Influence of drying temperature on physico-chemical and techno-functional attributes of elephant foot yam (Amorphophallus paeoniifolius) var. Gajendra

doi:10.1016/j.fbio.2016.07.004

Food Bioscience

Volume 16, 1 December 2016, Pages 11-16

https://doi.org/10.1016/j.fbio.2016.07.004 Get rights and content

Abstract

Elephant foot yam is a salubrious but underutilized tuber. Being rich in starch as well as various bio-actives (phenolics), it offers dual-functionality. The study was undertaken to obtain Amorphophallus flour that can be utilized in various food applications. Pre-cooked Amorphophallus paste was dried in convective air dryer at varying temperatures (50, 60 and 70 °C) and milled into a powder. The powders were then analyzed for physico-chemical and techno-functional aspects. Drying temperature markedly affected the color, techno-functional attributes including pasting properties, phenolic content and anti-oxidative capacity of Amorphophallus powder; the oxalate content remained unaffected by drying temperature. Decrease in whiteness index and increase in browning index were noticed with rising drying temperature. All gelatinization-viscosity parameters (peak, trough, breakdown, final and setback viscosity) showed a decline with rising drying temperature while an increasing trend was observed for pasting temperature. Significant differences were also observed in flavor and mouth-feel (p<0.05) scores of Amorphophallus-milk dispersion and were maximum for powder obtained upon drying at 60 °C. The nutritional and thickening potential of yam could very well be utilized in hybrid-dairy foods.

Introduction

Elephant foot yam (EFY) (Amorphophallus paeoniifolius (Dennst.) Nicolson), a high potential tuber, is referred to as ‘King of Tuber Crops’ because of its high yield potential, culinary properties and medicinal utility (Sengupta, Chowdhary, Singh, & Ray, 2008). The dry matter content in the tuber ranges from 17.5% to 24.0%, starch from 13.9% to 21.5%, sugar from 0.55% to 1.77%, protein from 0.84% to 2.60% and fat from 0.07% to 0.37% (Chattopadhyay, Saha, Pal, Bhattacharya, & Sen, 2010). Therapeutic uses of EFY include arsa (hemorrhoids), pliha (splenic disorders), gulma (tumor conditions), svasa (breathing disorders), kasa (cough) and asthila (prostate disorder). Its role against cytotoxic and apoptic potential against human colon carcinoma cell line HCT-15 has been proven (Ansil, Wills, Varun, & Latha, 2014). Various health and recuperative benefits of EFY have been well described by Dey, Ota, Srikanth, Jamal, and Wanjari (2012). Due to its nutritional advantages, the EFY can be consumed regularly (Sangeeta & Hathan, 2016).

Apart from aforementioned functional benefits, EFY is a rich source of starch and therefore a potential thickening agent. Starch imparts body and mouth-feel to the product (Verbeken, Baela, Thasb, & Dewettincka, 2006). It has the ability to gelatinize upon heating in the presence of water leading to increase in the viscosity. This phenomenon eventually influences the texture and stability of various foods such as sauces, cream soups, pie fillings, salad dressing, cake toppings, gum confections etc.

Since EFY has a high moisture content, drying could facilitate its easy preservation by removal of free moisture. Drying, one of the oldest and efficient preservation techniques, causes microbial spoilage to subside as water is removed (Xiao, Gao, Lin, & Yang, 2010). Additionally, drying causes a reduction in weight and volume of product, thus accounting for savings during packaging, transportation and storage. Conventionally, sun drying is preferred to obtain EFY powder, but the process is slow and uncontrolled because it is affected by weather changes. Hot air drying (tray drying) is much quicker, controlled and economically feasible drying technique that can be employed in developing nations for a better and uniform product. Hot air drying produces several physical and chemical modifications in the product i.e. color, phenolic level, anti-oxidative potential, pasting properties, sensory behavior, which are largely temperature dependent and affect the product quality. The quality of the product obtained after drying is important because minimal damage to its dual-functionality i.e. bioactive constituents (phenols), anti-oxidative potential (Vashisth, Singh, & Pegg, 2011) and pasting properties, could possibly govern the usage of EFY powder in value-added foods as well as in foods where thickening/ stabilizing potential of EFY powder is desirable. Use of EFY as an ingredient in dairy foods would be greatly facilitated if it is converted into powdered form. Convective drying of EFY has not been studied so far. Hence, the objective of the study was to assess the impact of various drying temperatures (50, 60 and 70 °C) during hot air drying on EFY powder in terms of color parameters, phenolic content, anti-oxidative potential and techno-functional properties.

