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1.
Food Chem ; 329: 126800, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32504915

RESUMO

The role of polyphenol oxidase (PPO) in the browning of fresh wet noodle sheets (FWNS) was discussed. To release the chemical formation mechanism of the dark spots formed on FWNS, the reconstituted FWNS and PPO-catechol reaction systems were prepared. Different from the overall color change of FWNS, almost all the melanins in dark spots were indirect products of PPO catalysis. The PPO catalytic dehydrogenation was an essential step for the formation of dark spots, but once the phenol dehydrogenation products were formed, the dark spots could still form through a further polymerization process, even though the PPO was completely deactivated. The optimum pH for the phenolic dehydrogenation in FWNS was about 7, and the alkaline condition was advantageous to the progress of the polymerization. Comprehensively, the maximum amount of dark spots was formed at about pH 9.

2.
Food Chem ; 330: 127319, 2020 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-32569936

RESUMO

The influence of fresh egg white (EW) addition on the quality characteristics and protein aggregation in oat noodles containing wheat flour and gluten was studied. EW addition decreased cooking loss and increased cooking time of 70% oat noodles. The hardness, chewiness, tensile force and tensile distance improved significantly. A smooth surface and continuous protein network were observed by scanning electron microscopy (SEM) after adding EW. After cooking, the peak area in SE-HPLC profile of 70% oat noodles with EW decreased obviously. The extractabilities of protein in sodium dodecyl sulfate containing medium (SDSEP) of cooked wheat and oat noodles under non-reducing condition were lower than those of samples under reducing condition. The protein bands changes in SDS-PAGE profiles showed that EW could induce disulfide cross-linking of proteins in noodles. EW addition promoted proteins interaction and improved the cooking and texture properties of oat noodles.

3.
Food Funct ; 11(4): 3420-3431, 2020 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-32236175

RESUMO

In this paper, sorghum grains were pretreated by roasting (RT), microwave (MW), stir-frying (SF) and heat-moisture treatment (HMT). The effects of pretreated sorghum grains on in vitro starch digestibility of sorghum dried noodles made from sorghum and wheat flour were investigated. The results showed that HMT treated noodles contained the highest amount of resistant starch (RS) and the lowest amount of rapidly digestible starch (RDS). The hydrolysis kinetic parameters and estimated glycemic index (eGI) decreased in all of the treated samples. The treated starches had lower molecular weight and less proportion of short chains of amylopectin than those of the untreated sample. X-ray diffraction demonstrated that the relative crystallinity of starch in noodles was increased by HMT and RT treatments while it was decreased by MW and SF treatments compared to untreated noodles. Fourier transform infrared (FTIR) analysis revealed that the short-range ordered degree and intra-molecular hydrogen bond intensity were both enhanced by thermal treatments. A tighter and smoother microstructure with fewer pores and cracks in the treated noodles was observed by scanning electron microscopy (SEM). These structural changes could provide a better understanding of the lower starch digestion rate.

4.
Food Chem ; 322: 126738, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32283361

RESUMO

Quality characteristics of whole wheat flour with superheated steam treatment and storage stability of semi-dried whole wheat noodle were investigated, as well as texture and cooking properties of cooking noodles. Superheated steam treatment significantly reduced the total plate count and the activities of lipase, lipoxygenase and polyphenol oxidase in whole wheat flour (p < 0.05), and decreased the free phenolic content. When treated at 155-170 °C, the thermomechanical properties of whole wheat dough improved with the increase of the development time, stability and C2 torque. Superheated steam treatment showed no obviously detrimental effects on hardness and cooking loss of noodle. During storage, treated semi-dried whole wheat noodle exhibited slower rate of microbial growth. Superheated steam treatment significantly reduced the acidity, inhibited the formation of free fatty acid, and decreased the activities of enzyme during storage. This would delay the deterioration and improve the storage stability of semi-dried whole wheat noodle.

