Postharvest Conservation of the Tuberous Roots of Pachyrhizus Ahipa (wedd) Parodi

This paper aimed to evaluate the effects of storage periods on the conservation of Pachyrhizus ahipa roots at different temperatures and packaging materials. The roots were harvested, washed, packed in PVC, plastic bags, without wrappings (control) and stored in polystyrene trays in refrigerators, or cold chambers, or at room temperature. Total titratable acidity (TTA), total soluble solids (TSS), pH, as well as their ash, lipid, total carbohydrate and protein (dry basis) contents were analyzed. The lowest loss of root fresh weight was observed in the cold chamber and plastic bags. The TTA remained higher among roots stored in the cold chamber and in PVC packaging. The lowest TSS contents were observed for roots stored in the cold chamber, and these did not vary among the packing materials. The average carbohydrate content percentage for all treatments was 84.9%. The percentage of lipids was highest in roots stored at room temperature while protein and ash contents were highest in roots under refrigeration. The best storage conditions for roots are plastic bags packaging in a cold chamber, with the roots retaining appropriate quality for commercialization for up to 30 days.


INTRODUCTION
Pachyrhizus is one of the few legume genera that have edible tuberous roots with high nutritional value and a potential for large-scale cultivation (e.g.P. erosus (L.) Urban, P. tuberosus (Lam.)Sprengel and P. ahipa (Wedd.))(Kay 1973, Sorensen et al. 1997).One of the main reasons for the increased interest in this species is its high amylopectin content, that making Andean "yam bean" ideal for the starch industry.Additionally, the protein content of the tuberous roots of P. ahipa has also stimulated commercial interest in this product, and it is highly appreciated in Europe (Sorensen et al. 1997).
Economic interest in Pachyrhizus in Mato Grosso do Sul State (Brazil) is focused on the high 761-768
starch content of its roots, which has stimulated its cultivation and consumption and contributed to the sustainable development of domestic agriculture.However, the quality of the roots must be taken into consideration for both commercialization and consumption.
Postharvest losses in Brazil for roots, rhizomes, and tubers have been estimated at 30.3%, and are generally caused by inadequate handling and storage, inappropriate packaging, and pathogens (Chitarra andChitarra 2005, Cenci 2006).Fresh weight losses of agricultural products result in size loses, wilting, as well as alterations of the food's texture, appearance, and nutritional quality, thus reducing their market acceptance (Woods 1990).Modifications of the gaseous components of the storage air can complement or even replace refrigeration, and this has become an increasingly popular technique for conserving fruits and vegetables (Chitarra and Chitarra 2005).As such, the present work evaluated the efficiency of different storage temperatures and different types of packaging on the post-harvest conservation of P. ahipa "jacatupé" roots.Five hundred P. ahipa seeds were sowed into plastic planting sacks containing sand and soil (1:1) under uncontrolled environmental conditions in a greenhouse with 50% full sunlight and daily watering; after 20 days they were transferred to planting beds to complete their development.

Seeds of
After eight months of cultivation, the "jacatupé" roots were harvested, washed under running water to remove any soil particles and were analyzed for their chemical constituents and stored in 25 × 15 cm polystyrene trays.The trays, each with 60 g of roots, were stored in a refrigerator (13°C ± 2°C and 41% RH), in a cold chamber (5°± 2°C and 70% RH), or at room temperature (30° ± 2°C and 89% RH).Three packaging techniques were used: laminated PVC (polyvinyl chloride) packages; low-density (PEBD) commercial plastic bags (20 μm of thickness); as well as open trays (without packing), as control treatments (Fig. 1).The samples were weighed every two days to determine fresh weight losses.After 30 days, when the roots were wilted and showed evidence of sprouting (characteristics that would make them unacceptable for commercialization), the experiments were terminated and samples were taken for biochemical analyses.At the end of the experimental period samples from each storage condition were submitted to biochemical analyses to determine the average values and standard deviation of the following chemical constituents: water content (by drying at 105°C); proteins (Micro-Kjeldahl method); lipids (acid hydrolyses, followed by Soxhlet extraction using petroleum ether as the solvent); ashes (obtained by incineration, followed by the heating in muffl e at 550-570°C), according to Adolfo Lutz Institute´s methods (1985).The analysis of total soluble solid content (TSS); total titratable acidity (TTA); pH; total sugar content are all according to AOAC (2005)´s patterns; and starch content (according to Dalqvist 1967).The nutritional fi ber content was quantifi ed using the enzymatic-gravimetric technique described by AOAC (2005).
The experiment was carried out with a completely randomized block design with 3 replications, of 3 (temperatures) × 3 (packages) factorial arrangement and each experimental unit with 60 g.Three of them were used for weighting and the other three, for biochemical analysis.
The data relating to fresh weight loss were submitted to variance and regression analysis (Banzato and Kronka 2006) and the averages were compared using the Tukey test at a 5% level of probability, using the SANEST program.

RESULTS AND DISCUSSION
The roots of "jacatupé" that were collected after eight months of cultivation in Mato Grosso do Sul State (MS) were much smaller than those normally harvested in São Paulo State (where their growth cycle is fi ve months), probably due to variations in the regional climatic and soil conditions.It is therefore suggested that "jacatupé" roots should be cultivated for more than 8 months in Mato Grosso do Sul State to achieve ideal size for commercialization.
The chemical characteristics of P. ahipa roots after harvesting are listed in Table I.

