D-Glucose Assay Kit (GOPOD Format)

A simple method for measurement of the amylolytic activity of malt has been developed and fully evaluated. The method, termed the Maltose Value (MV) is an extension of previously reported work. Here, the MV method has been studied in detail and all aspects of the assay (sample grinding and extraction, starch hydrolysis, maltose hydrolysis and determination as glucose) have been optimised. The method is highly correlated with other dextrinising power methods. The MV method involves extraction of malt in 0.5% sodium chloride at 30°C for 20 minutes followed by filtration; incubation of an aliquot of the undiluted filtrate with starch solution (pH 4.6) at 30°C for 15 min; termination of reaction with sodium hydroxide solution; dilution of sample in an appropriate buffer; hydrolysis of maltose with a specific α-glucosidase; glucose determination and activity calculation. Unlike all subsequent reducing sugar methods, the maltose value method measures a defined reaction product, maltose, with no requirement to use equations to relate analytical values back to Lintner units. The maltose value method is the first viable method in 130 years that could effectively replace the 1886 Lintner method.

Background: The level of available carbohydrates in our diet is directly linked to two major diseases; obesity and Type II diabetes. Despite this, to date there is no method available to allow direct and accurate measurement of available carbohydrates in human and animal foods. Objective: The aim of this research was to develop a method that would allow simple and accurate measurement of available carbohydrates, defined as non-resistant starch, maltodextrins, maltose, isomaltose, sucrose, lactose, glucose, fructose and galactose. Method: Non-resistant (digestible) starch is hydrolysed to glucose and maltose by pancreatic α-amylase and amyloglucosidase at pH 6.0 with shaking or stirring at 37°C for 4 h. Sucrose, lactose, maltose and isomaltose are completely hydrolyzed by specific enzymes to their constituent monosaccharides, which are then measured using pure enzymes in a single reaction cuvette. Results: A method has been developed that allows the accurate measurement of available carbohydrates in all cereal, vegetable, fruit, food, and feed products, including dairy products. Conclusions: A single-laboratory validation was performed on a wide range of food and feed products. The inter-day repeatability (%RSDr) was <3.58% (w/w) across a range of samples containing 44.1 to 88.9% available carbohydrates. The LOD and LOQ obtained were 0.054% (w/w) and 0.179% (w/w), respectively. The method is all inclusive, specific, robust and simple to use. Highlights: A unique method has been developed for the direct measurement of available carbohydrates, entailing separate measurement of glucose, fructose and galactose; information of value in determining the glycemic index of foods.

Most commonly used methods for the measurement of starch in food, feeds and ingredients employ the combined action of α‐amylase and amyloglucosidase to hydrolyse the starch to glucose, followed by glucose determination with a glucose oxidase/peroxidase reagent. Recently, a number of questions have been raised concerning possible complications in starch analytical methods. In this paper, each of these concerns, including starch hydrolysis, isomerisation of maltose to maltulose, effective hydrolysis of maltodextrins by amyloglucosidase, enzyme purity and hydrolysis of sucrose and β‐glucans have been studied in detailed. Results obtained for a range of starch containing samples using AOAC Methods 996.11 and 2014 .10 are compared and a new simpler format for starch measurement is introduced. With this method that employs a thermostable α-amylase (as distinct from a heat stable α-amylase) which is both stable and active at 100°C and pH 5.0, 10 samples can be analysed within 2 h, as compared to the 6 h required with AOAC Method 2014.10.

Many of the enzymatic test kits are official methods of prestigious organisations such as the Association of Official Analytical Chemicals (AOAC) and the American Association of Cereal Chemists (AACC) in response to the interest from oenologists. Megazyme decided to use its long history of enzymatic bio-analysis to make a significant contribution to the wine industry, by the development of a range of advanced enzymatic test kits. This task has now been successfully completed through the strategic and comprehensive process of identifying limitations of existing enzymatic bio-analysis test kits where they occurred, and then using advanced techniques, such as molecular biology (photo 1), to rapidly overcome them. Novel test kits have also been developed for analytes of emerging interest to the oenologist, such as yeast available nitrogen (YAN; see pages 2-3 of issue 117 article), or where previously enzymes were simply either not available, or were too expensive to employ, such as for D-mannitol analysis.

