Fabiana Fumi Sasaki

Quality of minimally processed beet roots stored in different temperatures

ABSTRACT The present work was carried out with the objective to determine the effect of different storage temperature on thequality of beet root minimally processed. Respiratory activity and mass loss were higher in the storage at 15 o C. Nosignificant differences in color, total soluble solids, betacyanin and betaxanthin were observed among treatments.Based on the results obtained, the storage at 0 o C was recommended to storage beet root minimally processed andthat 10 and 15 o C drastically reduced the quality of minimally processed beet roots during storage.Key words: Beta vulgaris L., fresh-cut, betalains, respiratory rate * Auth or for c respondence INTRODUCTION Beet is a root vegetable of the Chenopodiaceaefamily whose edible part is its tuberous root. Itspurple-red color is due to the presence of betalainpigments. These pigments are similar toanthocyanins and flavonoids, which were wronglytermed in the old literature as anthocyaninscontaining nitrogen. Betalains are water-solublepigments and are found only in ten families of theCentrospermae group and are divided into twoclasses: red betacyanin and yellow betaxanthin,which provide beet roots with their typical color(Fenena, 1995). Besides, these pigments oftenexhibit antioxidant activity and potential healthbenefits of vegetables (Kanner et al., 2001).Minimal processing (fresh-cut) comprisesselection, washing, peeling and cutting proceduresthat are aimed at producing a product that is freshand convenient to prepare and consume (Burns,1995). Minimally processed fruits and vegetablesare more perishable than their whole counterparts,due to undergoing severe physical stressesespecially during peeling and cutting procedures.Cutting, associated with high storage temperatures,leads to an increase in the respiratory rate, with anincrease in the activity of enzymes involved inspecific reactions (Chitarra, 1998).Temperature control is the most common andimportant technology to minimize the effects ofcutting in fruits and vegetables (Brecht, 1995).Whole and sliced carrots kept at 0 and 10

Effect of antioxidants in fresh cut radishes during the cold storage

The objective of this study was to evaluate the eff iciency of antioxidants in the cold storage of fres h cut radishes. The shredded roots were submerged in the respective treatments during 3 min (ascorbic acid or citric a cid) and stored at 5oC and 90% RH during 10 days. The radish treated with ascorbic acid showed the higher respi ratory rate in the first 4 h after the processing during the storage. The content of total soluble solids (TSS) wa s significantly higher in the treatment with citric acid. There was an increase in the content of ascorbic acid after two day of storage in the treatments with this antioxidant. Th e values of lightness (L*) were decreasing along th e storage. Citric acid treatments caused strongly red colorati on in the minimally processed roots. None of the tr eatments avoided the browning of the shredded radishes durin g the cold storage.

Phytotoxicity associated to microcystins: a review

Microcystins (MC) are the most studied toxins of cyanobacteria since they are widely distributed and account for several cases of human and animal poisoning, being potent inhibitors of the serine/threonine protein phosphatases 1 (PP1) and 2A (PP2A). The phosphatases PP1 and PP2A are also present in plants, which may also suffer adverse effects due to the inhibition of these enzymes. In aquatic plants, biomass reduction is usually observed after absorption of cyanotoxins, which can bioaccumulate in its tissues. In terrestrial plants, the effects caused by microcystins vary from inhibition to stimulation as the individuals develop from seedling to adult, and include reduction of protein phosphatases 1 and 2A, oxidative stress, decreased photosynthetic activity and even cell apoptosis, as well as bioaccumulation in plant tissues. Thus, the irrigation of crop plants by water contaminated with microcystins is not only an economic problem but becomes a public health issue because of the possibility of food contamination, and this route of exposure requires careful monitoring by the responsible authorities.

Activity of enzymes associated with the enzymatic browning of minimally processed potatoes

The purpose of the present study was to evaluate th e effect of different potato cultivars and storage temperatures on the specific activity of phenylalanine ammonia-lyas e (PAL), polyphenol oxidase (PPO) and peroxidase (P OD) in minimally processed potatoes. Potato cultivars Agat a, Asterix and Monalisa were selected, washed, peel ed, diced, sanitized, centrifuged, vacuum- packed and stored a5 and 15°C for 9 and 5 days, respectively. There was an increase in the enzymatic activity in all the cultivars stored at 15°C. The cultivars ‘Agata’ and ‘Ast erix’ stored at 5oC did not differ significantly between them for tPAL, PPO and POD activities. The PAL, PPO and PO D activities were also influenced by the storage temp erature. The cultivars Agata and Asterix were more suitable in minimal processing than ‘Monalisa’, which was more susceptible to oxidative browning.

