Journal of Agricultural Engineering 2015; volume XLVI:467 Avocado oil extraction processes: method for cold-pressed high-quality edible oil production versus traditional production Giacomo Costagli, Matteo Betti Alfa Laval SpA - Market Unit Food, Beverage & Olive Oil, Tavarnelle Val di Pesa (FI), Italy Abstract Introduction Nowadays the avocado fruit (Persea americana Mill.) is widely The avocado fruit originated in Southern Mexico where archaeolog- regarded as an important fruit for its nutritional values, as it is rich in ical remains and other evidence indicate that its cultivation started in vital human nutrients. The avocado fruit is mainly sold fresh on the very ancient times, possibly some 6000 years ago. Avocados were market, which however trades also a relevant quantity of second-grade grown at the time of the Conquest and spread from Northern Mexico fruits with a relatively high oil content. Traditionally, this oil is extract- southwards across Central America into North-Western Latin America, extending southwards in the Andean region down to Peru and east- ed from dried fruits by means of organic solvents, but a mechanical wards into the Andean region of Venezuela (Popenoe, 1935). The com- method is also used in general in locations where drying systems mercial exploitation of avocado began in the early 1900’s by and/or solvent extraction units cannot be installed. These traditional Californians. Its production in the tropical areas of the world has processes yield a grade of oil that needs subsequent refining and is grown steadily over the last decade and currently accounts for about mainly used in the cosmetic industry. In the late 1990s, in New Zeland, three million and eight hundred thousand tons of fresh fruit. Most of a processing company with the collaboration of Alfa Laval began pro- the produce is grown for fresh consumption, which is also on the ducing cold-pressed avocado oil (CPAO) to be sold as edible oil for sal- increase (FAO, 2014). ads and cooking. Over the last fifteen years, CPAO production has The avocado fruit (Persea americana Mill.) is widely regarded today increased in many other countries and has led to an expansion of the as an important fruit for its nutritional values, as it is rich in vital market which is set to continue, given the growing interest in high- nutrients for the human body. There has recently been an increasing quality and healthy food. Avocado oil like olive oil is extracted from the demand in antioxidants, given their beneficial effects on human fruit pulp and in particular shares many principles of the extraction health. In this respect, avocados contain three of the most important process with extra-vergin olive oil. We conducted a review of tradition- ones, which are vitamins. Avocado fat consists predominantly of mono- al and modern extraction methods with particular focus on extraction unsaturated oleic acid, which has been found to reduce harmful low- processes and technology for CPAO production. density lipoprotein cholesterol, while maintaining beneficial high- density lipoprotein cholesterol, and to perform better than typical low- fat diets (Bergh, 1992; Fulgoni et al., 2013). Although avocado is pri- marily consumed fresh, a substantial increase in the use of avocado- based products (e.g., guacamole) and oil for cosmetics and culinary Correspondence: Giacomo Costagli, Alfa Laval SpA - Market Unit Food, purposes also suggest further market growth (Bost et al., 2013). Beverage & Olive Oil, via Sangallo 33, 50028 Tavarnelle Val di Pesa (FI), Italy. Tel.: +39.03927041390. E-mail: [email protected] Avocado fruit and oil extraction Key words: Avocado; oil; cold-pressed; centrifuge; extra virgin; Alfa Laval. The avocado plants include three different horticultural varieties Contributions: the authors contributed equally. named after their presumed areas of origin: Guatemala, Mexico and West Indies. Each variety is marked by many different traits, some of Conflict of interest: GC and MB, who contributed part of the materials used which are of commercial relevance (Bergh and Ellstrand, 1986). Today, in this study, are employees of Alfa Laval SpA (Tavarnelle Val di Pesa, from the agronomical point of view, there are many varieties with a Florence, Italy). wide range of sizes, forms and compositions of the fruit. For instance, For instance, Table 1 reports the characteristics of different fruits from Received for publication: 21 April 2015. varieties harvested in Venezuela (Gómez López, 2002) and clearly Accepted for publication: 20 August 2015. shows an example of their variability in particular in terms of size, oil content and seed/pulp proportions. In general, the fruit is roughly pear- ©Copyright G. Costagli and M. Betti, 2015 Licensee