Partial purification and enzymatic characterization of avocado (Persea americana Mill,cv. Hass) lipoxygenase

Detrimental effects on minimally processed fruits and vegetables induced by increased lipoxygenase (LOX) activity are a major concern in the food industry. Partial purification and enzymatic characterization of lipoxygenase (LOX) from avocado fruit (Persea americana Mill, cv. Hass) is presented. Avocado LOX was partially purified by fractional precipitation with ammonium sulfate, followed by anion exchange adsorption. Substrate specificity and effects of temperature, pH and calcium ion concentration on LOX activity were determined. Likewise, the in vitro ability of avocado LOX to co-oxidize β-carotene was determined. LOX showed a higher substrate affinity for linolenic than for linoleic acid. Optimum activity was reached at 40 °C, pH 6.5, and 0.20 mM of calcium ion concentration. Avocado LOX showed β-carotene co-oxidation capability. Considering the optimums and operational ranges established for each studied factor, strategies concerning the inactivation of LOX may be proposed to reduce the detrimental effects on minimally processed avocado products. Additionally, the co-oxidation capability of avocado LOX may be of interest for the avocado industry due to its potential application as a bleaching agent.     

Avocado (Persea americana Mill.) by-products and their impact: from bioactive compounds to biomass energy and sorbent material for removing contaminants. A review

Avocado industry produces enormous by-products and represents an important source of raw material in food and non-food applications. This review aims to focus the attention on the valorisation of avocado wastes recycling to produce different materials with important industrial and environmental impacts. In fact, peels and seeds can be reused in food and cosmetic fields due to the presence of bioactive ingredients such as polyphenols; thanks to their antioxidant and antinflammatory activities. In addition, both peels and seeds can be reused in the production of carbonaceous materials with important consequences for environmental pollution in the removal of contaminants from water. Interesting applications of avocado wastes in photocatalysis and biofuel production are also discussed. All the utilisations attest the great potential of recycling avocado by-products, a little known resource.     

Physicochemical characterisation and in vitro Starch digestion of Avocado Seed Flour (Persea americana V. Hass) and its starch and fibrous fractions

The avocado seed is considered a by-product of their pulp exploitation and today it does not present relevant food or industrial applications. In this study, we evaluate the potential use of its flour, their isolated starch and fibre fractions. After processing, the flour yielded 46.28%, and showed 6.7% of protein and low fat and ash contents (3.4, and 2.71% respectively). The starch yielded 27.28% with low-fibre content that influenced its viscosity properties; as well as their water absorption index (WAI), water solubility index (WSI) and oil absorption index (OAI), that were 2.43%, 11.22% and 0.16% respectively. The in vitro starch digestion of the different obtained fractions showed higher amounts of rapidly digestible starch (56.8%–75.36%, flour and starch respectively). The functional properties of the materials were correlated with strong molecular interactions with their apparently unique amylose structure; for this, this by-product may have different potential for food applications.     

Physical, chemical and palynological characterization of avocado (Persea americana Mill.) honey in Israel

Various methods were used to characterize avocado honey in Israel. Perseitol, a unique sugar present only in avocado honey, served as an indicator for the degree of purity of avocado honey. Low avocado pollen counts made the common melissopalynology method ineffective at predicting the contribution of avocado nectar to honey. It was also found that the levels of fructose, sucrose and glucose do not uniquely characterize avocado honey. Potassium content and eight other minerals were linearly highly correlated to perseitol content. Moreover, pH level, absorbance and degree of darkness were significantly correlated to perseitol content, and can therefore be used to characterize avocado honey.     