It is without doubt that testing plays a pivotal role throughout the whole of the vinification process. To produce the best possible quality wine and to minimise process problems such as “stuck” fermentation or troublesome infections, it is now recognised that if possible testing should begin prior to harvesting of the grapes and continue through to bottling. Traditional methods of wine analysis are often expensive, time consuming, require either elaborate equipment or specialist expertise and frequently lack accuracy. However, enzymatic bio-analysis enables the accurate measurement of the vast majority of analytes of interest to the wine maker, using just one piece of apparatus, the spectrophotometer (see previous issue No. 116 for a detailed technical review). Grape juice and wine are amenable to enzymatic testing as being liquids they are homogenous, easy to manipulate, and can generally be analysed without any sample preparation.

The artichoke powder (AP) from the outer bracts artichokes cv Romanesco, was analyzed for its bioactive compounds, revealing its potential as a functional food ingredient. The main phenolic compounds identified were mono- and di-caffeoylquinic acids, followed by flavonoids such as apigenin and its glycosylated forms, and fiber, including inulin (~2 g/100g). AP was substituted to wheat flour at 5, 10, and 15 g/100 g to enhance bread's nutritional profile, with the 10% formulation (AB10) resulting the best balance of bioactive content, technological, and sensory properties. AB10 underwent in vitro digestion to evaluate phenolic compounds bioaccessibility, focusing on free and bound phenols, and the colon availability index (CAI), predicting intestinal absorption. Among the identified compounds, chlorogenic acid and di-caffeoylquinic acids were the most bioaccessible (92.5%), followed by apigenin-7-O-glucoside, which presented the highest CAI (26.5%). Nutritional analysis of AB10 showed a lower glycaemic index than the control, and its high fiber content (>6 g/100g) classified it as a HIGH-FIBER product. Cellular antioxidant activity assays on Caco-2 cells confirmed the scavenging capacity of AP and AB10. These findings highlight that artichoke bracts, a by-product of processing, are rich in bioactive compounds and fiber, making them valuable functional ingredients for various industrial applications, contributing to a circular economy approach.

Starch–lipid complexes have attracted widespread attention owing to high anti-digestibility and thermal stability. However, methods to increase the content of starch-lipid complexes are limited. Therefore, this study aims to investigate the effect of atmospheric cold plasma (ACP) treatment for different times (0, 1, 3, 5, and 7 min) on the formation and structure of complexes between maize starch (MS) and lauric acid (LA). The results showed that the amylose content of MS increased from 18.44% to 31.01% after ACP treatment. Moreover, structural characterization of complexes revealed that short-term ACP treatment (1 min) favored the formation of MS–LA complexes, resulting in a better V-type crystalline structure (14.90%) and short-range ordered structure (0.793) with higher thermal stability (4.47 J/g) and no obvious morphological differences. In addition, the resistant starch content of MS-LA complexes increased from 30% to 33% in MS treated with ACP for 1 min. This may be because the active substances in ACP depolymerized starch, destroyed α-1,6 glycosidic bonds, broke branch chains, and increased amylose content, which promoted the formation of complexes to a certain extent. This study proposes a method to promote the formation of starch-lipid complexes, broadening potential application of complexes in low-GI food, stabilizer, and microcapsule carrier.

This study investigated the sensory qualities and digestibility of traditional Chinese dried sweet potatoes (Gān Shŭ Gān) and identified the impact factors. Dried sweet potatoes prepared with orange-fleshed cultivars, particularly cultivars Pushu32 and Yanshu25, were preferred for their reddish hue compared to those prepared with the yellow-fleshed reference cultivar Zheshu33. The dried sweet potato made of those cultivars also provided better sensory experience mainly due to their higher chewiness. The estimated glycemic indexes (eGI) of dried sweet potato samples ranged from 78.50-99.49, with the sample prepared with Pushu32 exhibiting the lowest value. Correlation analysis and principal component analysis based on starch characteristics indicated that higher amylose content resulted in better sensory experience and more amylopectin longer chains (DP ≥ 25) contributed to lower digestibility. Both of amylose and amylopectin longer chains in sweet potato starch favored the stability of the paste. Additionally, larger starch granules in sweet potato were also conducive to lowering the eGI in dried products. These findings provided helpful insights for selecting raw materials in dried sweet potato processing.

