Challenges and Advances in the Production of Export-Quality Macadamia and Its Integral Use with Green Technologies

*Laura Graciela Mereles, Mario Smidt, Karen Patricia Martínez, Eva Eugenia Soledad Coronel, Edelira Velázquez and Laura Correa*

#### **Abstract**

Macadamia nut is an alternative crop for agricultural production in tropical Latin American countries. Its cultivation in itself constitutes a challenge for countries with high relative humidity temperatures, especially in the postharvest period. Environmentally friendly technologies suggest a comprehensive nut in shell (NIS) and kernels treatment, taking advantage of the waste generated in the drying process, critical point. This chapter explores the methods of the literature and those applied in local research for the integral use, drying of macadamia nuts, and their processing until obtaining products of high nutritional quality (dried nut and oil) and with clean technologies applicable to small producers.

**Keywords:** *Macadamia integrifolia*, production, composition, quality, analysis, oil extraction, byproducts, tropical countries

### **1. Introduction**

Since the first scientific evidence on the frequent consumption of nuts on health, macadamia nuts, produced in various tropical regions of the world since their origin in Australia, have gained great interest as part of a healthy diet. In vivo studies in rats, mice, and humans have shown that macadamia nut oil reduces total cholesterol, low-density lipoprotein (LDL) cholesterol, body weight, and body mass index, inhibits the development of sucrose−/fructose-induced hepatic steatosis, and attenuates adipocyte hypertrophy and inflammation in adipose tissue and macrophages [1]. In addition to the high concentration of monounsaturated, the main source of health nutrition and pharmacological properties of these oils comes from their minor components that are phytosterols, tocopherols, phenols, squalene, carotenoids, and others [2]. Its antioxidant potential is attributed to these compounds together. Dried macadamia nuts have shown good total antioxidant capacity and may be useful when

consumed alone or in combination with traditional pharmacotherapy to reduce the risk of cardiovascular disease. Intervention studies consistently show that the consumption of macadamia nuts causes a decrease in plasma total cholesterol and LDL cholesterol, and despite its high fat content, the regular consumption of macadamia nuts has been shown to have no effect on the body weight [3]. These studies have been carried out using macadamia nuts which, due to their unique composition, are influenced by the quality of the kernel, so the production system has a major impact on their commercialization and health effects.

The great challenge of macadamia production for the world has been to maintain sensory and nutritional quality, due to its high composition of oils, which are susceptible to oxidation and require a careful system of cultivation, selection, drying, and packaging to reach the consumer with all their nutritional and bioactive properties [4]. Compositional differences observed in different studies on macadamia nut and oil could be explained by the variation in cultivars, growth conditions, harvest time, degree of maturity, and storage conditions [1]. Several studies have addressed this problem, and its composition has been studied in different production regions, which opened a field of research on its sustainable production and use of green technologies that generate new markets with which the macadamia nut has become a product of great value based on these experiences [5–8].

The macadamia producers par excellence are Australia (where it originates from), South Africa, and the United States [9]. In South America, the macadamia nut represents an alternative crop to those of great expansion such as soybean or corn; however, it is a noble crop that allows the use of the soil in the spaces left by the treetops, with the production of other foods such as pineapple or medicinal herbs [10]. This, added to the added value that can be obtained from its integral use, from the exocarp (green) and the mesocarp (brown) of the fruit and the dried and split nuts (kernel) that are used to obtain oil, is viable and attractive alternatives for small- and medium-sized producers [5, 11, 12]. The rich fatty acid composition of the oil obtained from macadamia nuts allows its diverse use in many industries, i.e., cosmetic and pharmaceutical [11]. Macadamia nuts are marketed in the export market mainly in two forms: shelled nuts (kernel) and nuts in shell (NISs) (**Figure 1**). The market by application

