General method

2.1.3.1 Almonds

Almond tree, Prunus dulcis (Miller) D.A. Webb, synonym Amygdalus communis L., is a cultivated tree originating from wild trees from Central Asia, which is currently dispersed throughout the world. The almond tree is adapted to dry and hot climates, and that is the reason why it is mainly established in Mediterranean countries (Portugal, Spain, Italy, France) and others with similar climatic characteristics, like USA (specifically California), Australia, South Africa, Chile and Argentina (Monteiro et al., 2003).

The almond is not a true nut, but a drupe, which consists of an outer dehiscent hull (exocarp) and a hard shell (endocarp) with the edible seed (kernel) inside, involved by a brown seed coat (Monteiro et al., 2003). The almond kernel is a very nutritious seed, with extremely low water content (4 to 6%), and high levels of protein (18%), fat (54%) and carbohydrates (20%) (Wareing et al., 2000). Fat content is almost exclusively constituted by unsaturated fatty acids (Sathe et al., 2008; Celik et al., 2010), and the most important sugars are saccharose and raffinose (Barreira et al., 2010). It is also rich in a wide variety of minerals like calcium, potassium, iron and phosphorus (Wareing et al., 2000).

The almond is harvested when it reaches complete dryness, during late August and September, usually by mechanical shaking of the tree or by shaking the fruits with a wood stick. The fruits are collected immediately after fall and dried for a few weeks or months until they reach water content of less than 6% (Monteiro et al., 2003). In this way, almonds are considered the fruits which withstand the longest storage periods without visible depreciation, if adequate environmental conditions (mainly humidity) are maintained (Monteiro et al., 2003). As such, almonds’ major problem in term of biological infestation is insect damage while still on the tree, and significant fungal contamination is usually associated with insect-damaged fruits (Schade et al., 1975; Schatzki & Ong, 2001;

Campbell et al., 2003; Whitaker et al., 2010).

Portugal is the eighteenth country in the list of producing countries, and is responsible for only 0.5% of worldwide production (Figure 2.1). The major producer is, by far, the USA, representing more than 50% of worldwide production, with yields 3 times higher than the world average. The other most important countries, Spain and Italy, are

from the Mediterranean basin, like Portugal. National production has been suffering tremendous reduction of production and yield in the last decade. Throughout a period of 5 years, from 2001 to 2005, and even if the area of production was maintained near 38,000 hectares, the production suffered a two-fold reduction, from 27,000 ton to 13,800 ton, with yields reducing from 891 to 263 kg/ha (INE, 2005). The yield is, in fact, much lower than the world average, and is only one-tenth of the American yield. International trade balance pends for exportation of in-shell fruits for Europe (mainly Spain) and importation of shelled fruits from Spain and California, USA. Portugal imports six times more than it exports (1,600 ton vs. 260 ton; 6 million euros vs. 900,000 euros).

In Portugal, the northeast region of Trás-os-Montes is the major national producer of almonds. Even with low yields, the culture represents significant cultural and economic incomes for local populations, since, under the traditional culturing methods, no major inputs are made other than harvesting. The region integrates one almond Protected Denomination of Origin (Denominação de Origem Protegida, D.O.P), D.O.P. Douro. In 2005, Trás-os-Montes almond represented 60% of the national almond area (approximately 22,800 ha) and 90% of the national production (12,000 tons) (INE, 2005). Yields for Trás-os-Montes production are around 0.5 Ton/ha, which represents 144% of the national yield.

The rest of the national almond is produced in the south region of Algarve, with yields five-fold lower. These numbers reflect mostly the progressive abandonment of the culture in the south of the country.

Figure 2.1 Worldwide almond production (A) and area of production (B) of the 3 major producers and Portugal, for the year 2008 (http://faostat.fao.org, accessed 16.07.2010).

2.1.3.2 Chestnuts

Chestnuts are produced by a wide variety of species from the genus Castanea. These species divide into three major groups that have specific geographical distribution:

C. crenata and C. molissima predominate in Asia and produce the Asian (Japanese and Chinese) chestnuts; C. dentata produces American chestnuts in North America, and C. sativa produces the European chestnuts, also known as sweet chestnuts. C. sativa is adapted to regions with humid and temperate to cold climate, and does not withstand long hot and dry periods (Serrano et al., 2001).

European chestnuts are the most consumed chestnuts because of their interesting nutritional characteristics. They are rich in carbohydrates (around 40%), mostly starch, and present minerals, vitamins and appreciable levels of fiber, but low amounts of protein (2−4%) and, unlike typical nuts, low amounts of fat (1.5−5%) (Wareing et al., 2000;

Barreira et al., 2009). They are also an interesting source of essential fatty acids (Barreira et al., 2009).

Chestnuts have approximately 50% water content (Wareing et al., 2000; Barreira et al., 2009), and for that reason they are typical seasonal fruits that maintain their optimal commercial quality, turgescence and health for only a brief period when compared to other nuts. One of the major difficulties is the high perishability of the product. The major factors in post-harvest depreciation are moulding or rotting caused by fungi and the larval development of insects (Wells & Payne, 1975). Fungal infections often start in the larval galleries of insects (Wells & Payne, 1975), and many nuts become infected on the ground before picking. Some moulds are considered endophytes that colonise the fruits at various stages during their development but do not cause any symptoms of disease until after fruit fall (Washington et al., 1997, 1998). In Portugal, the traditional method of harvest is to allow the nuts to fall to the ground, and then harvest them manually or mechanically, with vacuum equipment. Interception of chestnuts in nets either on the ground or suspended above the ground is made in Italy and France mainly to ease and accelerate chestnut collection, but it is not a usual harvest method in Portugal.

Portugal is the fourth country in terms of worldwide European chestnut production (Figure 2.2). In 2004, chestnut culture in Trás-os-Montes occupied 85% of the national area devoted to chestnut production, and corresponded to 84% of the national production.

The region integrates three chestnut D.O.P. - Terra Fria, Padrela and Soutos da Lapa. It is the fruit with major significance in the portuguese import/export balance, with ratios of 1:6 (INE, 2005). There are no known statistics for processed chestnuts, but it is known that most of it is exported already processed.

Figure 2.2 Worldwide chestnut production (A) and area of production (B) of the 3 major producers and Portugal, for the year 2008 (data refer to sweet chestnut only) (http://faostat.fao.org, accessed 16.07.2010).