Multilevel Structure of Wheat Starch and Its Relationship to Noodle Eating Qualities

The Influence of Rice Protein, Hemp Protein and Transglutaminase Addition on the Quality of Instant Fried Noodles

The goal of this study was to determine the effect of rice and hemp protein addition together with transglutaminase on the quality and fat content of fried instant noodles. The following parameters have been analyzed during this research: the amount of water, fat content, hydration time, color and texture parameters. The evaluation of sensory parameters before and after cooking of instant noodles has been performed. It can be concluded that the addition of TGase significantly decreased the fat content; the recipe with a 3% hemp protein addition with TGase in an amount of 2% was the most promising solution to obtain a low-fat product. On the other hand, the better consumer acceptance levels were observed for the rice protein addition (1%) with 2% TGase. It seems that the most promising product is the sample with a 5% addition of rice protein with 2% TGase-a reduction in the fat content by 30% (from 25% to 16%). The addition of rice protein, hemp protein and TGase reduced the fat content of the instant noodles in comparison to the control sample. The additives used had an impact on the L*, a* and b* color parameters. All instant noodles obtained during the research process were characterized by a short hydration time, which did not exceed 5 min. During the sensory evaluation, analyzed samples of the instant noodles obtained scores higher than 4.2 points on a five-point scale.

New insights into how starch structure synergistically affects the starch digestibility, texture, and flavor quality of rice noodles

The functionalities of gluten-free rice noodles are significantly affected by starch hierarchical structures. Identifying the structures that synergistically determine noodle integrated functionalities is vital to designing health-promoting starchy foods with desirable consumer sensory and nutritional qualities. This study reports on the changes in starch structures and functionalities (starch digestibility, texture, and flavor) of rice noodles during household cooking processes (steaming, boiling, and stir-frying), and describes an underlying structure-functionality relationship. Results show that all the cooking processes examined increased starch reassembled ordered structures, especially short-range ordered structures, helical and crystalline structures, and ordered aggregate structures. Steaming and boiling led to a decrease in rapidly digestible starch (RDS) and an increase in slowly digestible starch, while stir-frying yielded a reduction in RDS content and an increase in resistant starch in rice noodles. Steaming and boiling decreased while stir-frying increased the flavor variety of noodles. All cooking processes examined altered noodle textures, with a significant increase in hardness, gumminess, and chewiness. Structure-functionality relationships suggested short-range ordered structures, crystalline structures, and the ordered molecular and aggregate structures of noodles synergistically determined starch digestion, texture, and flavor. By structuring such key structures, the digestion, texture, and flavor of rice noodles can thus be reasonably controlled.

Ordered structural changes of retrograded starch gel over long-term storage in wet starch noodles

Temperature-induced structural variations of retrograded starch gel during long-term storage were investigated in a real food system (wet starch noodles). Fresh starch noodles presented a B-type XRD pattern containing 8.82% crystallinity and 16.04% double helices. In the first 2 weeks, double helices of starch chain formed long-range ordered structure leading to increased crystallinity, and such structural transformation was positively correlated with increasing storage temperature (from 4 °C to 35 °C) and storage time. However, with the extension of storage time to 12 weeks, the disorganization of supra-molecular structure was likely to be observed by decreased crystallinity, double helix and water mobility. Besides, we propose that the area and intensity of Raman band at 2910 cm^-1 can be a good indicator for evaluating perfection of crystallinity in starch noodles. These results contributed to a better understanding of mechanisms underlying molecular order changes of retrograded starch gel product during long-term storage.