**Figure 1.** *Cross section of the NIS with the almond (kernel) inside and the woody shell outside (mesocarp).*

*Challenges and Advances in the Production of Export-Quality Macadamia and Its Integral Use… DOI: http://dx.doi.org/10.5772/intechopen.105000*

can be divided into snacks, confectionery and bakery, cosmetics, and others. The international market by region is mainly distributed in North America (the United States, Canada, and Mexico), Europe (Germany, the United Kingdom, France, Italy, Russia, and Spain), Asia-Pacific (China, Japan, Korea, India, Australia, and Southeast Asia), South America (Brazil, Argentina, and Colombia), and the Middle East and Africa (South Africa, the United Arab Emirates, and Saudi Arabia). Many times, the internal challenges and opportunities of the smallest producers are not the same as for the largest producers.

In this chapter, we address the production of nutritional quality macadamia nuts, from the postharvest processing, drying, and packaging system. Its comprehensive use in tropical countries, based on the data established in the literature and the work team's own results, opens a series of accessible low-cost alternatives and green technologies based on the lessons learned for their production in tropical countries with often limited resources.

#### **2. Macadamia nut and oil composition**

The nut is rich in protein and has a high energy content, outstanding organoleptic and nutritional characteristics, and a high amount of oil (~ 74% w/w) [13, 14]. Its use for cooking food is limited, and it is mainly used as a flavoring oil [15]. In addition, dried macadamia nuts (kernel) contain other important dietary components, including protein (7.2–10.4%), good levels of dietary fiber (6.2–8.6%), fat-soluble vitamins (especially alpha-carotene), minerals (Mg, Ca, and K), and phytochemicals (phytosterols). They are low in carbohydrates (0.5–13.8%). A comparative study of the centesimal composition and lipid profile of 22 varieties of *M. integrifolia*, grown in Itapirá (Brazil), showed large variations in composition with respect to the composition of macadamia from other origins; however, the samples were taken from very young trees (7 years) [7]. After 8 years of cultivation, adult trees are considered with a more constant composition of nuts. In another study, it was observed that tocotrienols and squalene were largely affected by varieties and their content in seven macadamia cultivars produced in Hawaii ranged from 31 to 92 and 72 to 171 μg/g of oil, respectively [6]. With several studies on its chemical composition, it is now known that it can vary greatly due to the influence of the type of cultivar (genetics), the ripeness of the grain, the time of harvest, the geographical location, and the conditions of the crop [1]. Macadamia nut proteins have all the essential amino acids, and their limiting amino acids include tryptophan, lysine, and threonine [16]. The sugar content is mainly represented by fructose, glucose, maltose, and sucrose. The cultivars differ in the sucrose content of the nut, but not in the content of reducing sugars [17]. Regarding the mineral content, macadamia nuts are considered a source of magnesium, calcium, and potassium [13]. Macadamia nuts from Australia have been reported to contain 5.77 mg/100 g of iron and low levels of zinc and copper [18].

Regarding the oil, in most published studies, the content of monounsaturated fatty acids (MUFAs) predominates, among which oleic acid C18:1 and palmitoleic acid C16:1 stand out. Other monounsaturated fatty acids, such as gondoic acid C20:1 and erucic acid C22:1, are also reported by some authors among the components of macadamia oil [19, 20]. Macadamia nut oil has various food and nonfood applications including food fortification, development of skin, hair, and healthcare products. Rich in monounsaturated fatty acids (oleic and palmitoleic acid), macadamia oil also contains a significant concentration of bioactive phytochemicals

