Determination of convenient some avocado (Persea american Mill.) cultivars for puree production and the effect of storage temperatures on the product stability

Avocado plantation has steadily been increased in Turkey and it is only consumed as fresh. Avocado is a fruit that could not be stored for a long time cause of its fruit property. Therefore, the fruit is mainly processed for oil production, and into different products in countries in which the production is fairly high. Avocado is also processed as puree in a few countries. Some problems are present faced with puree production and its storage. One of the major problems is enzymatic browning which should intensively be dearth with, and is important for food processing leads to economically important loses. In the present study, avocado puree production possibility was investigated on avocado cultivars (Bacon, Fuerte, Hass, Zutano) having a great potential in Turkey, in three different harvesting period. Some physical and chemical properties of the fruit samples were analysed to characterize raw materials. Each sample was subjected to parameter evaluatitons including fruit weight, seed weight, fruit weight/seed weight and CIE Lab color values for physical; and dry matter, protein, oil, ash content, pH, acidity, total phenolic compound content, free fatty acidity, p-anisidin value, polyphenoloxidase, peroxidase, lipoxygenase activities for chemical properties.Dry matter, protein, oil, ash content, titration acidity and pH value of avocado fruit showed changes between 21.64-37.87%, 1.37-2.15%, 1 1.21-28.59%, 0.87-1.64%, 0.08-0.1 1% and 6.70-7.48, respectively. The mineral content of the fruit was 4.34-6.17 g/kg for potassium, 169.25-262.48 mg/kg for magnesium, 63.23-97.15 mg/kg for calcium, 18.86-38.72 mg/kg for sodium, 1.82-5.17 mg/kg for iron, 2.14-3.69 mg/kg for copper, 3.14-5.18 mg/kg for zinc and 0.88-1.43 mg/kg for manganese. Fatty acid composition analyze of avocado oil was performed with gas chromatography. Palmitic, palmitoleic, stearic, oleic, linoleic, linolenic and arachidic acid composition of the oil changed between 14.01-20.48%, 5.33-9.59%, 0.40-0.72%, 57.71-70.67, 8.28-14.48%, 0.28-0.77% and 0.09-0.18%, respectively. The total phenolic content was determined with UV-spectroscopy. The phenolic compounds were determined with RP-HPLC in three harvesting period of four different avocado cultivars. The total phenolic content of the samples was between 1.04-1.34 mg/g on edible portion (wet weight). In the present study, nine phenolic acids (gallic, protocatechuic, a-resorcyclic, y-resorcyclic, caffeic, ferulic, p-coumaric, p-coumaric, o-coumaric, caffeic, ferulic and sinapic) and three flavonoids ((-) epicatechin, rutin and quercetin) were identified and quantified. The main phenolics determined in fresh edible portions of avocado fruits were (-) epicatechin and rutin as flavonoid and caffeic and protocatechuic acid as phenolic acid. (-)-Epicatechin was the most abundant phenolic compound, which is present in all cultivars. One of the distinguishing features of the avocado fruit is the high oil content. Therefore, the free fatty acidity and p-anisidine value (oxidation degree) of the samples were analysed. The free fatty acidity of the avocado showed changes between 0.31-0.34% (oleic), p-anisidine could not be determined in the samples by the spectrophotometric method used in this study. CIE Lab color values of the samples were measured with Minolta CR-400 chromameter. The L, a, b color values of the fruit samples changed between 62.11- 68.49, (-)9.77-(-)13.71 and 32.42-36.97, respectively. Polyphenoloxidase, peroxidase and VIlipoxygenase activities showed changes between 5.14-9.53, 10.15-23.19, 0.48-0.66 AAbsorbance/minute/ml in avocado cultivars, respectively. These fruits were ripened under controlled-atmosphere condition (25°C, 65% relative humidity), then were cleaned, peeled and cored. Then the mesocarp part of the fruit was homogenized with citric acid, ascorbic acid, sorbic acid and sodyum chloride. The purees were stored up to 6 months under refrigerator (4°C) and deep freezer (-18°C) conditions. Free fatty acidity, p-anisidine value, CIE coordinates (L, a, b), polyphenoloxidase, peroxidase and lipoxygenase activities of the samples were analaysed in each every month within interval up to six months in order to determine stability of the purees. The free fatty acidity, p-anisidine value, CIE coordinates (L, a, b), polyphenoloxidase, peroxidase and lipoxygenase activity values significantly affected by cultivars, harvesting time storage time and temperature. Analyzed some properties showed changes according to storage temparature and period besides harvesting time, variety. Thus, free fatty acidity showed an increase during storage. This increase was considerable level in samples stored at +4°C. The fatty acidity value %0.57 as middle value at the begining of storage reached up to %1.49. p-anisidin has also showed same trend in increase of its content. Measured enzyme activities showed a decrease in storage duration. Polyphenoloxidase, peroxidase lipoxygenase activites of samples, which were 6.71, 10.61 ve 0.45 AAbsorbance/minute/ml at the begining, decreased up to 2.35, 5.52 ve 0.29 AAbsorbance/minute/ml values, respectively. And L, a, b color values of the puree samples changed between 50.36-67.85, -10.91-(-)2.04 and 26.88-36.56, respectively. The result showed that Zutano and Hass were more convenient than Bacon and Fuerte in terms of puree production according to CIE coordinates (L, a, b). First harvest time was found to be suggestable and was comparable with other harvest times. The colour values of purees (CIE Lab) were fairly well preserved at deep frezer (-18°C) up to 6 months, compared to at refrigerator temperature (4°C). The color values of the samples, however, showed a Vllpossibility for puree storing at 4°C up to 6 months, p-anisidine values of the samples were found low, which was under acceptable limit value. Six months at -18°C and 3 months at 4°C were convenient for shelf life of avocado purees according to free fatty acidity. KEYWORDS: Avocado, puree, enzyme activity, color values, oxidation, free fatty acidity