Rheological behaviors and physicochemical changes of doughs reconstituted from potato starch with different sizes and gluten

The effects of different sizes of potato starch on the rheological and physiochemical properties of model doughs were investigated. Compared with those of model dough prepared from original starch, the strengths of model doughs prepared from fractionated starch were higher, which indicates that fractionated starch can positively influence the properties of doughs. Additionally, the model dough prepared using large size starch granules had higher storage modulus (G'), loss modulus (G''), and composite modulus (|G*|) values compared to those of other types of dough; it also had the highest elasticity, viscosity, and strength. This might be related to its high amylose content (20.28 ± 0.69%) and high 1045 cm^-1/1022 cm^-1 ratio (1.27 ± 0.17). The model dough (S) prepared from starch with small sizes had the highest contents of disulfide bonds (2.91 μmolg^-1), β-turn (33.92 ± 1.17%), and β-sheet (22.57 ± 0.54%); and it also had better network structure and dough stability. Thus, the stability of the S model dough was affected by phosphorus (1194.57 ± 25.32 ppm) and amylopectin (84.19 ± 1.88%) content, and, moreover, by the competition for water. Stability and network structure of dough are relative to the size distribution of starch granules. Finally, a schematic model showing the mechanism of the influence of phosphorus, sulfhydryl, and disulfide bonds in fractionated starch on the rheological properties of dough was developed.

Structural breakdown of starch-based foods during gastric digestion and its link to glycemic response: In vivo and in vitro considerations

The digestion of starch-based foods in the small intestine as well as factors affecting their digestibility have been previously investigated and reviewed in detail. Starch digestibility has been studied both in vivo and in vitro, with increasing interest in the use of in vitro models. Although previous in vivo studies have indicated the effect of mastication and gastric digestion on the digestibility of solid starch-based foods, the physical breakdown of starch-based foods prior to small intestinal digestion is often less considered. Moreover, gastric digestion has received little attention in the attempt to understand the digestion of solid starch-based foods in the digestive tract. In this review, the physical breakdown of starch-based foods in the mouth and stomach, the quantification of these breakdown processes, and their links to physiological outcomes, such as gastric emptying and glycemic response, are discussed. In addition, the physical breakdown aspects related to gastric digestion that need to be considered when developing in vitro-in vivo correlation in starch digestion studies are discussed. The discussion demonstrates that physical breakdown prior to small intestinal digestion, especially during gastric digestion, should not be neglected in understanding the digestion of solid starch-based foods.

Effect of cassava starch structure on scalding of dough and baking expansion ability

Fermented cassava products are important starchy food staples in South America. The quality of the products is affected by the baking expansion ability of the dough, which is in turn influenced by the starch fermentation process and drying method employed. We investigated the structural properties of cassava starch after different fermentation and drying treatments, and the effect of starch structure on scalding of dough and baking expansion ability. Fermentation combined with either exposure to sunlight or UV light treatment resulted in high cassava starch baking expansion. Moreover, we observed decreased crystallinity and increased disordered crystalline regions with lower molecular weight in the two types of starch-fermented combined with sunlight or UV light treatment-and both appeared to have a continuous network structure and polarized cross in scalded dough, which are conducive to holding gas and losing water, thus promoting high baking expansibility.

The addition of alpha amylase improves the quality of Chinese dried noodles

The effect of α-amylase on the quality attributes of Chinese dried noodles (CDN) was investigated. Adding α-amylase markedly decreased the cooking time and cooking loss of CDN at the level of 12.5 (mg/100 g flour). The elasticity of CDN was increased significantly (P < 0.05) after adding α-amylase. The firmness of noodles with 12.5 mg α-amylase per 100 g flour showed no obvious change compared to the control, whereas it decreased significantly (P < 0.05) when the amount of α-amylase increased to 25 (mg/100 g flour). In addition, the chewiness of CDN with 12.5 mg α-amylase per 100 g flour increased, while it showed a significant (P < 0.05) decreasing trend with further increased α-amylase levels. Starch structural and thermal properties were also changed by α-amylase, which showed increased relative crystallinity, swelling power, but decreased pasting property. The changed starch property restrained the cross-linking of gluten. The decrease in optimal cooking time and increase in elasticity of CDN were due to the increased swelling power and decreased peak time of the starch. In addition, the decreased setback of starch and protein cross-linking degree were responsible for the decreased firmness and chewiness of CDN with α-amylase ranging from 25 to 50 mg/100 g flour. Overall, α-amylase could be used as a functional additive to improve the quality of CDN when the amount was at 12.5 mg/100 g flour.

