مطالعه خصوصیات عملکردی و رفتار بیاتی نشاسته طبیعی گندم در حضور صمغ دانه شاهی و ساکارز

در این پژوهش، اثر سطوح جایگزینی صمغ دانه شاهی (0، 5، 10 و 15%) و ساکارز (0، 5 و 10%) بر خصوصیات عملکردی (قدرت تورم و حلالیت) سوسپانسیون نشاسته و همچنین ساختمان، کنتیک بیاتی و آب‌اندازی ژل نشاسته گندم پس از نگهداری به مدت صفر، 1، 7 و 14 روز در دمای oc 4 مورد مطالعه قرار گرفتند. قدرت تورم نشاسته گندم با افزایش غلظت جایگزینی صمغ و قند به ترتیب افزایش و کاهش یافت. نمونه‌های مخلوط سه جزئی نشاسته-صمغ-قند دارای قدرت تورم بالاتری در مقایسه با نمونه نشاسته و مخلوط نشاسته-قند داشتند. میزان حلالیت نشاسته با افزایش غلظت صمغ و قند افزایش یافت و نمونه‌های مخلوط دارای مقادیر حلالیت بالاتری نسبت به هر یک به صورت مجزا بودند. تصاویر میکروسکوپی نشان دادند که حضور صمغ منجر به ایجاد ساختمان متراکم‌تر با اندازه حفرات کوچک‌تر ژل نشاسته شد، در‌حالی ‌که حضور قند ساختمانی گسسته‌تر با اندازه حفرات بزرگ‌تری را ایجاد کرد. پس از نگهداری نمونه‌های ژل به مدت 14 روز در دمای oc 4 مشاهده شد که افزودن صمغ تاثیر بسزایی در کاهش سرعت بیات ‌شدن و میزان آب‌اندازی نشاسته به ترتیب از (s-1) 0/101 به 0/52 و از 50% به 23% داشت. قند نیز منجر به کاهش سرعت بیات ‌شدن ژل نشاسته تا (s-1) 0/096 شد، اما میزان آب‌اندازی آن را تا 57% افزایش داد. نمونه‌های ژل مخلوط به خصوص در غلظت 15% جایگزینی صمغ دارای سرعت بیات‌شدن (s-1) 0/057 و میزان آب‌اندازی 45% بودند.

study of the functional properties and the retrogradation behavior of native wheat starch in the presence of cress seed gum and sucrose

introduction wheat starch granules are composed of amylose and amylopectin, which are responsible for the functions of starch such as swelling, gelatinization, pasting, gel formation, and retrogradation. the retrogradation changes the functional properties, it is an undesirable phenomenon in some starch-based foods which reduces the acceptability of food, and shortens the shelf life. delaying or preventing of starch retrogradation is a major challenge in the food industry. various ingredients such as carbohydrates imply an important role in improving the functional properties, decreasing amylose leaching and retarding the retrogradation of starch gels. cress seed gum (csg), as an emerging galactomannan, has shown the ability to improve the textural and rheological features of food systems based on its unique properties. addition of csg to the composite wheat-rice bread increased dough stability and improved the staleness of bread compared to guar gum. also, the addition of csg and xanthan gum to gluten-free bread stabilized the texture of bread during storage. sucrose (suc) is a common additive in food formulations which is useful as a sweetening agent and textural modification. sugars have been able to reduce amylose leaching and accelerate or delay starch gel formation. they also delay retrogradation of starch gels during storage. therefore, the objectives of this study were to determine the impact of different substitution levels of csg (0, 5, 10 and 15%), suc (0, 5 and 10%), and their blend on the functional properties (swelling strength and solubility), microstructure features, retrogradation kinetics and synthesis of native wheat starch (nws) gel (4% w/w).materials and methods cress seeds were purchased from a local medicinal market. nws and suc were supplied from sigma aldrich (spain) and merck (germany) respectively. starch suspensions (0.6 gr powder/20 ml water) substituted with csg (0, 5, 10, and 15% w/w) and suc (0, 5, and 10% w/w) were prepared to estimate the swelling power and solubility index. to produce starch gel, the 4% w/w suspensions of nws-csg-suc were prepared by dissolving the appropriate amount of csg powder and suc in deionized water. then, each suspension was poured into a stainless-steel cylindrical container and was heated to 95 oc and held at 95 oc for 3 min and then cooled to 50 oc while stirring continuously at 160 rpm with a mechanical mixer. finally, the pastes were kept at ambient temperature (25 oc) for 1 h. to assess gel structure, imaging of the gels was performed by scanning electron microscopy (sem). the retrogradation kinetics and syneresis of gel samples were determined after storage at 4 oc for 0, 1, 7 and 14 days.results and discussions the swelling power and solubility index of nws increased with increasing the replacement level of csg. csg promotes adhesive interactions among the gelatinized granules. this can enhance the forces applied to them, facilitating water entering (increasing swelling), amylose solubilization and its exudation. in contrast, suc compete with starch molecules for water in the system and thus preventing gelatinization and mobility of starch molecules reduced the swelling power. the starch-gum-sugar mixtures had a higher swelling power compared to the starch and starch-sugar samples. the mixed samples had higher solubility values than each of them individually. sem images showed that the pore size of starch gel decreased and increased from 33.01 to 29.44 µm and to 45.37 µm with increasing the substitution levels of csg and suc, respectively. nws-15% csg-5% suc gel had 31.34 µm pore size.