5.
Food Chem ; 323: 126842, 2020 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-32334316

RESUMO

In this study, the effects of tempering with steam on the water distribution of wheat grains and the microbial load in wheat flour were investigated, as well as the physicochemical properties of wheat flour. Results showed that when steam treatment time was 320 s, the total plate count (TPC), yeast and mold count (YMC), and mesophilic aerobic spores (MAS) in flour decreased by 1.74, 1.99 and 1.01 lgCFU/g, respectively. Nuclear magnetic resonance (NMR) results showed that tempering with steam accelerated the water distribution of grains and significantly (p < 0.05) shortened the tempering time. Moreover, flour yield, particle size, ash content, and damaged starch content of flour were all altered. Furthermore, after tempering with steam, proteins were aggregated and starches were partially gelatinized, which caused dough development time and stability of flour increasing. Collectively, our findings indicated steam tempering could shorten the tempering time and improve the qualities of flour partly.

6.
Food Chem ; 320: 126606, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32203831

RESUMO

Chinese traditional hand-stretched dried noodle is very popular in China for its unique taste and flavor quality, and NaCl plays a vital role in its processing. The effects of NaCl (1%-6%, w/w) on rheological and gluten properties of dough of Chinese traditional hand-stretched dried noodle were studied. The addition of NaCl (1%-4% w/w) enhanced storage modulus, loss modulus and extensibility of dough, while these rheological parameters started to decreased when NaCl amount reached 5% (w/w). With salt addition increased from 0% to 6% (w/w), the solubility of gluten in SDS medium showed a significant (p < 0.05) decreasing trend, while opposite result was found on the yield and G' of gluten macro polymer. These changes on gluten indicated that the interaction among gluten molecules increased with the increase of salt amount. Excessive salt (5%-6%, w/w) disrupted the gluten network, which was responsible for the reduction of dynamic and extensional properties.

7.
Food Chem ; 283: 52-58, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30722907

RESUMO

The effects of alkali (NaHCO3 or Na2CO3) on the quality and protein polymerization of buckwheat Chinese steamed bread (CSB) were investigated. The alkali addition increased the specific volume of CSB, for NaHCO3 from 1.84 ml/g (control) to 2.66 ml/g. Image analysis showed that alkali increased the pore area fractions. The addition of Na2CO3 exhibited a greater pore count and lower pore average size. The texture properties were improved with the increase of crumb hardness and resilience. The extractability of protein in sodium dodecyl sulfate containing medium (SDSEP) decreased. Furthermore, SDS-PAGE showed an obvious decrease in the intensity of protein bands with lower molecular weight, while intensity of higher molecular protein bands increased. This demonstrated that alkali addition promoted protein aggregation in buckwheat CSB. In addition, the content of degydroalanine and lanthionine increased and free SH decreased, which indicated alkali addition prompted protein to form dehydroalanine-derived and disulfide cross-linkings.


Assuntos
Pão , Fagopyrum , Aminoácidos/análise , Pão/análise , Carbonatos/química , Dissulfetos/química , Eletroforese em Gel de Poliacrilamida , Qualidade dos Alimentos , Dureza , Peso Molecular , Polimerização , Bicarbonato de Sódio/química , Dodecilsulfato de Sódio/química , Vapor
8.
Food Chem ; 283: 522-529, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30722908

RESUMO

The effects of frozen storage on the quality of frozen cooked noodles were investigated. Texture analysis showed hardness and tensile force reduced during frozen storage. An increasing cooking loss and a decreasing water uptake ratio were determined when testing cooking qualities. As storage time prolonged, differential scanning calorimetry (DSC) detected more freezable water, and an increased relaxation time was recorded by nuclear magnetic resonance (NMR). Magnetic resonance imaging (MRI) revealed water distribution was more heterogeneous. A ruptured microstructure with large pores of frozen cooked noodles was observed by scanning electron microscopy (SEM). The confocal laser scanning microscope (CLSM) photographs demonstrated gluten network lost its integrity and compactness. Size-exclusion high performance liquid chromatography (SE-HPLC) indicated the amount of SDS-soluble proteins increased. The present study showed water characteristics and protein network underwent some changes during frozen storage, which had major effects on the quality of frozen cooked noodles.


