Abstract
The influence of roasting conditions on the potato starch (PS) composition, solubility, crystallinity, gel-forming thermal profiles, and texture of the corresponding gels was studied. Thermorheological testing of roasted starches with (RPS) and without (RPSI) the soluble fraction was conducted on a stress-controlled rheometer. Texture profile analysis (TPA) was used to determine the RPS final gel texture. Solubility tests showed equivalent effects of starch roasting for samples treated at 190°C for 8 h (RPS190-8), 210°C for 6 h (RPS210-6), and 230°C for 4 h (RPS230-4). The apparent amylose content of RPS linearly increased with the decreasing degree of crystallinity. Elastic (G′) and viscous (G″) properties of RPS depended markedly on apparent amylose content and crystallinity. G′gel values of roasted starches linearly increased with the amylose content suggesting a promotion of the amylose breakdown with roasting temperature. Gels prepared with RPS roasted between 120 and 170°C exhibited intermediate strength and fully thermal reversible features. Roasting between 190 and 210°C favoured strong and fully thermal reversible gels. Although RPS230-4 gels exhibited similar strength to RPS190-8 and RPS210-4, no fully thermal reversible gels were obtained. The soluble fraction removal led to a drop the RPSI gels strength with increasing roasting temperature. No water syneresis was identified for RPS gels during one-week ageing, except for RPS230 gels. Relationships between textural parameters from TPA and viscoelastic gel properties determined by rheology were established.
Highlights
Potato starch (PS) is one of the most used biopolymers for industrial starch production, since the extraction procedure is simple in comparison to cereal starches [1]
It should be indicated that physicochemical features, the forming profiles of the gels, and the rheological and textural characteristics of the final gels for potato starch systems strongly depend on the roasting starch conditions
The largest physicochemical, rheological, and textural differences were identified between RPS170 and RPS190 systems
Summary
Potato starch (PS) is one of the most used biopolymers for industrial starch production, since the extraction procedure is simple in comparison to cereal starches [1] This starch gains attention by its relatively low price, gluten-free features, abundance, and its renewable and biodegradability characteristics [2]. Native and modified starches have been used as thickening agents in food processing [5] or in screen printing on textile [6], as glue in the adhesive industry [7], and as binding agents in pharmaceutical [8]. It should be remarked that these starch modifications require present industrial disadvantages from the economical point of view since these require thermal energy (expensive) and long-time processing. Achieving optimal temperature-time (i.e., energy consumption) operating conditions, depending on the properties required, is an important aspect for the industry
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