Quality Differences between Fresh and Dried Buckwheat Noodles Associated with Water Status and Inner Structure

Buckwheat noodles are mainly sold in the form of fresh and dried noodles in China. Among the noodles with varied proportions of extruded buckwheat flour (20% to 80%), the cooking or textural qualities of fresh and dried buckwheat noodles (FBN and DBN, respectively) were significantly different, and FBN showed a lower cooking loss and breakage ratio and were more elastic than DBN. FBN-20% showed the highest sensory score, followed by DBN-50%. The mechanisms causing the quality differences were investigated using water mobility and the internal structures of the noodles were investigated with low-field nuclear magnetic resonance and scanning electron microscopy, respectively. Compared with FBN, DBN showed a denser internal structure, which explained its higher hardness. The water within FBN and DBN was mainly in the form of softly bound water and tightly bound water, respectively. FBN with highly mobile softly bound water (longer T 22) and a more uniform internal structure had a lower breakage ratio, whereas the trends of water relation with texture properties were different for FBN and DBN. The drying process and added extruded buckwheat flour together contributed to the varied cooking and textural properties.

Structural basis of wheat starch determines the adhesiveness of cooked noodles by affecting the fine structure of leached starch

The relationship between the fine structure of original starch, leached starch during cooking, and the adhesiveness of noodles prepared by adding starches separated from different wheat cultivars was analyzed. The adhesiveness of noodles was primarily determined by the chain-length distributions of amylopectin rather than amylose. The adhesiveness of cooked noodles was positively correlated with the amount of short amylopectin chains with the degree of polymerization (DP) of 6-12, but negatively correlated with the amount of long chains with 25 < DP ≤ 36. The decrease of the proportion of short amylopectin chains and amylose chains and the increase of the amount of very long amylopectin chains with 37 < DP ≤ 100 in leachate led to decreased adhesiveness of cooked noodles. The reduction of the short-chain content in leached amylopectin caused by the increased proportion of long chains in original amylopectin is proposed to weaken the adhesiveness of cooked noodles.

Sandwich-type sheeting improved the processing and eating qualities of potato noodles

A technology called sandwich-type sheeting was used to produce noodles with potato flakes. The technical parameters of sheeting were first optimized. Then the processing and eating qualities of potato noodles made with sandwich-type sheeting and conventional sheeting were compared. Results showed that the optimal moisture of inner-layer dough and outer-layer dough was 41 and 37%, respectively. The suitable ratio of the thickness of inner layer to that of outer layer was 3:1. The tensile strength of the sandwich-type dough sheet was 1.285 times higher than that of conventional dough sheet. The cooking loss of the sandwich-type noodles was 37.0% lower than that of conventional noodles, and the adhesiveness decreased by 51.0%. In the sandwich-type noodles, the compact gluten network structure of outer wheat layer prevented the leaching of soluble substances in the inner layer added with potato flakes, improving the cooking and eating qualities of potato noodles.

Effects of the size distribution of wheat starch on noodles with and without gluten

To understand the effects of A- and B-type wheat starch on noodle quality, two noodle models with (Model 1) and without (Model 2) gluten were constructed with five different ratios of A- to B-granules (100A-0B, 75A-25B, 50A-50B, 25A-75B, and 0A-100B). With increasing proportions of B-granules, the noodle structures of Models 1 and 2 became increasingly dense. The cooking loss, water absorption, proportion of free water, chewiness, cohesiveness and resilience decreased from 35.64 to 15.49%, 240.92 to 228.58%, 88.89 to 85.98%, 21.93 to 13.24 N, 0.77 to 0.56, and 0.61 to 0.36, respectively, with the increased proportion of B-granules in Model 2, while those parameters normally presented "V" or inverted "V" trends in Model 1. Compared to their counterparts in Model 2, gluten networks with 25-50% B-granules had an outstanding ability to increase the percentage of tightly bound water, hardness, chewiness and springiness by 4.50%, 24.07 N, 25.05 N, and 0.17 at most and reduce the proportion of free water and water absorption by 5.56 and 73.70% at most, respectively. The results indicated that the effect of the gluten network on noodle qualities may partially depend on its structure, which is shaped by the granule size distribution. Compared to the other characteristics of noodles, the springiness was influenced by a more complicated mechanism involving A- and B-granules in Model 2, while it was strongly affected by the gluten network under the given experimental conditions in Model 1.