including β-sitosterol, α-tocopherol, α-tocotrienols, ρ-hydroxybenzoic acid, and caffeic acid [1]. Macadamia oil contains significant concentrations of phytosterols (~165 mg/100 g), especially β-sitosterol in 82% with levels from 96.9 to 151 mg/100 g of oil. Other components identified in this fraction are campesterol (11.6 mg/100 g), stigmasterol (2.2 mg/100 g), and avenasterol (16 mg/100 g) [20–22]. A study carried out on different oils from nuts and avocado and sesame describes that macadamia nuts contain more phytosterols (184 mg/100 g oil) than oils from other nuts such as walnuts (165 mg/100 g oil), almonds (122 mg/100 g oil), and hazelnuts (89 mg/100 g oil); however, avocado and sesame oils contain much higher amounts (434 and 620 mg/100 g oil, respectively) where the majority component is always β-sitosterol [20]. In addition, the oil has good oxidative stability, which can vary with the harvest season and the crop [17]. There is a positive correlation between antioxidant activity and oxidative stability of the oil. Although there is considerable variation in the oxidative stability of macadamia oil among the studies found in the literature, it is always related to the composition of phytochemicals. In a study, the chemical composition and antioxidant capacity of macadamia oils obtained from 15 cultivars of *M. integrifolia* were comparatively analyzed, and the analysis strongly supported the positive contribution of polyphenols and squalene to the antioxidant capacity of macadamia oils [5].

All these bioactive compounds in macadamia nuts and its high levels of monounsaturated fatty acids make them beneficial for health with frequent consumption, and at an industrial level, they allow the nuts to be minimally processed or industrialized for the production of oil and defatted meal [11].

The comparison of tocopherols, tocotrienols, and squalene content in seven varieties of *M. integrifolia* revealed that macadamia oil has significant amounts of tocotrienols (46.5–91.6 μg/g oil) and squalene (72.4–171 μg/g oil), with variations in the total content of tocotrienols between harvests [6], suggesting a considerable environmental effect on the accumulation of these phytochemicals during nut development. Compared to other nuts, they tend to contain the lowest levels of tocopherols [23, 24] despite being the most stable oil compared to almond, hazelnut, and walnut oils. This seems to indicate that its stability is due in part to its mainly monounsaturated fatty acids (MUFAs) profile, with low percentages of polyunsaturated fatty acids (PUFAs), rather than to the composition of its antioxidant compounds. High oleic oils offer excellent oxidative stability and low-temperature flow properties for many applications. In the vegetable kingdom, oils with a high content of natural oleic acid stand out, such as avocado, macadamia, and olive oils. Macadamia oil has the highest monounsaturated oil content (80%) among common edible oils, followed by olive oil (74%) and avocado (65%) [2]. However, roasting nuts, a process normally used to improve sensory characteristics such as texture and flavor, can alter the fatty acid profile and minor components of the nuts depending on the roasting temperature [25], so recommendations indicate that its healthiest consumption is as dry nut, without roasting.

Macadamia nuts are one of the main sources of palmitoleic acid and can serve as the main dietary source of palmitoleic acid in the diet. Palmitoleic acid is an unusual omega-7 monounsaturated fatty acid found naturally in high levels in macadamia plants (17–20% of the oil) and shares the same structure as the endogenously synthesized form of palmitoleic acid in humans, for which it receives a lot of attention regarding metabolism and health. Recently, palmitoleic acid has been shown to be a lipokine with many beneficial health effects, including anti-inflammatory properties, reduction in body weight, blood glucose, and triglyceride levels, and

#### *Challenges and Advances in the Production of Export-Quality Macadamia and Its Integral Use… DOI: http://dx.doi.org/10.5772/intechopen.105000*

improvement in insulin sensitivity [2]. The importance of regulating its content as an indicator of its nutritional quality and commercial value has been discussed, especially given its ability to increase insulin sensitivity and reduce the risk of diabetes. Other described effects on the pathogenesis of obesity, liver, and cardiovascular health remain unclear [26].

On the other hand, nuts such as peanuts or walnuts may present certain food intolerances; in the case of macadamia nuts, a systematic proteomic description has recently been presented. The most abundant proteins belong to the 11S globulins and the 7S vicilins. In silico analysis revealed homology and linear epitope similarities with known allergens from lupine, walnut, and peanut, among others. This opens a path in clinical diagnosis and food analysis toward possible protein candidates with allergenic and cross-reactive potential for further immunoglobulin E (IgE) characterization studies of allergenic foods [27].
