Ultrasound‐Assisted Extraction of Lychee (Litchi chinensis Sonn.) Seed Starch: Physicochemical and Functional Properties

Abstract

High-power ultrasound (HPU) is a non-thermal processing method that has been researched and used in the last years. The application of ultrasound can modify and improve some technologically important compounds such as starch. This research aimed to examine the effect of ultrasound treatment on yield, physicochemical, and functional properties of lychee seed starch (LS). HPU experimental conditions used were sonication time (5 and 20 min) and amplitude (40% and 70% ). Starch yield significantly increased with increasing ultrasound amplitude and time. The ultrasound did not change the morphology and shape of the granules but caused cracks in their surface. Surface damage induced an increase in amylose content, relative crystallinity, enthalpy of gelatinization, swelling power, solubility index, and acid hydrolysis of the starch. These results indicate that ultrasound mainly affected the amorphous starch region. The morphology, size, color, rheological and thermal characteristics, crystal structure, and structural order features of the untreated and ultrasound-treated LSs were compared. A principal component analysis was carried out to assess the effect of the ultrasound treatment on LS characteristics.

The Effect of Starch Isolation Method on Morphological and Physicochemical Properties of Zagros Oak (Quercus brantii var. Persica) Starch

“…[ 44,45 ] It was reported that the cavitation can break intermolecular bonds of starch and decrease its yield. [ 46 ] However, Morales‐Trejo et al showed the ultrasonic treatment (alkaline extraction method + ultrasonic in 40% and 70% amplitude in 5 and 20 min) significantly increased the Lychee starch yield and by increasing amplitude and time the yield was also increased [ 17 ] due to the mechanical action of sonication which led to cell wall disruption. [ 47 ]…”

“…The amylose content affects the technological and functional properties of starch including gelatinization, recrystallization (retrogradation), solubilization, swelling, viscosity and texture, and the formation features. [ 17 ] The amylose content of starch samples isolated by various methods is shown in Figure 1B. The range of amylose content was between 17.7% (LAE‐C) and 18.13% (EAE‐A).…”

“…Furthermore, previous researches suggested that ultrasonication can increase the amount of amylose content due to the mechanical effect of sonication and molecular scission of amylopectin chains. [ 17,44 ] However, for Zagros acorn the positive effect of ultrasound on amylose content was not proved. Moreover, the results showed that different levels of each treatment did not have any significant effect on the amylose content.…”

“…It was suggested that the complex of amylose‐lipid or amylose‐iodine can also disrupt the actual estimation of amylose content. [ 7,9,17,50 ]…”

“…can obtain raw materials with special features for new and specific applications without a requirement of chemical and genetic modification. [ 17 ] Moreover, starch extraction contributes to preserve oak forests and obtain some valuable by‐products such as polyphenolic compounds, tannin, and oil. [ 18 ] However, limited studies have been conducted on the extraction and characterization of starches isolated from new and nonconventional sources.…”