The contribution of β-glucan and starch fine structure to texture of oat-fortified wheat noodles

Wheat flour noodles are sometimes fortified with β-glucan for nutritional value, but this can decrease eating quality. The contributions of β-glucan and starch molecular fine structure to physicochemical properties of wholemeal oat flour and to the texture of oat-fortified white salted noodles were investigated here. Hardness of oat-fortified noodles was controlled by the longer amylopectin chains (DP ≥ 26) and amount of longer amylose chains (DP ≥ 1000). Higher levels of β-glucan, in the range from 3.1 to 5.2%, result in increased noodle hardness. Pasting viscosities of wholemeal oat flour positively correlate with the hardness of oat-fortified noodles. The swelling power of oat flour is not correlated with either pasting viscosities of oat flour or noodle hardness. Longer amylopectin chains and the amount of longer amylose chains both control the pasting viscosities of oat flour, which in turn affect noodle texture. This provides new means, based on starch and β-glucan molecular structure, to choose oats with optimal starch structure and β-glucan content for targeted oat-fortified noodle quality.

A combined action of amylose and amylopectin fine molecular structures in determining the starch pasting and retrogradation property

Starch fine molecular structures are of essentially important in determining its pasting and retrogradation properties. In this study, 10 different starches from various botanical sources were selected to investigate the combined action of amylose and amylopectin molecules in determining the starch physicochemical properties. Correlation between starch structural parameters with the pasting and retrogradation properties showed that amylose and amylopectin CLDs do not affect these properties in isolation. Such as, the amount of amylose long chains and amylopectin short chains are both positively correlated with the melting temperatures and enthalpy of retrograded starches. Furthermore, relatively longer amylose short to medium chains can result in higher trough and breakdown viscosity, while higher amount of amylopectin medium to long chains result in higher peak viscosity. The results help a better understanding of the importance of amylose and amylopectin fine molecular structures in determining starch functional properties.

Protein-starch matrix plays a key role in enzymic digestion of high-amylose wheat noodle

Wheat flour, consisting of a complex matrix of starch and protein, is used as a representative model of whole food here to investigate the binary interaction in relation to amylose level and hydrothermal treatment in noodles as a food exemplar. Noodle made of high-amylose wheat (HAW) flour showed an eight-fold higher resistant starch content, compared to the wild type. Protein removal under simulated intestinal digestion conditions resulted in higher starch digestion rate coefficients in raw and cooked flours. In cooked flours, the substrate becomes similarly accessible to digestive enzymes regardless of protein removal. The results indicate that the increased protein content in native HAW flour and thermal stability of starch in HAW noodles lead to higher food integrity and consequently enhance the resistance against α-amylase digestion. Overall, the study suggests that a diversity of starch-protein interactions in wheat-based food products underlies the nutritional value of natural whole foods.

The effect of retrogradation time and ambient relative humidity on the quality of extruded oat noodles

Commercial process of oat noodles was mainly hindered by its lack of gluten and difficulty in forming dough. Extrusion could be an effective method to produce oat noodles by forming network of gelatinized starch, and noodle quality could be improved by regulating the retrogradation process. In this study, we produced oat noodles by two-step extruding and investigated the effect of retrogradation treatment (retrogradation time and ambient relative humidity) on noodle properties. At each corresponding ambient relative humidity (RH), the starch crystallinity and enthalpy value increased, while setback value decreased, as well as noodle cooking loss was significantly improved as retrogradation time increased to 48 hr, and then decreased at 72 hr. At the same retrogradation time, the starch crystallinity, setback, and enthalpy value decreased to RH70% and then had a slight rise at RH80%, while noodle cooking loss with reversal trend. The retrogradation time of 48 hr and ambient RH of 60% could be an optimum treatment for effectively improving extruded oat noodle quality. Furthermore, multivariate data analysis indicated that samples at the same ambient RH tended to be clustered together. This study could provide basic knowledge for controlling processing condition of the extruded oat noodle.

