INHIBITORY EFFECT OF VEGETABLE EXTRACTS ON BROWNING OF REFRIGERATED AVOCADO

BUSTOS, MARIELA C.; MAZZOBRE MARÍA FLORENCIA; BUERA, MA. PILAR

Rosario

Congreso; 5º Simposio Internacional de Nuevas Tecnologías. III Simposio Latinoamericano sobre Higiene y Calidad de Alimentos. Congreso Argentino de Ciencia y Tecnología de Alimentos; 2013

Enzymatic browning reactions limit the acceptability of avocado; therefore color preservation during storage becomes one of the main objectives for fruit processors. The aim of this work was to evaluate the anti-browning potential of Allium and Brassica extracts on avocado sliced and purée during refrigerated storage, and its relation with the sample structure. Fully mature Allium (garlic, scallion and onion) and Brassica (white cabbage, cauliflower and brussels sprouts) vegetables were washed, cut into pieces, homogenized and extracted under constant agitation in phosphate buffer solution pH 6.0 at 50 °C. After centrifugation, extract solution was freeze dried. Avocado was cut into slices or smashed to obtain the puree samples. Avocado slices were immersed in vegetables extracts solutions (10% p/v in phosphate buffer pH 6.0) for 15 minutes and drained. Puree samples were mixed with the extracts (5 g/100 g of puree at pH 4.0). Avocado slices dipped in phosphate buffer and puree without extract addition were analyzed as control. All samples were stored at 4 °C in hermetically sealed glass plates. Changes in color of the slices and puree were determined by image analysis and then converted to the CIELAB coordinates (L*, a* and b*). The limit storage time considering color acceptability was calculated as the time for completely lost of green component (a*>0). In puree samples, polyphenol oxidase activity was measured spectrophotometrically. Present results showed that avocado became darker (L* decrease), and less yellowness (b* decrease) and greenness (a* increase) during refrigerated storage. L* values were lower in avocado slices than in puree samples during the analyzed period (96 h for slices and 30 days for purée) indicating that browning was more evident on slices than in puree. Scallion extract had the best antibrowning properties: ΔL* value after 4 days of storage was -4.3 for slices and no significative changes were observed in purée. In addition, color acceptability (according to a*) was conserved in both samples. White cabbage was the most effective crucifer extract while brussels sprouts slightly increase browning. Color appearance of purée treated with cabbage extract was acceptable after 30 days of storage and until 96 h for avocado slices. Garlic, onion and cauliflower extracts presented an intermediate behavior compared to scallion and brussels sprouts. In puree samples treated with scallion extract, it was also observed that inhibition of browning correlated with a lower polyphenol oxidase activity. Allium extracts (except for onion) were more effective for delaying browning, both in avocado slices and purée compared to Brassica vegetables. Present results showed that browning kinetics depended strongly on the structure of the sample (avocado slices darkened more than purée) and also on the type of extract. This work opens a real possibility of using Allium species for developing natural food ingredients with functional properties and provides a useful basis for employment as antibrowning in other matrices.