfraction (from 45.22 to 6.36% CP) and the ruminal degradation rate (from 8.16 to 3.53%/h) of potentially degradable subfraction. As a consequence, the effective ruminal degradability of CP decreased (from 55.70 to 34.08% CP) and RUP supply (from 43.31 to 65.92% CP) to the postruminal tract increased. The MIR decreased the spectral intensities of amide 1, amide II, α-helix, and β-sheet and increased their ratios. The changes in protein spectral intensities were strongly correlated with the changes in CP subfractions and digestive kinetics. These results show that MIR for a short period (5 min) with a lower energy input can improve the nutritive value and utilization of CP in barely grains.

Effects of canola meal pellet conditioning temperature and time on ruminal and intestinal digestion, hourly effective degradation ratio, and potential nitrogen to energy synchronization in dairy cows

“…Heat processing alters EDDM of protein feeds by altering the protein molecular structures, such as the uncoiling of pleated structures or denaturation of the whole protein molecules. These heat-induced structural changes expose the intact AA, and subsequently results in the development of cross-linkages among peptides/AA, and between AA and carbohydrates (Yan et al, 2014). Both temperature and duration of heating play a key role in the level of denaturation and development of cross linkages, and hence the protection of feed against rumen degradation (Khan et al, 2015).…”

Effects of microwave processing conditions on microbial safety and antimicrobial proteins in bovine milk

“…The use of heat exchangers in continuous conventional systems has been shown to lead to minimum damage on the nutritional components in milk when mild temperatures are used (e.g., HTST), in comparison with a batch system. In addition, the use of microwaves, for example, was shown to change protein conformation and cross‐linkages between amino acids and reducing sugars such as during Maillard reactions in a time–temperature‐dependent manner (de Pomerai et al, ; Yan, Khan, Zhang, Yang, & Yu, ). In summary, the type of heating system (i.e., continuous heat exchanger, batch system, or incidence of microwaves) has a key impact on the preservation of milk antimicrobial proteins.…”

The inter‐relationship between processing‐induced molecular structure features and metabolic and digestive characteristics in hulled and hulless barley (Hordeum vulgare) grains with altered carbohydrate traits

“…In our previous study, sample preparation was reported as: Grains from two newly‐developed hulless cultivars ( CDC‐Fibar and HB08302 ) with an altered carbohydrate composition (amylose/amylopectin ratio in β‐glucan) and a normal hulled cultivar (CDC Copeland ) of barley were evaluated. The samples were provided by Aaron D. Beattie (Crop Development Center, University of Saskatchewan, Saskatoon, Canada).…”

“…A previous study has reported that barley is primarily used as an energy source in dairy cow rations. However, hulless barley rapidly and extensively degrades in the rumen, resulting in a lower rumen undegraded protein value .…”

“…The previous study found that MIR decreased the spectral intensities of amide I, amide II, α‐helix and β‐sheet, and increased their ratios compared to raw grains . However, it is not known whether these changes in protein structural spectral intensities are correlated with the changes in true protein nutrient supply in ruminant livestock systems.…”