Alteração do metabolismo respiratório em rabanetes minimamente processados

The present experiment was aimed at determining the respiratory rate and ethylene production of fresh cut radish and whole radish during cold storage. The rates were evaluated during the first 4 hours after processing and daily, during 10 days at 5°C (± 1°C) and 90% (± 5%) RH. Radishes not processed presented lower respiratory rate (40.61mL CO2 kg-1 h-1) if compared to shredded radishes (93.90mL CO2 kg-1 h-1) 4 hours after processing. Whole and fresh cut radishes showed the highest respiratory rate in the 2nd day of storage with 99.27 and 170.32mL CO2 kg-1 h-1, respectively. On the 10th day of storage, fresh cut radishes showed respiratory rate 149% higher than whole radishes. The minimal processing operations, mainly the cut, enhanced the respiratory rate.

Sensitivity of salad greens (Lactuca sativa L. and Eruca sativa Mill.) exposed to crude extracts of toxic and non-toxic cyanobacteria

We evaluated the effect of crude extracts of the microcystin-producing (MC+) cyanobacteria Microcystis aeruginosa on seed germination and initial development of lettuce and arugula, at concentrations between 0.5 μg.L(-1) and 100 μg.L(-1) of MC-LR equivalent, and compared it to crude extracts of the same species without the toxin (MC-). Crude extracts of the cyanobacteria with MC (+) and without MC (-) caused different effects on seed germination and initial development of the salad green seedlings, lettuce being more sensitive to both extracts when compared to arugula. Crude extracts of M. aeruginosa (MC+) caused more evident effects on seed germination and initial development of both species of salad greens than MC-. Concentrations of 75 μg.L(-1) and 100 μg.L(-1) of MC-LR equivalent induced a greater occurrence of abnormal seedlings in lettuce, due to necrosis of the radicle and shortening of this organ in normal seedlings, as well as the reduction in total chlorophyll content and increase in the activity of the antioxidant enzyme peroxidase (POD). The MC- extract caused no harmful effects to seed germination and initial development of seedlings of arugula. However, in lettuce, it caused elevation of POD enzyme activity, decrease in seed germination at concentrations of 75 μg.L(-1) (MC-75) and 100 μg.L(-1) (MC-100), and shortening of the radicle length, suggesting that other compounds present in the cyanobacteria extracts contributed to this result. Crude extracts of M. aeruginosa (MC-) may contain other compounds, besides the cyanotoxins, capable of causing inhibitory or stimulatory effects on seed germination and initial development of salad green seedlings. Arugula was more sensitive to the crude extracts of M. aeruginosa (MC+) and (MC-) and to other possible compounds produced by the cyanobacteria.

Respiratory activity and pigment metabolism in fresh-cut beet roots treated with citric acid

Beet roots cv. Early Wonder were graded for firmness, color and size, and were peeled inside a cold room (10°C). Roots were then shredded (2 mm thick), sanitized for 6 minutes (NaClO/200 mg L -1 ), rinsed and centrifuged. Fresh-cut beet roots were then treated for 5 minutes with citric acid in the following concentrations: 0 (control), 500; 1,000; 1,500 and 2,000 mg L -1 . The material was centrifuged again, placed in trays, wrapped with PVC plastic film, and stored at 5°C and 85-90% HR for 10 days. Every two days, treatments were analyzed for respiratory activity and betacyanin and betaxanthin contents. The application of citric acid caused the reduction of respiratory rate in the fresh-cut tissue. In the second day of storage, control showed the highest respiratory activity among treatments, reaching around 77 mL CO 2 kg -1 h -1 . Citric acid solution dips in a concentration higher than 500 mg L -1 contributed to a decrease in respiratory activity and no peak in CO 2 evolution was observed. There were significant differences among all treatments during the storage period for the contents of betacyanin, which were around 40; 45; 48; 51 and 55 mg 100 g -1 for the fresh-cut material treated with 0; 500; 1,000; 1,500 and 2,000 mg L -1 of citric acid, respectively. Also, levels of betaxanthin were around 25; 29; 33; 35 and 39 mg 100 g -1 for the material treated with 0; 500; 1,000; 1,500 and 2,000 mg L -1 of citric acid, respectively. The application of citric acid after minimal processing apparently have the ability to reduce respiratory rate and the degradation of pigments, which contributes to extend the shelf life of the fresh-cut product.