Characteristic Mean
TSS (° Brix) 6.9  No signifi cant relationships were observed between the packaging materials and storage environments for any characteristics evaluated.Fresh weight losses during storage at room temperature and under refrigeration were considerably higher in roots that were not packaged, followed by roots packaged with PVC, and plastic bags (Figs.2a and 2b).The lowest fresh weight losses were consistently observed among roots stored in a cold chamber and packaged in plastic bags, leaving the roots with a good appearance and without signs of wilting after up to 30 days of storage.
Fresh weight losses were higher under uncontrolled environmental conditions (47.7%), followed by refrigeration (38.1%) and storaged in the cold chamber (31.35%), with wilting signs seen after 14 days of storaged.Roots stored without any packaging showed high fresh weight (water) losses of up to 84% by the end of the experiment.Water loss by storage organs is directly infl uenced by their surface/volume ratios and by the water pressure defi cit between the plant organ and outside atmosphere (Finger and Vieira 1997).The PVC fi lm ROSILDA M. MUSSURY et al.
reduced the water vapor gradient and consequently diminished root water loss (Ribeiro et al. 2007).
The responses of the roots and tubers of different species to storage at similar temperatures using similar packaging materials were similar to those seen here with P. ahipa (Scalon et al. 2000, 2002, Ribeiro et al. 2007) .Variations in the shelf life of tuberous roots are related to the types of packaging and their storage environment, but the literature consistently confirms that wellpackaged roots can be stored under refrigeration (13 ± 2°C) for long periods of time and still retain commercial quality (Tessarioli Neto et al. 1998, Scalon et al. 2000, 2002, Oliveira et al. 2001, Ribeiro et al. 2007).However, López et al. ( 2010), while evaluating the productivity and the conditions of post harvest management from P. ahipa roots cultivated in Misiones, Argentina, verified that the storage at 25°C was better that under refrigeration.This variation observed by the authors may be attributed to the cultivation conditions.The room temperature used in this research is higher than the temperature one observed for the Misiones region, since it is one of the most humid province of the country and these factors may probably have favoured the root development and consequently, modified the aspects of post harvest conservation.Scalon et al. (2000) observed that beet roots stored at room temperature without any packaging and under temperatures varying from 15 to 26°C became unfi t for commercialization after 14 days due to wilting and fresh weight losses (55%) beets packaged in PVC fi lm, retained good appearances for 22 days under storage, with average weight losses of only 15.82% (six to nine times lower than the unpackaged roots); the largest roots showed smaller losses.Tessarioli Neto et al. (1998) likewise noted that beet roots wilted and sprouted after 12 days of storage in polyethylene packages, while roots packaged in PVC and perforated polyethylene showed no sprouting and their fresh weight losses varied from 2.72 to 4.51%.Scalon et al. (2002) noted that Arracacia roots stored for four days at room temperature were no longer fi t for commercialization, while roots stored without any packaging but held under refrigeration lasted 42 days.Packaging and refrigeration together maintained postharvest quality of Arracacia for up to 112 days.
Although both PVC and plastic bag packaging of "jacatupé" roots held in refrigerators and in cold chambers avoided excessive fresh-weight losses, signs of contamination were observed by the 30 th day.It was noted that PVC and plastic bag packaging resulted in a high incidence of root decay caused by fungi of the genus Aspergillus.According to Oliveira et al. (2001) packaging 765 TUBEROUS ROOTS OF Pachyrhizus ahipa (WEDD) PARODI kept carrots fi rm during storage by reducing water losses, but favored fungal growth (Aspergillus losses, but favored fungal growth (Aspergillus losses, but favored fungal growth ( and Fusarium) and sprouting.
After 30 days, the average data of the TTA of "jacatupé" roots remained higher in roots stored in the refrigerator and packed in plastic bags (2%) (Fig. 3a).At room temperature, the lowest average TTA values were observed in roots without any packaging (0.83%) (Fig. 3b), while the lowest TTA values were seen in roots stored in the cold chamber and packaged in PVC (2.1%) (Fig. 3c).
The root pH of "jacatupé" increased during storage with all treatments (Figs.3d, e, f) (initial value 6.08) (Table I), except among roots stored at room temperature and in plastic bags (5.8).However, pH trends ran contrary to TTA data at all storage temperatures.The soluble solid contents of the roots stored in the refrigerator (Fig. 3g) was similar to the initial value (6.9) (Table I), although roots stored at room temperature and without any packaging (Fig. 3h), as well as those stored in the cold chamber, had the lowest TSS values (Fig. 3i).The literature reports variable root and tuber responses to different storage conditions.Storing carrots at low temperatures stimulates increases in hexose and reductions in sucrose concentrations (Suojala 2000); potatoes stored at temperatures lower than 10°C are susceptible to sweetening through increased starch degradation and sucrose accumulation, and principally through increases in glucose and fructose levels (Blenkinsop et al. 2003, Kumar et al. 2004).

Figure 1 -
Figure 1 -Jacatupé roots, stored at room temperature (a), in cold chamber (b) and in a refrigerator (c) for 30 days, non-packed, packed with PVC and plastic bag.

Figure 2 -
Figure 2 -Mass loss of P. ahipa stored in different environments (a).Mass loss on polystyrene trays without package (WP), on trays packed with commercial plastic bag (PW) and with sealed PVC (b).

Figure 3 -
Figure 3 -Total titratable acidity (TTA), pH, total soluble solids of P. ahipa stored for 30 days on polystyrene trays without package (WP), in commercial plastic bag and on trays packed with sealed PVC, in fridge (A, D, G), at room temperature (B, E, H) and cold chamber (C, F, I).UFGD, Dourados-MS.

Figure 4 -
Figure 4 -Mean value of carbohydrates, proteins, lipids and ashes from P. ahipa stored for 30 days polystyrene trays without package (WP), in commercial plastic bag and on trays packed with sealed PVC, in fridge (A, D, G, J), at room temperature (B, E, H, K) and cold chamber (C, F, I, L).UFGD, Dourados-MS.