Parameterizing starch chain-length distributions for structure-property relations

Understanding starch structure-property relationship is important for the development of new generation of starch-based foods with desirable functions. Recent developments of methodologies on the characterisation of starch molecular structures, especially how to parameterize the starch chain-length distribution (CLD) by few biologically meaningful parameters have brought new insights to explain starch physicochemical properties from molecular levels. Especially, it has shown that gelatinization temperatures are largely controlled by amylopectin short chains, while the retrogradation rate of starch molecules is controlled by amylose content, amylose short to medium chains, amylopectin external and internal chain length. Starch pasting and digestion properties are also controlled to a significant extent by its CLD. With extensive discussion of correlative and casual relations between starch CLD with its physicochemical properties, this review aims to establish a holistic starch structure-property relationship. It enables food producers to develop functional foods based on a precise understanding of starch structure-property relations.

RS Content and eGI Value of Cooked Noodles (I): Effect of Cooking Methods

Noodles are widely consumed in China, which can be cooked in different ways. The effects of different cooking methods (boiling, steaming, microwave heating, stir-frying and frying) on the resistance starch (RS) content and digestive properties (digestion rate, digestibility and estimated glycemic index (eGI) value) of noodles were investigated. The RS content was greatly affected by the cooking time, and it was varied when the noodles were optimally cooked using different cooking methods. The RS contents of the microwaved and stir-fried noodles were relatively high (0.59%-0.99%), but it was lower (0.43%-0.44%) in the boiled and steamed noodles. Microwaved noodles showed the slowest digestion rate and the lowest eGI. Due to the limited water within fried noodles, none RS was found in the fried noodles, whereas stir-fried noodles showed RS5 formation from the XRD and DSC results. Compared with boiled and steamed noodles, the microwaved noodles showed a more compact morphology without porous holes on the surface, whereas fried noodles showed irregular morphology. The results indicated that the digestive properties of noodles made with the same ingredients can be greatly altered by using different cooking methods, and the digestive properties of different cooked noodles are worthy of confirmation using in vivo analysis.

Deterioration mechanisms of high-moisture wheat-based food - A review from physicochemical, structural, and molecular perspectives

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.

Reduction of microbial load in yellow alkaline noodle using optimized microwave and pulsed-UV treatment to improve storage stability

Pulsed-UV is an emerging innovation in non-thermal processing and is scarcely explored. This study introduces a combined treatment of microwave and pulsed-UV to reduce the microbial load in yellow alkaline noodle (YAN), a popular staple food among South East Asians that is easily perishable, without jeopardising its textural qualities. Results indicated that the combination of 5 s microwave (power = 900 W; frequency = 2450 MHz) and 3.5 J/cm2 pulsed-UV significantly reduced aerobic plate count and spore forming bacteria, from 637.5 to 50 CFU/g and 1500 to 100 CFU/g, respectively. In terms of textural properties, even though significant changes were detected in hardness and springiness for treated YAN kept at ambient storage as compared to control, the alterations were not prominent. Based on these observations, it is concluded that a combined treatment of microwave and pulsed-UV successfully improved the shelf life of YAN at ambient storage by 50%, from 1.0 day (control) to 1.5 days (treated sample) and by 140%, from 2.0 to 4.8 weeks at chilled storage. Current study proves the potential of microwave + pulsed-UV, a "green" hurdle treatment, to extend the shelf life of preservative-free YAN without causing major undesirable textural alterations on the noodle.