Background and Objectives: This study aimed to investigate the noodle-making potential of oat starch and how addition of chemically modified oat starch affects quality and digestibility. An oat starch noodle preparation method was optimized and subsequently used for substituting varying levels of native oat starch (NOS) with citrate-modified oat starch (COS) (15%, 20%, 25%, and 30%). Findings: Results indicated that NOS noodles showed similar cooking loss, cooking time, and color to commercial rice noodles. Significant differences emerged between COS and NOS noodles concerning cooking time, adhesiveness, and color values. Noodles with a 25% substitution of COS demonstrated favorable quality characteristics. In terms of in vitro digestibility, noodles with COS substituted at 25% of NOS released the least amount of glucose over the 300-min digestion period compared to NOS and commercial noodles. Conclusions: The partial replacement of NOS with COS significantly reduced the cooking time of noodles without affecting their adhesiveness and color compared to NOS-only noodles. Furthermore, the in vitro digestion experiments showed that partial substitution of NOS with COS results in lower glucose release than NOS-only noodles, which is desirable for the management of postprandial blood glucose levels.

Type III resistant starch (RS3) is an important functional food ingredient. In this study, RS3 was prepared by retrogradation of pea starch after acid hydrolysis and pullulanase debranching. Heat-moisture treatments, including annealing (90°C, 40–70% moisture content) and pressure heating (121°C, 10-40% moisture content), were employed to further enhance the RS content of pea RS3. The relationship between the structural changes and digestibility of pea RS3 was investigated. The results showed significant increases in relative crystallinity, particle size, gelatinization temperature, and RS content, while swelling power, pasting viscosity, and rapidly digestible starch content were markedly decreased after heat-moisture treatment. A strong positive correlation (r = 0.94*) was observed between relative crystallinity and RS content. The highest RS content of 85.6% was achieved after pressure heating at 20% moisture content, which was notably higher than the 45.6% RS content before heat-moisture treatment. This study highlights the beneficial effects of annealing and pressure heating in enhancing RS content in pea RS3, providing valuable insights for developing RS3 with high RS content after cooking.

The fashion industry has faced increasing criticism for its unsustainable practices and needs to transition towards more circular models where renewable resources are used, and materials and chemicals are recycled. This study focuses on abundantly available mixed cellulosic wastes: mixed textile, agricultural residues and municipal solid waste, whereby half of the cellulose from the waste is converted through a hydrolytic process and fermentation into bacterial cellulose. Using ionic liquids, the feasibility of spinning the waste-derived cellulose produced into regenerated cellulose fibres with mechanical properties comparable to viscose is achieved. Furthermore, the sustainability of this approach is validated by comparing the environmental impact of the process with the impact of producing wood dissolving pulp, which is currently used to make viscose. The possibility of a biological recycling process for mixed cellulosic wastes that could complement textile mechanical or chemical strategies is discussed, but further work will be needed to validate its economic viability and sustainability at the scale required to replace feedstock used in regenerated cellulose production. The biobased and chemical approach to textile manufacturing described here is circular, supports textile-to-textile recycling offering a potential solution to textile waste management and a promising pathway for the industry to achieve its environmental goals.

To uncover the variation patterns of the nutritional components in sweetpotato storage roots during long-term storage comprehensively, the general nutrients, phytochemicals, and starch properties of nine sweetpotato varieties with different flesh colors were quantified and analyzed by chemical and physical techniques. During the storage, the starch content decreased firstly and then increased, with sugar content the opposite. The crude protein content and the total dietary fiber content both increased continuously. The β-carotene content decreased or kept constant, while the anthocyanin content showed different variation patterns in the three purple-fleshed varieties. The four types of polyphenols and two types of flavonoids showed no obvious content changes during the storage. The amylose contents of all varieties showed various patterns, while the crystallinity was C-type. The proportion of small-sized starch granules reduced, and the combined proportion of medium-sized and large-sized granules increased. New correlations among the nutritional parameters for each variety were revealed for the first time. Principal component analysis indicated that the orange-fleshed varieties were distinguished from other varieties. Finally, the most storage-resistant variety ZZ3 and the suitable variety for each quality trait was selected. This study provides not only theoretical basis for comprehensive understanding of the nutrient's variations in sweetpotato storage roots during long-term storage, but also guidelines for evaluation of nutritional quality of sweetpotato roots during storage and improvement of storage methods.