Assuntos
Culinária , Armazenamento de Alimentos/métodos , Varredura Diferencial de Calorimetria , Cromatografia Líquida de Alta Pressão/métodos , Proteínas na Dieta/química , Análise de Alimentos/métodos , Congelamento , Glutens/química , Imagem por Ressonância Magnética , Microscopia Confocal , Água/química
10.
Food Chem ; 278: 333-341, 2019 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-30583380

RESUMO

Different methods used to process green tea powder noodles (GTPN) were compared by analyzing the quality and chemical components of the final products. Significant differences were observed in the discoloration rate, color loss, and lightness of all noodles. Polyphenol oxidase activity was effectively inhibited through the heat treatment, resulting in retardation of the GTPN discoloration rate. However, heat-exposed GTPN showed a higher surface lightness due to a greater loss of chlorophyll. The chlorophyll contents of GTPN prepared with a new method (a combination of water treatment and heat exposure) were prominently higher than those prepared by heat treatment alone, and exhibited less color loss. The heat-exposed noodles had relatively low free polyphenol contents, and their textural properties were not significantly decreased after 28 d. Therefore, combining water treatment and heat exposure in the preparation process has great potential for increasing the stability of GTPN.


Assuntos
Conservação de Alimentos/métodos , Armazenamento de Alimentos/métodos , Alimentos , Chá , Catecol Oxidase/química , Clorofila/análise , Clorofila/química , Cor , Farinha , Temperatura Alta
11.
Int J Biol Macromol ; 107(Pt A): 129-136, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-28863898

RESUMO

This paper studied the inhibition of water extract of natural or baked black tea on the activity of α-amylase and α- glucosidase. Baking treatment was found to be one effective way to enhance the inhibition of black tea on both α-amylase and α- glucosidase, and IC50 of water extract of baked black tea (BBTWE) were 1.213mg/mL and 4.190mg/mL, respectively, while IC50 of water extract of black tea (BTWE) were 1.723mg/mL and 6.056mg/mL, respectively. This study further studied the mechanism of the effect of water extract on α-amylase and α- glucosidase using HPLC, circular dichroism, and synchronous fluorescence. HPLC analysis of tea polyphenols showed that the content of tea polyphenols with low polarity increased after baking. In addition, BBTWE had higer abilty on decreasing the hydrophobicity of tryptophan residues than BTWE for both α-amylase and α- glucosidase.The increase of α-helix proportion of α-amylase when treated with BBTWE was more obvious than that when treated with BTWE. In a word, thermal process of baked foods may be beneficial for tea polyphenols to reduce the rate of starch digestion.


Assuntos
Extratos Vegetais/farmacologia , Chá/química , alfa-Amilases/antagonistas & inibidores , alfa-Glucosidases/química , Camellia sinensis/química , Inibidores de Glicosídeo Hidrolases/química , Inibidores de Glicosídeo Hidrolases/farmacologia , Interações Hidrofóbicas e Hidrofílicas , Extratos Vegetais/química , Polifenóis/química , Polifenóis/farmacologia , Amido/química , alfa-Amilases/química
12.
Food Chem ; 239: 579-587, 2018 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-28873608

RESUMO

The impact of alkali addition on the degree of gluten polymerization and textural characteristics of textured wheat protein was investigated. Results showed that the extrusion process increased the average molecular weight of gluten as evidenced by SDS-PAGE and SDS extractable protein. The addition of alkali not only promoted the degree of gluten polymerization, but also induced dehydroalanine-derived cross-linking. Alkali addition decreased the content of cystine and increased the contents of dehydroalanine and lanthionine. The obvious decrease of free SH showed that dehydroalanine-derived cross-linking was quantitatively less crucial than disulfide cross-linking. Furthermore, the protein cross-linking induced by alkali improved the texture properties of gluten extrudates. SEM analysis showed extrusion under alkaline condition conferred a more fibrous microstructure as a consequence of a compact gluten network.


Assuntos
Triticum , Álcalis , Eletroforese em Gel de Poliacrilamida , Glutens , Proteínas de Plantas , Polimerização
13.
J Agric Food Chem ; 65(29): 6063-6069, 2017 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-28672109

