Coronell-Tovar, Diana C.

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    Elaboración de harina a partir del cormo de la yautía (Xanthosoma a spp.) del cultivar nazareno con potencial uso en la industria de alimentos
    (2015) Coronell-Tovar, Diana C.; López-Moreno, Martha L.; College of Agricultural Sciences; Orellana-Feliciano, Lynette E.; Chávez-Jauregi, Rosa N.; Rivera-Serrano, Aixa; Department of Crops and Agro-Environmental Sciences; Torres-López, Ramòn
    The Nazareno cultivar of the cocoyam root crop (Xanthosoma spp.) is a new hybrid that retains the best properties of this specie. Therefore, it is desirable to take advantage of the whole major storage organs, primordially the whole corm (central stem), which constitutes most of the plant’s body. However, the corm cannot be consumed in its natural form given its high calcium oxalate content, which represents an antinutritional factor that imparts acridity and an astringent- sour taste. The goal of the present study was to develop a multipurpose flour of this cultivar as a means to provide a value-added option as well as a potential flour alternative in the food industry. The corms were planted in the Agriculture Experimental Station at Isabela, harvested after 10 months and subsequently processed in the pilot plant of the Food Science and Technology Program of the University of Puerto Rico at Mayagüez. These were divided in three sections (distal, middle and apical), peeled, cut, dehydrated and milled. The flour was submitted to three physical processes including soaking in water, sun-drying and boiling to reduce the oxalate content, which was quantified by permanganometry. The process that proved most effective was soaking in distilled water for 72 h at 28 °C in constant shaking, providing a 77 % oxalate reduction. Taking into account the efficiency of the soaking process, flour was produced in large scale. Several physical properties were assessed such as true and bulk density, porosity, water activity (aw), and whiteness index. The study also encompassed different chemical properties including proximate composition, dietary fiber, reducing sugars, pH, starch by spectrophotometry, amylose and amylopectin by high performance size exclusion chromatography (HPSEC), minerals by inductively coupled plasma optical emission spectrometry (ICP-OES), saponins, phytates and tannins and oxalate by permanganometry. Similarly, functional properties were evaluated such as water and oil absorption, water solubility index, emulsifying capacity, gelatinization profile by differential scanning calorimetry (DSC) and pasting profile by viscometry. Additionally, sorption isotherms were determined at three different temperatures (10, 25 and 40 °C) and the microbial stability was assessed during a 9-month period of storage at room temperature. Two products were developed and the level of acceptance was evaluated by means of sensory analysis. Results suggest that the soaked cocoyam flour has a high dietary fiber content (15.4 % insoluble fiber and 2.8 % soluble fiber) and is essentially energy-rich given its high starch content (60.5 %), where 85.04 % is amylopectin. The most abundant minerals were potassium (19.09 mg/g), calcium (2.53 mg/g) and phosphorus (2.01 mg/g). The antinutritional content analysis showed low levels for saponins (0.10 %) and tannins (0.07 %), while levels of phytates were not detected. The flour showed a low emulsifying capacity (5.4 %), and a good water (9 – 11 g water/g flour at 90 and 100 °C) and oil (1.2 g water/g flour) absorption capacity. The gelatinization temperature of the flour was high, ranging from 81.81 to 89.58 °C. The flour paste was stable during heating (breakdown = 2.30 RVU) and unstable during cooling (setback = 35.14 RVU). The Double Log Polynomial (DLP) model was the one that best adjusted to the sorption isotherms (R2 > 0.99). The moisture content (6.55 %) and aw (0.35) were both low, producing unfavorable conditions for microbial proliferation. This could explain the high microbial stability observed after being stored for 9 months at room temperature. The sensory tests for both cookies and soups revealed a high level of general acceptance with scores ranging between 7 and 8 (“I like it moderately” and “I like a lot”) based on a 9-point hedonic scale. Furthermore, the versatility of the flour was evident in other preparations including pasta, sauces and crêpes. Consequently, the cocoyam flour represents a raw material suitable for human consumption with a great potential in the food industry for the elaboration of different products, turning it into a value‒added food product and thus, an economically feasible alternative for farmers that harvest this root crop in Puerto Rico.