Despite being an effective and clean-label method, heat-moisture treatment (HMT) is not commonly used for starch modification in industry due to the difficulty of scale-up. This study aimed to develop a novel method of using extrusion combined with high-temperature drying (EHTD) as an alternative to HMT for starch modification. Pea starch was subjected to extrusion at 37.5% moisture level and with a low-temperature profile (≤ 65 °C), followed by immediate heating at 130°C for 1 h. EHTD significantly damaged the granules, altered the X-ray diffraction pattern, and reduced the relative crystallinity of pea starch. Overall, EHTD-modified pea starch exhibited increased gelatinization temperatures and decreased gelatinization enthalpy change, lowered pasting viscosity and gel hardness, as well as enhanced enzymatic resistance than the native pea starch. More importantly, in a human feeding trial (n = 20 healthy participants) to monitor plasma glucose response over a period of 2 h after consuming water-boiled sample (35 g starch, dry basis), EHTD-modified pea starch exhibited 22% reduction (p < 0.01) in plasma glucose incremental area under the curve as compared to the native counterpart. The results indicated that EHTD could be a new simple and clean-label method to produce functional and low-glycemic starch ingredients.

Legume-based sourdough is gaining momentum. This study aimed to compare the effectiveness of type I sourdough prepared with durum wheat semolina (S1), pea flour (S2) or 50:50 semolina/pea flour (S3) in improving the nutritional quality, antioxidant compounds, in vitro digestibility and aroma of traditional durum wheat focaccia. Six focaccias were prepared: three with 40 % of S1, S2 and S3, and three with the corresponding amount of unfermented flours. Pea sourdough increased the content of phenolic compounds (8.82 ± 0.12 mg GAE/g d.m. in focaccia with 40 % pea flour and 4.92 ± 0.41 mg GAE/g d.m. in unfermented semolina focaccia), and consequently increased the antioxidant activity. Focaccias with pea flour or pea sourdough were “source of protein” and “high fiber”, according to UE Reg. 1924/2006. Pea sourdough slowed down starch in vitro digestibility while enhancing protein digestibility and leading to a more complex volatile profile, with increased content of aldehydes, alcohols and Maillard reaction compounds.

Dextran is an exopolysaccharide (EPS) with multifunctional applications in the food and pharmaceutical industries, primarily synthesized from Leuconostoc mesenteroides. Dextran can be produced from dextrin through Gluconobacter oxydans fermentation, utilizing its dextran dextrinase activity. This study examined how jar fermentor conditions impact the growth and enzyme activity of G. oxydans, with a focus on the effects of pH on dextran synthesis via bioconversion (without pH control, pH 4.5, and pH 5.0; Jp-UC, Jp-4.5, and Jp-5.0). After 72 h, the cell density (O.D. at 600 nm) was 7.2 for Jp-4.5, 6.5 for Jp-5.0, and 3.7 for Jp-UC. Flow property analysis, indicating dextran production, showed that Jp-4.5 had the highest viscosity (30.99 mPa·s). ¹H-NMR analysis confirmed the formation of α-1,6 glycosidic bonds in bioconversion products, with bond ratios ranging from ~1:0.17 to ~1:2.84. The distribution of molecular weights varied from 1.3 × 10³ Da to 5.1 × 10⁴ Da depending on pH. The hydrolysis rates to glucose differed with pH, with the slowest rate at pH 4.5 (53.96%). These results suggest that the production of dextran by G. oxydans is significantly influenced by the pH conditions. This dextran could function as a slowly digestible carbohydrate, aiding in postprandial glycemic regulation and mitigating chronic metabolic diseases like diabetes.