RESUMO

Barley (Hordeum vulgare L.) ß-glucan (BBG) is of interest as a result of its health benefits, but BBG presents significant disruptions on the gluten network, with a negative impact on food texture. To clarify the interaction between BBG and gluten in dough, the dynamic rheological, thermochemical process of gluten and microstructure of dough with BBG during heating were detected. The results showed that BBG delayed the gluten thermopolymerization reaction during heating and affected polymerization of specific molecular weight protein subunits. These impacts depended upon the heating temperature and time. When heating under 25-65 °C, tan δ of the dough reached the highest level at the BBG concentration of 1%. However, under the temperature of 65-95 °C, tan δ was positively correlated with the BBG content (0-3%). The differential scanning calorimetry curves revealed that the peak temperature (TP) of the two endothermic peaks increased by 3.86 and 3.10 °C. Size-exclusion high-performance liquid chromatography analysis showed that BBG mainly affected the peak area of gliadin and glutenin. Furthermore, after 3% BBG was added, the bands of 59.8 and 64.9 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns delayed, vanishing for 120 s when heating at 95 °C. Therefore, BBG delayed the polymerization reaction of specific molecular weight protein subunits rather than all of the proteins.


Assuntos
Glutens/química , beta-Glucanas/química , Varredura Diferencial de Calorimetria , Culinária , Farinha/análise , Hordeum/química , Temperatura Alta , Polimerização , Reologia
14.
Food Chem ; 227: 264-270, 2017 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-28274431

RESUMO

Methoxy-ρ-benzoquinone (MBQ) and 2, 6-dimethoxy-ρ-benzoquinone (DMBQ) are two potential anticancer compounds in fermented wheat germ. In present study, modeling and optimization of added macronutrients, microelements, vitamins for producing MBQ and DMBQ was investigated using artificial neural network (ANN) combined with genetic algorithm (GA). A configuration of 16-11-1 ANN model with Levenberg-Marquardt training algorithm was applied for modeling the complicated nonlinear interactions among 16 nutrients in fermentation process. Under the guidance of optimized scheme, the total contents of MBQ and DMBQ was improved by 117% compared with that in the control group. Further, by evaluating the relative importance of each nutrient in terms of the two benzoquinones' yield, macronutrients and microelements were found to have a greater influence than most of vitamins. It was also observed that a number of interactions between nutrients affected the yield of MBQ and DMBQ remarkably.


Assuntos
Antineoplásicos/metabolismo , Benzoquinonas/metabolismo , Triticum/metabolismo , Algoritmos , Fermentação , Redes Neurais de Computação , Triticum/química , Triticum/genética
15.
Food Chem ; 221: 1178-1185, 2017 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-27979076

RESUMO

The impact of alkali addition on the dough rheological properties and quality of buckwheat noodles was investigated. Farinograph measurements showed that the addition of alkali increased the water absorption and development time of the dough. Dynamic rheological properties analysis showed that alkali addition enhanced G' and G″ of dough. In addition, the texture properties of buckwheat noodles improved by the increase of the hardness and tensile force. Furthermore, an obvious decrease in the intensity of the protein bands with lower molecular weights was observed in SDS-PAGE patterns and the extractability of protein in sodium dodecyl sulfate containing medium (SDSEP) decreased, which demonstrated that alkali addition promoted the degree of protein polymerization in the buckwheat noodles. CLSM analysis showed alkali addition produced a tight and continuous protein network in buckwheat noodles. The protein cross-linking induced by alkali improved rheological properties of dough and texture properties of buckwheat noodles.


Assuntos
Álcalis/química , Culinária , Reagentes para Ligações Cruzadas/química , Fagopyrum/química , Farinha/análise , Proteínas de Plantas/química , Eletroforese em Gel de Poliacrilamida , Farinha/normas , Qualidade dos Alimentos , Fenômenos Mecânicos , Polimerização , Reologia , Água/química
16.
Food Chem ; 216: 374-81, 2017 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-27596433

RESUMO

In this study, changes in fresh noodles during storage were evaluated at the physico-chemical, structural, and molecular levels. An increase in TPC and decrease in L(∗) value mostly occurred during the first 24h; the pH value significantly decreased (P<0.05) and proteins were partially depolymerized with the deterioration of fresh noodles, as evidenced by free amino acid determination and SDS-PAGE. Changes were also detected in the pasting and viscosity properties of the starch component. Moreover, the water sorption isotherm of fresh noodles decreased during storage, and the NMR transverse relaxation peak shifted right with an increased peak area between 10 and 100ms. MRI images showed that with increased storage time, the original structure was damaged and water distribution became non-uniform and migrated to the surface. TPC, pH, and L(∗) value were selected as the visualized parameters to characterize the fresh noodle deterioration, based on the correlation and factor analyses.


