Interplay between transglutaminase treatment and changes in digestibility of dietary proteins.

The changes in digestibility of TG-treated myofibrillar protein (MP), soybean protein isolate (SPI) and mixed proteins were evaluated by measuring liberation of primary amino groups, monitoring structural changes and investigating peptide fingerprints. TG treatment generally increased gastric digestion of treated proteins, possibly due to the structural changes occurred during TG treatment. In contrast, the initial intestinal digestion was suppressed by TG treatment. Compared with MP, the digestibility and peptide composition of SPI were affected by TG treatment to a larger degree, possibly due to the higher level of glutamine in SPI. Peptidomics analysis indicated that the changes in peptide composition of digests of TG-treated samples were related with the loss of Lys residues during TG treatment. Larger quantities of bioactive peptides KIEFEQFLPM, EVHEPEEKPRPK and TVKEDQVFPMNPPK were released after digestion of TG-treated MP. These results highlighted the complex and substantial influence of TG treatment on the digestibility of dietary proteins.

Effect of storage, food processing and novel extraction technologies on onions flavonoid content: A review.

Onions play an important part in the daily diet for most populations around the world owing to their nutritional composition and their unique capacity to naturally flavor dishes. Onions contain quercetin and its derivatives - the predominant flavonoid in onions that exert a great contribution to the effective bioactive properties of onion, including its derived products. The present paper comprehensively reviewed flavonoids (with a specific focus on quercetin in onions): their chemical composition, distribution, bioactivities in onion, and impacting factors with a focus on how they can be affected by various post-harvest conditions (storage and food processing). In addition, research on the extraction of flavonoid compounds from onions using a number of novel technologies was also reviewed.

Peptidomic Investigation of the Interplay between Enzymatic Tenderization and the Digestibility of Beef Semimembranosus Proteins.

This work investigated the influence of enzymatic tenderization on digestibility changes of beef semimembranosus proteins using peptidomics methods. Hydrolysis by proteinase K and bromelain elevated the average bitterness index of identified peptides by generating high-Q values peptides (1714-1790 Cal/mol), including KDLFDPIIQ, LIDDHFLFDKPVSPL, and QLIDDHFLFDKPVSPLLL. Proteolysis during enzymatic tenderization acted as a "pre-digestion" step and significantly elevated the degree of hydrolysis of beef protein (by 4.5-17.3%) in subsequent simulated gastrointestinal digestion. Peptidomics analysis of digests revealed large variations in the peptide composition, which was positively correlated with the degree of proteolysis during enzymatic tenderization. Enzymatic tenderization with proteinase K- (for 0.5 h) or bromelain-treated samples largely increased the survival rate (by 65.5 or 82.8%) of peptides during simulated digestion, possibly because of the "secondary enzyme-substrate interaction" effect. This work could provide a new sight into the possible influence of enzymatic tenderization on meat nutrition.

High internal phase emulsions stabilized with amyloid fibrils and their polysaccharide complexes for encapsulation and protection of ß-carotene.

In present study, lysozyme amyloid fibrils and their complexes with polysaccharides were investigated for stabilizing high internal phase emulsions (HIPEs). Linear polysaccharides, alginate and λ-carrageenan and branching ones, low and high methyl esterified pectins electrostatically bind to amyloid fibrils in nematic phase, forming well dispersed coacervates showing birefringence under polarized light. Comparatively, the polysaccharides associate with the globule protein monomers, leading to the precipitated coacervate. Interaction with the polysaccharides enhances the strength of the amyloid fibrils network. After converting protein monomers to amyloid fibrils, the binding between polysaccharides and the proteins is significantly enhanced with the affinity constant (KD) from sub-nmol to pmol level. For the first time, amyloid fibrils are found to stabilize HIPEs with highly packed polyhedral geometries in microstructure, which is dependent on protein concentration and volume fraction of the internal oil phase. The HIPEs stabilized with the amyloid fibril-polysaccharide complexes are stronger than those stabilized with only amyloid fibrils, which is attributed to the increase in the modulus of the disperse phase. The HIPE systems can encapsulate and stabilize ß-carotene against ultraviolet irradiation, thermal treatment and iron ions in aqueous phase, which is mainly attributed to the protection effects of the interfacial lysozyme amyloid fibril membrane.

Possibilities for developing texture-modified beef steaks suitable for older consumers using fruit-derived proteolytic enzymes.

Meat intakes in the older population are commonly reduced because the relatively tough texture of meat can impair mastication. Fruit-derived proteolytic enzymes have been reported to have beneficial effects on tenderness, by causing significant degradation of myofibrillar proteins and collagen. Three treatments including: papain, bromelain, and a 50:50 mixture of papain/bromelain, alongside one control were applied to beef M. semitendinosus steaks. Effects on Warner-Bratzler shear force, texture parameters, color, and cook loss were determined. Both enzymatic treatments that included papain significantly reduced Warner-Bratzler shear force values (p < .05) and increased cook loss. Beef steaks tenderized with papain and papain/bromelain offer potential for inclusion in older consumers' diets, but improvement in tenderization may be associated with a reduction in processing yield. PRACTICAL APPLICATIONS: Meat processors have a role to play in enhancing the availability of appropriate foodstuffs for older people, through developing targeted products that will meet the specialized nutritional and chemosensory needs of this cohort. Meat intakes in the older population are commonly reduced because the relatively tough texture of meat can impair mastication. In this study, beef steaks tenderized with papain and papain: bromelain (50:50) were demonstrated to produce more tender meat products, with a lower cook loss compared with tenderization with bromelain alone, which has relevance to the development of texture-optimized meat products that appeal to older adults with difficulty in mastication. This information could help meat processors to develop strategies for optimization of texture-modified beef products within their own businesses.