PAGEPress, Italy shaped and more or less elongated. Its weight may range from 60 g to Journal of Agricultural Engineering 2015; XLVI:467 700 g. The relative amount of pulp varies from 60 to 75% according to doi:10.4081/jae.2015.467 the cultivar. The oil content may also vary widely. The kernel contains only about 1% of oil, whereas the skin accounts for less than 4% This article is distributed under the terms of the Creative Commons (Jacobsberg, 1988). Figure 1 shows the average composition of a Hass Attribution Noncommercial License (by-nc 3.0) which permits any noncom- avocado from New Zealand. Requejo-Tapia (1999) in New Zealand mercial use, distribution, and reproduction in any medium, provided the orig- described the Hass variety as being the most compatible with high- inal author(s) and source are credited. quality oil extraction due to its large amount of flesh with a high oil [Journal of Agricultural Engineering 2015; XLVI:467] [page 115] Review content. Depending on the location of the orchard, the oil content of extracted/oil content). The resulting oil is brownish with a high pig- these fruit flesh can range from 16-17% in September to 25-30% in ment content and needs to be refined for most applications. Refining April depending on the fruit ripening stage (Requejo-Tapia, 1999). consists of three steps: deacidification to remove free fatty acids which The market of fresh avocado is certainly the main one and also gener- are less than 1% in good-quality fruits; bleaching to remove chloro- ates a remarkable quantity of second-grade produce which is discarded, phylls and their degradation products, pheophytins, as well as despite its relatively high oil content. The avocado oil can be extracted in carotenoids; de-odourisation. When oil is sold crude, it is generally win- different ways. It is contained in a finely-dispersed emulsion in the cells terised at 5°C and drummed in lacquer-lined drums (Human, 1987; of the fruit pulp. Hence, the extraction process requires rupturing not Martinez Nieto et al., 1988). only the cell walls, but also the structure of the emulsion (Lewis et al., 1978). Traditionally, this oil used to be obtained by mashing the pulp in water, then heating and skimming off the supernatant oil. Later, for cost reasons, most producers started to extract oil from dried fruits by means Traditional mechanical extraction of solvents (Sadir, 1972; Human, 1987; Martinez Nieto et al., 1988). Two main methods are in use to extract avocado oil for industrial production. The mechanical method has been used traditionally in locations According to the first method, fruits are dried and pressed at high tem- where drying facilities and/or solvent extraction units cannot be perature, subsequently oil is extracted by means of organic solvents. In insalled. However these processes have poor yields and frequently the second method, oil is separated from fruits by centrifugal or pressing require the use of chemical aids. forces, then oil cells are submitted to mechanical and enzymatic distruc- Avocado oil extraction was generally obtained by peeling and de- tion (Human, 1987; Werman and Neeman, 1987; Martinez Nieto et al., stoning the fruit, mashing the pulp and eventually drying it, then heat- 1988; Bizmana et al., 1993). The second method was developed in order ing the paste with hot water with chalk and/or NaCl, and spinning, to cut energy costs and minimise the air pollution caused by organic sol- vents. Nevertheless, in both cases, the crude avocado oil still needs to be refined before final consumption and use in the cosmetic industry, where it is particularly appreciated for its high vitamin E content and emollient properties, although it is considered marginal as a food prod- uct (Eyres et al., 2001). The first attempt to develop a method to produce cold-pressed oil intended to obtain high-quality edible oil was made back in the late 1990’s by a New Zealand company in collaboration with Alfa Laval (Eyres et al., 2001). In the follow paragraph we compare shortly the three main extraction methods: chemical extraction by solvent, tradition- al mechanical extraction and the most recent cold-pressed mechanial method for high-quality edible oil. In the description of the last one, we will focus in particular on Alfa Laval extraction plant, process parameters and oil quality. However this paper does not mention other variations of the main methods used in the past for avocado oil extraction (Human, 1987). Chemical extraction by solvents Organic solvent extraction is the most widespread. Warm air drying of the pulp followed by hexane solvent extraction yields 95% oil (oil Figure 1. Average composition of a Hass avocado in New Zealand. Table 1. Fruit characteristics of different varieties of avocado harvested