Textural character of sweet potato root of Korean cultivars in relation to chemical constituents and their properties

Effects of Steaming on Chemical Composition of Different Varieties of Purple-Fleshed Sweetpotato

Purple-fleshed sweetpotatoes (PFSPs) are rich in anthocyanins and are one of the health foods of interest. In this study, the effects of steaming on the anthocyanin, starch, soluble sugar, volatile organic compounds (VOCs) and pasting properties of nine PFSPs from China were investigated. The anthocyanin content of raw PFSP ranged from 9 to 185 mg/100 g. The total starch content decreased and soluble sugar content increased in all purple potatoes after steaming. Among the nine PFSPs varieties, Guangshu20 showed the greatest decrease in starch content (30.61%) and the greatest increase in soluble sugar content (31.12%). The pasting properties affected the taste of the PFSPs, with Shuangpihuang having the lowest peak viscosity (720.33 cP) and Guangzishu12 having the highest peak viscosity (2501.67 cP). Correlation studies showed that the anthocyanin content and pasting properties were negatively correlated with most of the sensory indicators, whereas the soluble sugar content of steamed PFSPs was significantly positively correlated with sweetness. A total of 54 VOCs were identified in this study, and aldehydes and terpenoids were the major VOCs in PFSPs. This study provides a theoretical basis for the processing of different PFSP varieties.

Baked sweetpotato textures and sweetness: An investigation into relationships between physicochemical and cooked attributes

Sweetpotato varieties vary greatly in perceived textures and sweetness. This study identified physicochemical factors that influence these attributes in cooked sweetpotatoes. Fifteen genotypes grown on three plots were baked and evaluated by a trained descriptive sensory analysis panel for sweetness and 13 texture attributes. Mechanical parameters were measured by texture profile analysis (TPA); and composition (starch, cell wall material, sugar contents), starch properties (thermal, granule type ratios, granule sizes), and amylase activities were characterized. TPA predicted fracturability and firmness well, whereas starch and sugar contents, B-type starch granule ratio, and amylase activities influenced prediction of mouthfeel textures. Sweetness perception was influenced by perceived particle size and sugar contents; and maltose generation during baking was highly correlated with raw sweetpotato starch content. These relationships between physicochemical sweetpotato properties and baked textures and sweetness could benefit breeders and processors in selecting biochemical traits that result in consumer preferred products.

High impacts of cultivar and home-cooking practice on the content of free myo-inositol, a bioavailable health-promoting cyclitol, in sweet potato

Free myo-inositol is a bioavailable form of a cyclitol having various health-promoting activities. The impact of cultivar and home-cooking practice on the content of free myo-inositol in sweet potatoes (12 cultivars grown in 2 different locations) was studied. A GC-MS/MS method following in situ trimethylsilylation was established and validated to determine free myo-inositol. The established analytical method was sensitive, precise, and accurate. It was found that free myo-inositol content in sweet potato varied greatly (sevenfolds) with cultivar, ranging from 377.1 to 2628.3 mg/kg dw. A cultivar Poongwon-mi was found to be an exceptionally rich source of free myo-inositol (2628.3 mg/kg dw). Home-cooking practice markedly increased free myo-inositol content (maximum 240%). Baking showed the highest impact on the increase in free myo-inositol, followed by steaming, microwave cooking, and boiling, in decreasing order. This represents the first report of the remarkably high impact of cultivar and home-cooking practice on the free myo-inositol content in sweet potato. PRACTICAL APPLICATION: The free myo-inositol content in sweet potato varied greatly with the cultivars. Poongwon-mi contained a surprisingly high content of free myo-inositol. Home-cooking dramatically increased the free myo-inositol content.

Comprehensive Evaluation of Raw Eating Quality in 81 Sweet Potato (Ipomoea batatas (L.) Lam) Varieties

The raw eating quality of sweet potato is complex. As consumers start paying more attention to the raw eating quality of tuberous roots in sweet potato, the evaluation of the raw eating quality of sweet potato is becoming an important issue. Therefore, we measured 16 quality indicators in 81 varieties of sweet potato. It was found that these 16 quality traits had different coefficients of variation (C.V.). Among them, the C.V. of fructose, glucose, and adhesiveness were the largest: 87.95%, 87.43% and 55.09%, respectively. The cluster analysis method was used to define six categories of the different tuberous roots of sweet potato. Group I, III, and IV had a stronger hardness and higher starch and cellulose content. Groups II, V, and VI were softer, with a high moisture and soluble sugar content. The principal component analysis method was used to comprehensively evaluate 16 quality indicators of 81 sweet potato varieties. It was found that Futian1, Taishu14, and Nanshu022 are good varieties in terms of raw eating quality. These varieties have low hardness, high adhesiveness in texture, high soluble sugar content, and low starch and cellulose. Future research should focus on improving the raw eating quality of sweet potato by reducing hardness, starch, and cellulose, while increasing adhesiveness, soluble sugar, and moisture content.

Relationships between isolated sweetpotato starch properties and textural attributes of sweetpotato French fries

Sweetpotato French fry (SPFF) textures have been associated with dry matter and starch contents, but these do not fully account for all textural differences. This study investigated the relationships between the physicochemical properties of sweetpotato starch and textural attributes of sweetpotato fries. Starches from 16 sweetpotato genotypes that varied in dry matter content were isolated and analyzed. The amylose content, pasting temperatures and viscosities, and textural properties of equilibrated starch gels were measured. Correlational analysis was performed with the respective SPFF mechanical and sensory texture attributes. Sweetpotato starch amylose content ranged from 17.3% to 21.1%, and the pasting and gel textural properties varied significantly between starches. Starch from orange-fleshed sweetpotatoes had lower pasting temperatures than starches from yellow/cream-fleshed genotypes, 72.2 ± 2.0 and 75.5 ± 1.1 °C, respectively. Notable inverse correlations were observed between the starch pasting temperature and perceived moistness (r = -0.63) and fibrousness (r = -0.70) of fries, whereas SPFF denseness was positively associated with starch pasting viscosity (r = 0.60) and nonstarch alcohol-insoluble solids content. Fry textures were likely affected by cooked starch properties, which should be considered when selecting varieties for sweetpotato fries. PRACTICAL APPLICATION: Without the aid of a batter, sweetpotato French fries (SPFFs) tend to be soft and limp-undesirable attributes in a fried food. The physiochemical properties of starch, the most abundant component in sweetpotato fries, were further explored in this study to better understand the properties of sweetpotato starch that influence SPFF textures. These findings can be used by sweetpotato processors and breeders for developing new sweetpotato varieties that are designed for production of fried products with desirable textures.

Isolation and physicochemical property of individual parenchyma cells from mealy sweet potato

This study prepared the dehydrated sweet potato parenchyma cell (SPPC) by isolating intact, individual parenchyma cells (PC) from sweet potato (SP) flesh using pectinase, and compared its chemical compositions, solubility and swelling power, gelatinization, and pasting viscosity to sweet potato starch (SPST) and flour (SPFL). The highest yield of SPPC was achieved when frozen SP whole-tissues were treated with pectin lyase. The majority constituting SPPC was intact, individual PCs fully filled with SPST granules. SPPC possessed lower crude protein and ash contents than SPFL. SPPC revealed lower solubility and swelling power, higher gelatinization temperatures, and lower pasting viscosity than SPST, while it showed lower solubility, higher swelling power, lower gelatinization temperatures, and higher pasting viscosity than SPFL. Overall, SPPC characteristics may result from intact PC walls surrounding clusters of SPPC granules, and SPPC could be considered an alternative to SPFL and SPST for expanding industrial applications of SP.