Characterisation of avocado (Persea americana Mill) honeys by their physicochemical characteristics

The quality of 12 avocado (Persea americana Mill) honeys from Spain was evaluated. Eight common physicochemical parameters were analysed, namely water content, pH, acidity (free, lactonic and total), sugar content, ash content and electrical conductivity. In addition, the honey samples were analysed using inductively coupled plasma optical emission spectrometry (ICP‐OES), and six minerals were quantified for each honey, namely potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), phosphorus (P) and sulphur (S). Most samples showed proper maturity considering the medium water content (mean 17.7%). The total acidity (below 50 meq kg^?1 except for one sample) indicated absence of undesirable fermentation; also, the mean pH of around 4.77 is usual in this kind of honey. The values for ash content and electrical conductivity were high (0.77% and 798 µS cm^?1 respectively) and typical of dark honeys. K was the predominant mineral (accounting for 73% of the total minerals quantified), followed by Na (10%). Copyright © 2004 Society of Chemical Industry     

Bioactive compounds and antioxidant activity from harvest to edible ripeness of avocado cv. Hass (Persea americana) throughout the harvest seasons

The influence of regular air cold storage (7 °C and 85 ± 5% RH) followed by ripening at shelf-life conditions (19–21 °C and 65 ± 5% RH), on bioactive compounds of Hass avocados was investigated. Results showed that the content of mannoheptulose and perseitol decreased significantly already during cold storage and ripening period. The fatty acid profile and contents of tocopherols (α- and β-tocopherol) and phytosterols (β-sitosterol, stigmasterol, campesterol) remained unchanged from day 0 to edible ripeness. Total phenolics, hydrophilic and lipophilic antioxidant capacity remained unchanged during cold storage and increased during the ripening period. At edible ripeness, significant amounts of phenolic acids, p-coumaric and caffeic and their derivatives were synthesised. Our results demonstrated that regular air cold storage for up to 37 days followed by ripening at shelf-life conditions enhances the phenolic compounds and mainly the hydrophilic antioxidant capacity without affecting the remaining bioactive compounds in Hass avocado.     

1-MCP结合壳聚糖涂膜延迟油梨果实后熟的研究

研究了壳聚糖、1-甲基环丙烯(1-MCP)及其复合处理对采后"哈斯"油梨果实后熟的影响.油梨果实先用1-MCP处理24 h,再用2.0% CTS水溶液处理,然后贮存在20℃、85%～90%相对湿度下后熟,在此期间取样分析乙烯释放量、硬度、失重、色度指数、多聚半糖醛酸酶(PG)和多酚氧化酶(PPO)的活性.结果表明:与对照相比,以100nL/L的1-MCP处理24 h和20 g/L的壳聚糖涂膜处理可以明显降低果实的乙烯、CO2释放量,并延迟果实呼吸高峰的出现,减少质量损失,推迟硬度下降,延缓果皮颜色的变化,同时抑制PG和PPO的活性.1-MCP处理结合壳聚糖涂膜延迟油梨果实后熟的效果更明显,果实的后熟时间约延迟12 d.以上结果说明两者结合处理能有效地延迟油梨果实的后熟.     

Laboratory preparation and evaluation of Pollock variety avocado (Persea americana Mill) guacamole

Guacamole was produced from ripe avocado (Persea americana) by blending the pulp with local herbs, spices and salt. The guacamole was stored at 5 °C for 2 weeks, during which physical, chemical and microbial analyses were conducted. Organoleptic evaluations by a semi‐trained panel were also performed, until the guacamole was deemed unfit for human consumption. The results indicated that fresh avocado pulp contains 835, 13, 16, 92, 44, 16 and 0.078 g kg^?1, moisture, ash, protein, fat, carbohydrate, fiber, and vitamin C respectively, and has a pH of 6.7; compared with 838, 13, 16, 92, 44, 16, and 0.042 g kg^?1, respectively, of the same nutrients in freshly prepared guacamole, which has a pH of 6.0. During storage, the moisture content, consistency, total soluble solids and total titratable acidity (as citric acid) of the guacamole increased, but the vitamin C content decreased. The color of the avocado pulp, which darkened during conversion into guacamole, darkened further as storage increased as evidenced by a decrease in the L, a and b values. Sensory evaluation revealed that the mean storage period (5 °C) for the guacamole was 6 days. Although the fresh avocado pulp, the freshly prepared guacamole, and the stored guacamole contained bacteria, yeasts and molds, the pathogens Staphylococcus aureus and Salmonella were absent. Copyright © 2007 Society of Chemical Industry     

