RESUMO
Wheat-based products are staple foods for over a third of the world's population. However, most wheat-based staple foods are provided with a high water content to maintain naturally chewable mouthfeel, which leads to a short shelf life and limits their distribution and marketing. Understanding the fundamental mechanisms and dynamics that drive the quality deterioration is therefore essential for obtaining alternative technologies for optimal quality and extended shelf life. Here, we provide the basis for the physicochemical, structural, and molecular changes occurring in various wheat products during storage, intending to elucidate the underlying deterioration causes. Generally, more desirable qualities are obtained for fresh wheat products, both in appearance and mouthfeel. During storage, changes in the physicochemical properties, structure, main constituents, and water status contribute to the quality deterioration. Based on these changes, deterioration mechanisms are summarized to provide both theoretical and practical references for the quality regulation of high-moisture wheat-based food.
Assuntos
Triticum/química , Água/análise , Análise de Alimentos , Armazenamento de Alimentos , Humanos , PaladarRESUMO
In this study, the improving effects of green tea powder, soluble tea, and tea polyphenols on the mixing and tensile qualities of dough and texture of tea-enriched noodles, as well as the physico-chemical and structural properties of gluten proteins were progressively investigated. Dough strength and noodle texture were significantly increased by all the three tea products. Tea polyphenols in particular presented the most effective improvement with highest dough stability, resistance, and noodle chewiness. SEM indicated that tea products all induced a more developed gluten network, and polyphenol noodle showed the most continuous and ordered structure. FT-IR and fluorescence spectrum indicated that tea polyphenols promoted an enhancement in α-helix structure and the hydrophobic interactions. Tea polyphenols induced the SH/SS interchange during processing and cooking, and enhanced the water-solids interaction in noodles. AFM results showed that polyphenols induced the polymerization of gluten protein molecular chains, with increased chain height and width.
Assuntos
Polifenóis/química , Chá/química , Triticum/química , Fenômenos Químicos , Culinária , Glutens/química , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
In this study, the inhibiting effects of low-molecular weight polyols on the deterioration of gluten network and noodle texture were systematically investigated, based on dough rheological properties, and the macroscopic, structural and water status changes of gluten protein during storage of fresh noodles. Both glycerol and propylene glycol significantly restrained the decrease of GMP gel weight, LA-SRC value, hardness and springiness, and the increase of cooking loss. SEM showed that polyols retarded the collapse of gluten network, with still continuous gluten fibrils. The inner structure of polyol noodles was much less damaged after 2â¯days, with more uniform moisture distribution in MRI images. Potential dynamic depolymerization and repolymerization interactions were detected for protein components during processing and cooking, which might contribute to the textural changes. Low-molecular weight polyols inhibited the collapse of gluten network and deterioration of noodle texture although they showed no inhibiting effect on microbial growth.
Assuntos
Qualidade dos Alimentos , Armazenamento de Alimentos/métodos , Glutens/química , Polímeros/química , Fenômenos QuímicosRESUMO
The quality properties of fresh noodles with NaCl and alkali were characterized by rheological, cooking, and texture properties. Microstructure, starch viscosity, protein conformation, gelatinization and protein polymerization during cooking, and water status were determined to investigate the mechanisms underlying their quality differences. The results showed that alkali induced more significantly increased (Pâ¯<â¯.05) gluten strength and noodle hardness, while NaCl resulted in superior dough extensibility. Pasting viscosity of alkali-flour increased and protein conformation changes were detected in alkaline noodles with increased ß-sheet and decreased α-helix structures. Both NaCl and alkali increased cooking loss. NaCl induced a fibrous gluten structure while alkali caused a membrane-like structure. Furthermore, remarkable protein aggregates were observed in alkaline noodles immediately after 2â¯min of cooking in non-reduced HPLC patterns, while 4â¯min in reduced patterns. Water-solids interaction in alkaline noodles was enhanced with decreased water mobility. NaCl induced no significant changes in protein aggregation and water status.
Assuntos
Culinária , Farinha , Qualidade dos Alimentos , Álcalis , Farinha/análise , Glutens/química , Proteínas de Plantas/química , Reologia , Cloreto de Sódio na Dieta , Amido/química , Viscosidade , Água , Grãos IntegraisRESUMO
The aim of this study was to develop an effective cell sheet translocation method using a cell adhesive and temperature-responsive hydroxybutyl chitosan hydrogel (HBC). The polydopamine (PD)-coated HBC hydrogels were prepared by the dopamine self-polymerization on the surface of HBC hydrogel with different coating time, termed as P30, P60 and P120, respectively. Gelling property of HBC was not affected by PD coating. The PD-coated HBC hydrogels promoted the attachment and proliferation of mouse fibroblast cells (L929) and human umbilical vein endothelial cells (HUVECs), and allowed formation of monolayer cell sheet. In vitro translocation of HUVECs sheet could be obtained successively through phase transition of PD coated HBC hydrogel from gel to sol, and the cells sheet transferred from P30 hydrogel to a round cell coverglass maintained relatively complete monolayer and normal cell morphology. The results showed that P30 hydrogel has the potential to be used for cell transplantation therapy.
Assuntos
Células Imobilizadas , Quitosana/análogos & derivados , Células Endoteliais da Veia Umbilical Humana , Hidrogéis/química , Indóis/química , Polímeros/química , Animais , Células Imobilizadas/metabolismo , Células Imobilizadas/transplante , Quitosana/química , Células Endoteliais da Veia Umbilical Humana/metabolismo , Células Endoteliais da Veia Umbilical Humana/transplante , Humanos , CamundongosRESUMO
Based on the critical water content (for noodle deterioration) concluded previously, high-temperature-short-time (HTST; 105-135°C) and medium-temperature-long-time (MTLT; 45-75°C) dehydrations were introduced in this study to produce semi-dried noodles. The effects of HTST and MTLT on the quality parameters of semi-dried noodles, as well as noodle structure, storage stability, and changes in starch and protein components were thoroughly investigated. Differential scanning calorimeter (DSC) and birefringent analysis presented few starch gelatinization (approximately 30%) in HTST dehydrated noodles. Scanning electron microscopy (SEM) images showed more compact noodle surface, with uniform pores in the cross section, probably due to enhanced protein-starch combination after HTST dehydration. Meanwhile, HTST induced protein polymerizations in semi-dried noodles, mainly by -SH-S-S interchange, and resulted in significantly (P<0.05) reduced cooking loss. Furthermore, HTST noodles showed higher microbial and color stability. Shelf-life of dehydrated samples at 120°C was extended to 5days from 1day of the control.