Humidity-controlled heat treatment of fresh spinach noodles for color preservation and storage quality improvement.

The high sensitivity to color browning during room-temperature storage was a significant factor in limiting the development of fresh spinach noodles (FSN). The practice of humidity-controlled heat treatment (HCHT) at varying temperatures, relative humidity, and time was carried out to limit enzyme activity and improve the quality of FSN. Results showed that HCHT could maximize the color preservation of fresh spinach noodle quality while effectively inactivating polyphenol oxidase and the yeasts, and mold count in FSN during storage was almost undetectable after mild conditions (80 °C). The hardness and chewiness of HCHT noodles were significantly increased, but the free sulfhydryl content was reduced. At 80 °C, 90 %, 5 min, protein structural aggregation was found in the microstructure of HCHT fresh spinach noodles. HCHT also caused partial gelatinization, as evidenced by the decrease in starch gelatinization enthalpy from 5.49 to 4.77 J/g, although the gelatinization degree of FSN was comparatively low.

Inhibitory mechanism of sodium hexametaphosphate on enzymatic browning in yellow alkaline noodles.

The effect and mechanism of sodium hexametaphosphate (SHMP) on polyphenol oxidase (PPO) enzymatic browning in yellow alkaline noodles (YAN) were investigated. The browning degree and PPO activity in YAN or PPO solutions decreased with the SHMP concentrations increased. Variations in pH values (pH 7-8.5) adjusted by HCl or acetic acid slightly affected the PPO activity, but SHMP inhibited PPO activity more pronounced. The inhibition of SHMP on PPO activity was irreversible. SHMP formed coordinate covalent bonds with Cu2+ to make PPO inactive. HPLC analysis revealed that SHMP reduced the browning products and led to the color of PPO-catechol systems being lightened. Furthermore, SHMP inhibited browning by hampering the auto-oxidization of intermediate products due to the change in pH value. Besides, the HPLC chromatogram, UV-vis spectrum, and mass spectrometry revealed that SHMP could convert melanin (m/z 248.97, 723.5, and 836.58) to light-colored substances (m/z 137.11).

Inhibition of L-Cysteine on the Browning of Fresh Wet Noodles.

This research explored the effect of L-cysteine on the browning of fresh wet noodles (FWN). With the increasing addition of L-cysteine (0.02-0.1%), the ΔL* decreased and Δa*, Δb* increased. The L-cysteine could reduce the pH value and polyphenol oxidase (PPO) activity and increase the retention rate of polyphenol of FWN. It suggested that L-cysteine could inhibit the browning of FWN by decreasing pH value, PPO activity, and the oxidation of polyphenols. In the in vitro PPO solution, the inhibitory effect of L-cysteine on PPO activity was related to the decrease in pH and the ability of chelating Cu2+. According to UPLC-TOF-MS analysis, L-cysteine could reduce the generation of browning products, which suggested that L-cysteine could react with the browning intermediate product (quinone) and generate a light-colored substance (-C9H10NO4S). L-cysteine effectively inhibited the browning of FWN and had the potential to be used in noodle industry.

Influence of ε-poly-l-lysine treated yeast on gluten polymerization and freeze-thaw tolerance of frozen dough.

The effects of ε-poly-l-lysine (ε-PL) treated yeast on gluten polymerization of frozen dough and quality of steamed bread after freeze-thaw cycles were investigated. Compared with steamed bread made from frozen dough containing ε-PL and untreated yeast (PUTY) or only untreated yeast, steamed bread made from frozen dough containing ε-PL treated yeast (PTY) had a larger specific volume, lower hardness and more porous. A dynamic rheological and scanning electron microscopic analysis demonstrated that using PTY instead of yeast could reduce dough elasticity and damage protein network after freeze-thaw cycles. Lower sodium dodecyl sulfate (SDS) soluble polymeric proteins and monomeric proteins, and higher SDS insoluble proteins were found in frozen dough containing PTY, which indicates a reduced depolymerization of gluten proteins after freeze-thaw cycles. After 4 freeze-thaw cycles, the lower glutathione and free sulfhydryl in dough containing PTY indicate that the interchain disulfide bonds between proteins were preserved.