Characterization and application of a coating of starch extracted from avocado (Persea americana L. cv. Hass) seeds as an alternative to reduce acrylamide content in French fries

Food Science and Biotechnology - The starch extracted from avocado (Persea americana L. cv. Hass) seeds was characterized and used in the preparation of an edible coating to reduce the oil uptake...     

Effect of pepper tree (Schinus molle) essential oil-loaded chitosan bio-nanocomposites on postharvest control of Colletotrichum gloeosporioides and quality evaluations in avocado (Persea americana) cv. Hass

Food Science and Biotechnology - Preventive and curative activity of postharvest treatments with chitosan nanoparticles (CS) and chitosan biocomposites loaded with pepper tree essential oil...     

Volatile components of avocado leaves (Persea americana mill) from the Mexican race

The chemical composition of the volatile oil of avocado leaves from Mexican race (Persea americana Mill) grown in the highlands of Mexico was investigated by gas chromatography and gas chromatography-mass spectrometry. Thirty compounds were identified accounting for 92.45% of the oil. Estragol (78.12%), α-cubebene (3.58%), methyl eugenol (3.37%) and β-caryophyllene (2.10%) were the major components representing more than 87%. The oil has a characteristic aroma similar to anise-tobacco.     

Reduction of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes with electrolyzed oxidizing water on inoculated hass avocados (Persea americana var. Hass)

This study was intended to evaluate the bactericidal effect of electrolyzed oxidizing water (EOW) and chlorinated water on populations of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes inoculated on avocados (Persea americana var. Hass). In the first experiment, inoculated avocados were treated with a water wash applied by spraying tap water containing 1 mg/liter free chlorine for 15 s (WW); WW treatment and then spraying sodium hypochlorite in water containing 75 mg/liter free chlorine for 15 s (Cl75); WW treatment and then spraying alkaline EOW for 30 s (AkEW) and then spraying acid EOW (AcEW) for 15 s; and spraying AkEW and then AcEW. In another experiment, the inoculated avocados were treated by spraying AkEW and then AcEW for 15, 30, 60, or 90 s. All three pathogen populations were lowered between 3.6 and 3.8 log cycles after WW treatment. The application of Cl75 did not produce any further reduction in counts, whereas AkEW and then AcEW treatment resulted in significantly lower bacterial counts for L. monocytogenes and E. coli O157:H7 but not for Salmonella. Treatments with AkEW and then AcEW produced a significant decrease in L. monocytogenes, Salmonella, and E. coli O157:H7 populations, with estimated log reductions of 3.9 to 5.2, 5.1 to 5.9, and 4.2 to 4.9 log CFU/cm2, respectively. Spraying AcEW for more than 15 s did not produce any further decrease in counts of Salmonella or E. coli O157:H7, whereas L. monocytogenes counts were significantly lower after spraying AcEW for 60 s. Applying AkEW and then AcEW for 15 or 30 s seems to be an effective alternative to reduce bacterial pathogens on avocado surfaces.     