Section snippets

Raw Material

Fully mature globose corms of elephant foot yam (var. Gajendra) harvested in the month of March were purchased from Navsari Agriculture University, Navsari, Gujarat, India. The EFY was washed, peeled and diced into 2×2×2 cm cubes. The cubes were immediately dipped in 0.1% potassium metabisulphite (Himedia Laboratories, Mumbai, India) solution (5 min) to prevent browning. The cubes were then blanched in boiling water (cubes:water–1:6) for 10 min, cooled, packed in nylon pouches (Hitkari Industries

Results and discussion

Drying time decreased with increasing temperature. It was shortest (~270 min) for drying at 70 °C, while the time taken at 50 °C was maximum (780 min); the drying time was 495 min at 60 °C. The moisture content of powdered EFY was 4.5–6.8%. It would be certainly desirable that the dried product obtained at different temperatures had the same moisture content. However, lack of adequate control on the drying process resulted in the moisture content vary over a relatively small range. Njintang and

Conclusion

This study has shown that drying temperature is an important factor that affects the properties of elephant foot yam (EFY) powder. Drying temperature markedly affected various aspects of elephant yam powder. Higher drying temperature caused greater browning of powder and simultaneously caused reduction in the phenolic content of the powder. Techno-functional properties were also affected, which can have significant effect when tuber/or tuber starch is included in food applications. EFY powder

Acknowledgments

The first author gratefully acknowledges the financial assistance provided by the INSPIRE-DST, New Delhi (Grant no. IF10556), in the form of a Research Fellowship and facilities provided by the Director, NDRI, Karnal, for carrying out this work.

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Starch isolated from elephant foot yam (Amorphophallus paeoniifolius) was modified by heat moisture treatment (HMT) using various heating sources viz. hot air oven (HAO), autoclave (AL), and microwave (MW). Morphology, surface roughness, thermal, structural, and dynamic rheological properties of native and HMT modified elephant foot yam starch (EFYS) were evaluated. Surface cracks, pitting, and scratching were prominent on the granules after modification, leading to an increase in surface roughness. HAO treated EFYS exhibited the highest formation of agglomerations and an increase in particle size compared to other treatments. All the modified EFYS samples had a significant increase in amylose content, and the highest was observed in HAO treatment. An increase in gelatinization temperature and reduction in gelatinization enthalpy were observed in HMT EFYS. Relative crystallinity was reduced in HMT modified EFYS which varied in the range of 35–41% as compared to native EFYS of 43%. A decrease in molecular weight from native 6.39 × 10⁷ g/mol to HMT modified EFYS was observed which varied in the range 4.51–5.37 × 10⁷ g/mol. Interestingly, the increase in elastic behavior was noticed in all modified EFYS compared to native EFYS and the highest increment was noted in HAO treated EFYS, suggesting the formation of a strong gel network under high shear. The Pearson correlation studies showed that particle size and short amylopectin chain fractions have significant positive correlation with dynamic moduli of EFYS. HMT using HAO treatment resulted in improved characteristics of EFYS and extended the range of its use in food processing.
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Citation Excerpt :
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Influence of drying temperature on physico-chemical and techno-functional attributes of elephant foot yam (Amorphophallus paeoniifolius) var. Gajendra

Abstract

Introduction

Section snippets

Raw Material

Results and discussion

Conclusion

Acknowledgments

Food Research International

Food Chemistry

Food Chemistry

Food Chemistry

Saudi Journal of Biological Sciences

LWT-Food Science and Technology

Food Chemistry

LWT-Food Science and Technology

Journal of Food Engineering

Innovative Food Science and Emerging Technologies

Food Research International

Food Chemistry

Journal of Food Engineering

LWT-Food Science and Technology

Journal of Food Composition and Analysis

Carbohydrate Polymers

Journal of Food Engineering

Food Chemistry