Hydrosostainable almondsnutritional, functional and sensory quality parameters and product acceptability in the european market

Resumen

Water is the most limiting factor in the Mediterranean Basin due to the rainfall shortage and higher rates of annual evapotranspiration (ET). Moreover, climate change is contributing to very frequent and severe drought day by day and agriculture sector needs maximum crop yield which is only feasible if optimum water supply is assured to maintain a normal physiological activity and transport processes. Among the different strategies to maintain the viability of the agricultural sector would be the introduction of drought-tolerant crops; or the implementation of water saving strategies, such as deficit irrigation (DI) that will seek adequate yields, maintaining, or even improving, the quality of the final product. Therefore, the main aim of this Doctoral Thesis, meant to investigate the effect of different deficit irrigation (DI) strategies on yield and physicochemical, functional, and sensorial parameters of raw and roasted almond (Prunus dulcis Mill. cv. Vairo), establishing those quality markers required further to identify/certify whether an almond is hydroSOStainable (growth under deficit irrigation strategies) or not; as well as evaluating the sensory profile and international consumers opinion regarding the hydroSOStainable almonds acceptance. The study was carried out along three seasons (2017-2019), in which, the following irrigation treatments were developed: (i) control treatment (covering 100% of the crop ET), (ii) 2 regulated deficit irrigations (RDI) treatments with a period of water stress during the kernel filling phase (with different stress levels depending on the stem water potential T2=-1.50 MPa and T3=-2.0 MPa) and full irrigated conditions for the rest of the year, and (iii) a sustained deficit irrigation (SDI) in which a lower amount of water was applied during the whole season (T4). Regarding the effect of DI on agronomical, morphological, and functional parameters of almonds, the results showed that almonds from moderated RDI (T2) were characterized by a redder color, a higher fat, K, glucose and total phenolic content (TPC), together with a greater content of individual phenolic compounds and proanthocyanidins (PAs), degree of polymerization, antioxidant activity, unsaturated fatty acid and total volatile content. Moreover, the TPC was positively correlated with the stress integral (SI), increasing with the water stress in plant. The phytoprostanes (PhytoPs) and phytofurans (PhytoFs) were quantified only in almonds growth under deficit irrigation conditions because in T1 these compounds were below de limit of quantification. In relation to the sensory profile of almonds and the international consumers acceptance, preference, and willingness to pay it was observed that (i) T2 almonds were characterized by an intense color, and intensity of both sweetness and hardness attributes; and that (ii) T2 almonds were the most liked by both nationalities due to the sweetness, almond flavor, and crispiness. Consumers are now more aware than ever on the importance of the optimization of water as they were willing to pay a higher price for the hydroSOStainable almonds, which means higher incomes and benefits for farmers. Additionally, it was observed that water stress accumulated during the studied seasons significantly affected the agronomical and quality characteristics of hydroSOStainable almonds displaying positive relationship with some parameters such as dry weight, color coordinates (L*a*b*), minerals (K, Fe, and Zn), organic acids (citric acid), sugars (sucrose, fructose and total sugars), antioxidant activity and fatty acids (linoleic, PUFA, SFA, PUFA/MUFA, among others). In contrast, the water stress in almonds showed a negative correlation with yield, water activity, weight, size, some minerals (Ca and Mg), fatty acids (oleic acids, oleic/linoleic ratio, MUFA and PUFA/SFA) and sensory attributes (size, bitterness, astringency, benzaldehyde and woody). In summary, K, Fe, Zn, sucrose, fructose, total sugars, antioxidant activity and the fatty acids can be considered important markers for hydroSOStainable almonds detection. Moreover, when almonds were processed it was observed that a heat treatment of 170 ºC during 10 min in a convection oven were the optimum roasting conditions from an aromatic, descriptive and affective point of view for the cv. Vairo almonds. Besides, deficit irrigation led to sweeter almonds with higher intensity of roasted almond and nutty notes, and with greater content of aroma compounds comparing to the control. According to the results obtained in this research work, it can be concluded that controlled deficit irrigation strategies can be considered an important tool to reduce the water consumption in almond crop, with significant improvements in fruit bioactive compounds with potential beneficial effect on human health. Moreover, it has been proved that controlling the stress in almond trees can increase both the irrigation water productivity and the farmers profit; by producing environmentally friendly products, better valued by the consumers. In this scenario, government and industry actions might emphasize on providing the right information to the consumers regarding hydroSOStainable products, while agricultural sector might produce these foods helping to combat the water scarcity worldwide.