Evolution of Mineral Contents in Tomato Fruits During the Ripening Process After Harvest

A comparative study was carried out to evaluate the mineral content of tomato during ripening after harvest. Calcium (Ca), magnesium (Mg), sodium (Na), phosphorus (P), potassium (K), selenium (Se), and zinc (Zn) contents were determined in three of the main tomato types (round, elongated, and cherry) consumed in Portugal. Ca, Mg, Se, and Zn were determined by atomic absorption spectrometry, Na and K by flame photometry, and P by visible spectrometry. No significant variation was found in the Zn, P, Na, and K concentrations during the tomato ripening after harvest. For Ca, Mg and, especially, Se, significant variations in their corresponding concentrations were observed. The content of Ca and Mg tended to decrease from the initial concentration. Conversely, a considerable increase in Se content was observed. A decrease in total tomato mineral content was determined for all studied types after an 11-day period of maturation after harvest. Therefore, a new and significant aspect to emphasize as an outcome of this study is that an 11-day post-harvest ripening period for tomato ingestion by the final consumer should be recommended in order to benefit from the highest mineral content. This acquaintance could be very important for tomato agricultural practices and for economic development of this type of cultivation, as well as for the consumer’s health.     

复合菌种对发酵鲢鱼成熟过程中品质的影响

为了研究接种复合菌对发酵鲢鱼成熟过程中品质的影响,作者对发酵鲢鱼成熟过程中的菌落数、pH和总酸、生物胺、总氮(TN)、游离氨基酸(FAA)、硫代巴比妥酸(TBA)、游离脂肪酸(FFA)和挥发性风味成分进行测定,结果表明,混合菌种组的微生物增长显著高于对照组,发酵成熟后,接种组中的总酸、TN、TBA、EPA(二十碳五烯酸)和DHA(二十二碳六烯酸)质量分数显著高于对照组;pH、生物胺质量分数低于对照组;FAA质量分数在成熟第6 d达到最高,接种组达到0.030 5 mg/g,明显高于对照组;接种组中的质量分数明显高于对照组。此外,GC-MS的结果显示接种组的挥发性风味成分中醛类、酮类和酯类化合物的质量分数有不同程度的增加。可见,复合菌种对发酵鲢鱼成熟过程中的蛋白质和脂肪的变化起到至关重要的作用,增强了其安全性,并促进了发酵鲢鱼风味的形成。     

Color Changes of Tamarind (Tamarindus indica L.) Pulp During Fruit Development,Ripening, and Storage

Tamarind (Tamarindus indica L.) is a member of the dicotyledonous family Leguminosae. The fruit pulp has a pleasant acid taste and rich aroma, and thus, it is used as the chief souring agent for curries, sauces, and certain beverages. The unripe fruit pulp is green in color, while the ripe pulp is light brownish red. In storage, the brown pulp turns slowly to deep brown and finally black in color. In the present study, the cause of color changes during developmental stage, as well as during storage of tamarind pulp was investigated. Tamarind pulp in unripe condition (green pod) shows polyphenol oxidase activity up to 105 days of maturity of the fruit or until it ripens. Thereafter due to ripening there is a marked increase of reducing sugars and available lysine leading to Maillard reaction. This inhibits enzymatic browning in the ripe pulp during subsequent storage.     

汤料对青方腐乳后期发酵过程中主要成分、质构及臭味的影响

本文研究了某市售青方乳腐汤料对青方腐乳主要成分、质构及臭味的影响。结果表明,在后期发酵过程中,与空白腐乳（未添加该汤料的腐乳）相比,样品腐乳（添加该汤料的腐乳）的蛋白质和粗脂肪的含量较低,而游离氨基酸含量较高,后酵49d时,样品腐乳的游离氨基酸含量达到11.7%（干重）,比空白腐乳氨基酸含量提高了60%左右;质构参数方面,样品腐乳的硬度和弹性较低,而粘聚性较高,后酵第49 d时,样品腐乳坯体的硬度、粘聚性和弹性分别为213.75 g、0.37和0.35,空白腐乳坯体的硬度、粘聚性和弹性分别为258.28 g、0.29和0.43;两种腐乳坯体质构参数（硬度、粘聚性和弹性）与坯体蛋白质含量存在着显著的相关性。接种此汤料可使腐乳产生挥发性硫化物和吲哚,但此汤料经过较高转速离心及微孔滤膜过滤后不能使腐乳产生这些物质。