Inhibition of hexose oxidase on the dark spots in fresh wet noodle sheets: A feasible prevention of dark spots.

Hexose oxidase was a feasible prevention for the dark spots in the fresh wet noodle sheets (FWNS). The chemical mechanism that hexose oxidase recucing the melanins of dark spots was discussed basis on the UPLC-TOF-MS analysis of the polyphenol oxidase (PPO)-catechol system. In the process of PPO browning, hexose oxidase catalyzed the oxidation of o-benzoquinone derivatives and their oligomers, hindering the formation of melanins. Hexose oxidase was efficient in FWNS with low ash content when water addition was 24%~44% or pH range was 4 ~ 7.5. Hexose oxidase could inhubit dark spots in the presence of 10 metal ions. The recommended addition amount was 40 ~ 60 ppm, by which the dark spots could be compolitely inhibited. Hexose oxidase was also suitable for wholewheat and oat FWNS, ΔL6d of wholewheat and oat FWNS were reduced by 4 and 7.98, respectively.

Polyphenol oxidase browning in the formation of dark spots on fresh wet noodle sheets: How dark spots formed.

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.

Effect of superheated steam treatment on quality characteristics of whole wheat flour and storage stability of semi-dried whole wheat noodle.

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.

Increasing the physicochemical stability of stored green tea noodles: Analysis of the quality and chemical components.

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.

The enhanced inhibition of water extract of black tea under baking treatment on α-amylase and α-glucosidase.

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.

Effects of alkali on protein polymerization and textural characteristics of textured wheat protein.

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.

Artificial neural network - Genetic algorithm to optimize wheat germ fermentation condition: Application to the production of two anti-tumor benzoquinones.

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.

Functional properties of chitosan-xylose Maillard reaction products and their application to semi-dried noodle.

The objective of this research was to evaluate the antimicrobial, antioxidant and darkening inhibitory activities of Maillard reaction products (MRPs) prepared from chitosan and xylose, and their effects on the preservation and quality of semi-dried noodles. The development of brown color and UV absorbance changes indicated the proceeding of Maillard reaction. The antimicrobial activity, reducing power, DPPH radical scavenging activity, copper-chelating activity and PPO inhibitory effects of chitosan-xylose conjugates increased with the reaction. Addition of MRPs could improve the textural and cooking quality of semi-dried noodles. Incorporation of 0.35% MRPs (6 h) into semi-dried noodle resulted in an extension of shelf life for more than 7 days than the control noodles (at room temperature). The discoloration caused by the addition of MRPs was limited, and MRPs could inhibit darkening of the noodle effectively. Results suggested that the MRPs could be used as a novel promising preservative for semi-dried noodles.

Evaluation the quality characteristics of wheat flour and shelf-life of fresh noodles as affected by ozone treatment.

In this study, the effects of ozone treatment on the microorganism mortality in wheat flour and shelf-life of fresh noodles were investigated, as well as the physicochemical properties of wheat flour and textural qualities of cooked noodles. Results showed that the total plate count (TPC) can be largely reduced in wheat flour exposed to ozone gas for 30 min and 60 min. Whiteness of flour and noodle sheet, dough stability, and peak viscosity of wheat starch were all increased by ozone treatment. Free cysteine content in wheat flour was shown to decrease significantly (P<0.05) as the treatment time increased and remarkable protein aggregates were observed in both reduced and non-reduced SDS-PAGE patterns. In addition, ozone treated noodles were generally higher in firmness, springiness, and chewiness, while lower in adhesiveness. Microbial growth and darkening rate of fresh noodles made from ozone treated flour were delayed significantly.