Dynamic rheology of structure development in low-methoxyl pectin+Ca2++sugar gels1

Sucrose and Ca2+ synergistically regulate the rheological properties of apple high-methoxyl pectin

The thickening and gelling mechanism of high-methoxyl pectins (HMPs) with different degree of esterification (DE) values (60.6 %, 66.1 %, and 72.4 %) synergistically affected by calcium ion (Ca2+) and sucrose was investigated using several technical methods. Rheological measurements, including steady-shear flow, thixotropy and dynamic viscoelasticity tests, texture analysis, water-holding capacity (WHC), thermal analyses (TG), and microstructure observation (TEM), were all systemically conducted. The results showed that the main thickening and gelling mechanism of Ca2+ on different HMPs was complex and the presence of sucrose had a synergistic effect on structure formation in HMP systems. Ca2+ was not always conducive to structure formation, and excessive Ca2+ addition may hinder structure formation. HMP systems with lower DE values had higher gel strengths due to the presence of more binding domains. The results of the texture properties, WHC, and thermal characteristics coincided with those obtained from the rheological measurements, which reflect the variations in HMPs affected by Ca2+ and DE. All of these results showed that Ca2+ addition at an appropriate concentration in the presence of sucrose favors HMP gelation even in the absence of acid. The results obtained here are expected to broaden the application of HMPs in acid-free gel food products.

Use of natural low-methoxyl pectin from sunflower by-products for the formulation of low-sucrose strawberry jams

BACKGROUND

Due to the increasing incidence of obesity and cardiovascular diseases, consumers are demanding products with lower sugar content. In this sense, the reformulation of traditional foods with improved, safe and tasty ingredients is arousing a huge interest. Jams are conventionally produced with elevated amounts of sucrose, which increase the glycaemic index and must be avoided in certain kinds of consumers.

RESULTS

This paper describes for the first time the elaboration of strawberry jams using low-methoxyl pectins from sunflower by-products, which allowed the addition of low amounts of sucrose (10-30%). These jams were compared with best-selling commercial samples. An in-depth physicochemical, compositional, sensorial and rheological characterization was carried out. The obtained jams were safe considering a_w and pH values; samples presented enough acidity to avoid microorganism development and syneresis. The stabilizing role of sunflower pectin is noteworthy in terms of colour and other physicochemical characteristics. The organoleptic analysis showed that the taste and sweetness of laboratory samples were highly valued, although the presence of pieces of fruits was disliked some panellists. After knowing the content of added sugar used in each jam, the tasters preferred samples with 20% and 30% of sucrose over commercial samples.

CONCLUSIONS

The results show the usefulness of sunflower pectin for the elaboration of jams of low glycaemic index. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Advances and prospects in the food applications of pectin hydrogels

Pectin hydrogel is a soft hydrocolloid with multifaceted utilities in the food sector. Substantial knowledge acquired on the gelation mechanisms and structure-function relationship of pectin has led to interesting functions of pectin hydrogel. Food applications of pectin hydrogels can be categorized under four headings: food ingredients/additives, food packaging, bioactive delivery and health management. The cross-linked and tangly three-dimensional structure of pectin gel renders it an ideal choice of wall material for the encapsulation of biomolecules and living cells; as a fat replacer and texturizer. Likewise, pectin hydrogel is an effective satiety inducer due to its ability to swell under the simulated gastric and intestinal conditions without losing its gel structure. Coating or composites of pectin hydrogel with proteins and other polysaccharides augment its functionality as an encapsulant, satiety-inducer and food packaging material. Low-methoxyl pectin gel is an appropriate food ink for 3D printing applications due to its viscoelastic properties, adaptable microstructure and texture properties. This review aims at explaining all the applications of pectin hydrogels, as mentioned above. A comprehensive discussion is presented on the approaches by which pectin hydrogel can be transformed as a resourceful material by controlling its dimensions, state, and rheology. The final sections of this article emphasize the recent research trends in this discipline, such as the development of smart hydrogels, injectable gels, aerogels, xerogels and oleogels from pectin.

Complex formation of a 4-α-glucanotransferase using starch as a biocatalyst for starch modification

A 4-α-glucanotransferases from Thermus thermophilus (TTαGT) possesses an extra substrate binding site, leading to facile purification of the intact enzyme using amylose as an insoluble binding matrix. Due to the cost of amylose and low recovery yield, starch was replaced for amylose as an alternative capturer in this study. Using gelatinized corn starch at pH 9 with 36-h incubation in the presence of 1 M ammonium sulfate increased the TTαGT-starch complex formation yield from 2 to 56%. In preparative-scale production, TTαGT produced in Bacillus subtilis was recovered by 42.1% with the same specific activity as that of purified TTαGT. Structural and rheological analyses of the enzymatically modified starches revealed that the starch complex exhibited catalytic performance comparable to soluble TTαGT, suggesting that the starch complex can be used as a biocatalyst for modified starch production without elution of the enzyme from the complex.

Polissacarídeos extraídos da gabiroba (Campomanesia xanthocarpa Berg): propriedades químicas e perfil reológico

A Campomanesia xanthocarpa Berg (Myrtaceae) é uma frutífera nativa brasileira, com ampla distribuição natural na região Sul. Embora apresente frutificação abundante, produza frutos com características sensoriais e nutricionais atrativas, esses não são coletados e se perdem nos campos. Neste trabalho, a polpa do fruto sem semente (1500 g) foi triturada em etanol / água na proporção de 1:4 (v/v), refluxada por 15 minutos em temperatura de ebulição. O resíduo obtido foi submetido a extrações sequenciais. As extrações foram otimizadas utilizando um planejamento fatorial 2², tendo como variáveis a concentração do ácido cítrico (0,5 e 5%) e a temperatura (50 e 100 ºC). Os polissacarídeos provenientes de diferentes extrações foram caracterizados quanto à composição química e perfil reológico. Os altos teores de ácidos urônicos, arabinose e galactose detectados em todas as frações, indicam que estas são constituídas por polissacarídeos pécticos. Os polissacarídeos extraídos da polpa da gabiroba apresentaram um comportamento pseudoplástico. Todas as frações apresentaram como característica resistência frente às variações de temperatura. Quando submetidas a ciclos de aquecimento e posterior resfriamento estes géis retornam à sua estrutura original.

Pectin Extraction from Lemon By-product with Acidified Date Juice: Rheological Properties and Microstructure of Pure and Mixed Pectin Gels

The microstructure and the rheological properties of lemon-pectin mixtures were studied and compared to those of pure lemon (high methoxyl: HM) and date (low methoxyl: LM) pectins. Rheological properties were carried out in the presence of 30%, 45% and 60% sucrose, and increasing calcium concentrations (0-0.1%). The presence of date with lemon pectin led to a gel formation at 45% sucrose and in the presence of calcium, which was not the case for lemon pectin alone under the same conditions. It is suggested that lemon and date pectins interacted, leading to gel formations at different gelling temperatures, which were strongly dependant on degree of methylation. These results were confirmed by scanning electron microscopy, which revealed inhomogeneous gels where dense aggregated network and loose, open network areas were present. Addition of calcium to pectin mixture gels led to stronger and faster gel formation.