Assuntos
Análise de Alimentos , Proteínas/química , Amido/química , Eletroforese em Gel de Poliacrilamida , Armazenamento de Alimentos , Concentração de Íons de Hidrogênio , Imagem por Ressonância Magnética , Espectroscopia de Ressonância Magnética , Viscosidade , Água
17.
Food Chem ; 217: 28-36, 2017 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-27664604

RESUMO

To improve the nutritional, physical and flavor properties of wheat bran, yeast and lactic acid bacteria (LAB) were used for fermenting wheat bran in solid state. Appearance properties, nutritional properties, microstructure, hydration properties and flavor of raw bran and fermented bran were evaluated. After treatments, water extractable arabinoxylans were 3-4 times higher than in raw bran. Total dietary fiber and soluble dietary fiber increased after solid state fermentation. Over 20% of phytic acid was degraded. Microstructure changes and protein degradation were observed in fermented brans. Water holding capacity and water retention capacity of fermented brans were improved. Results suggest that solid state fermentation is an effective way to improve the properties of wheat brans.


Assuntos
Fibras na Dieta/análise , Fibras na Dieta/metabolismo , Fermentação , Aromatizantes/química , Xilanos/análise , Lactobacillaceae/química , Ácido Fítico/metabolismo , Leveduras/química
18.
J Sci Food Agric ; 97(10): 3181-3188, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27885676

RESUMO

BACKGROUND: Bitter taste is the main limiting factor for various applications of protein hydrolysates. Frequently used physicochemical methods for debittering protein hydrolysates come with some undesired side effects. Deamidation-induced modification would be a very promising technique to improve the flavor of wheat gluten hydrolysates (WGHs). This study was designed to determine the effect of deamidation with certain enzymes or acid treatment on the chemical composition, bitterness and umami properties of WGHs. The difference between umami peptide and free glutamic acid on the suppression of bitterness is emphatically discussed. The optimal scheme is proposed based on the flavor of WGHs and the yield of peptides. RESULTS: The generation of umami substances suppressed bitter signal transduction. When the content of umami substances was relatively high, the umami-enhancing properties of umami peptides were obviously effective. The intensity of umami taste was high enough to further suppress bitter taste in the course of neurocognitive functioning. CONCLUSION: When WGHs were treated with Glutaminase for 180 min, the umami taste score increased from 1.62 to 4.27 and the bitter taste score decreased from 1.33 to 0.65. © 2016 Society of Chemical Industry.


Assuntos
Aromatizantes/química , Glutens/química , Triticum/química , Nariz Eletrônico , Ácido Glutâmico/análise , Humanos , Hidrolisados de Proteína/química , Paladar
19.
Food Chem ; 201: 275-83, 2016 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-26868577

RESUMO

Polymerization of gluten and the changes of glutenin macropolymer (GMP) during the production of Chinese steamed bread (CSB) were investigated, providing a theoretical basis to improve and regulate the quality of CSB. Protein extractability and free sulfhydryl (SH) contents increased to some degree during the dough preparation stage, but significantly (P<0.05) decreased during steaming. Remarkable protein aggregates were observed in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns. The microstructure study of the gas cell and the protein network by confocal laser scanning microscopy (CLSM) further revealed the formation of a continuous and three-dimensional gluten network. The loss and recovery of GMP wet weight during dough processing were significant (P<0.05). Glutenin depolymerization negatively correlated with GMP wet weight and the contents of high molecular weight glutenin subunits (HMW-GS) and low molecular weight glutenin subunits (LMW-GS). Gluten polymerization led to a decrease in G' and G″ of GMP while gluten depolymerization induced a slight recovery in G' and G″ of GMP.


Assuntos
Pão/análise , Glutens/química , Triticum/química , Eletroforese em Gel de Poliacrilamida/métodos , Polimerização , Vapor
20.
Food Chem ; 194: 797-804, 2016 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-26471620

RESUMO

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.


Assuntos
Farinha/análise , Manipulação de Alimentos/métodos , Armazenamento de Alimentos/métodos , Amido/química
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