Although there are already forest producers reconciling the production of pine nut and resin in their stone pine (Pinus pinea L.) areas, the implications that resin can have on the quantity and properties of pine nuts are little known, which is why the topic has begun to attract the attention of Portuguese researchers.
In this context, a study carried out at Herdade da Esteveira, in Alcochete, indicates that it is feasible to produce pine nuts and resin, without the resin affecting the chemical composition and food safety of the pine nut.
The conclusions were made known in the master’s thesis “Effect of resin on the chemical composition of stone pine”, carried out at ISA – Instituto Superior de Agronomia of the University of Lisbon, after several years of trials in which pine cones were collected from resinated and non-resinated trees, and the chemical composition of the respective pine nuts was analyzed. “No differences were observed in the chemical composition of pine nuts from resin and non-resinated trees,” says José dos Lóios Angelino in his thesis, carried out under the supervision of professors Paula Soares and Ana Alves.
The most common resin method in Portugal (and Europe) requires the application of a stimulant to delay crystallization and thus increase the resin runoff time. This stimulant, which is applied to the incision area, may contain sulfuric acid, so another of the questions under study was to determine whether there were traces of this acid in the pine nuts of resinous trees. Here, too, the answer was negative: “no traces of sulfuric acid were observed in the spectra of pine nuts from resin-bearing trees”, which reinforces the possibility of producing pine nuts and resin in the same tree.
The stimulating paste applied to the incisions to make the resin flow contains sulphuric acid, although biological acids that may have the same stimulating effect and that pose less risk to the activity are already being tested. This is a work that is being developed by the Integrated RN21 project – Innovation in the Natural Resin Sector to Strengthen the National Bioeconomy. In parallel, more effective resin methods that promote greater purity of the collected resin are also being tested, such as closed bag resin.
Is the yield of pine nuts influenced by resining? More data is needed
Another hypothesis studied was whether the resining of stone pine would affect the yield in terms of pine nut kernels. For this purpose, the production of resin and non-resinated trees was analyzed, considering the yield of white pine nuts in relation to the weight of the respective green pine cones.
Interestingly, resin trees have a higher yield than non-resinated trees. However, this result needs to be validated with more data, because in this study, it was not possible to analyze the yield of resin trees before starting resining, in order to know the yield differences of each one before and after. Thus, to deepen the effect of resin on yield in pine nut kernels (also called white pine nuts), the study suggests the installation of permanent plots in stone pine stands, so that this comparative evaluation can be made over several years.
As a pine cone takes three years to form, and this trial ended in the 2021/22 campaign, it was not possible to collect enough pine nuts to carry out palatability (taste) tests, as this campaign corresponded to a year of counter-harvest, that is, of low production. It should be remembered that several species, including stone pines, intersperse counter-harvest years with others of greater fruit production – the harvest years. Therefore, additional studies are also needed in this area, including sensory analysis and palatability studies to determine whether differences in appearance and taste are identified between resin and non-resin pine nuts.
Although there are still some questions to be deepened and confirmed, the results of this study have shown that it is safe and feasible to reconcile two productions, creating a double source of return for owners who invest in stone pine. Another study from 2022 – the Potential of Resin Harvesting in Portugal – reinforces the idea that the joint exploitation of pine cone, pine nut, and resin is a source of income to be considered, in a logic of multifunctionality of forest spaces, but warns that there is a lack of forestry models specifically oriented to the co-production of pine nuts and resin.
Resin with increasing appreciation
In Portugal, maritime pine is, par excellence, the resin species, but with the increase in the stone pine plantation area – which went from 120 thousand hectares to 194 thousand between 1995 and 2015, according to the 6th National Forest Inventory (IFN6) – there has been an increase in the resin of this species: it was estimated that 2 thousand hectares of stone pine were already resinated in Portugal (about 7.7% of the total resinated area), in 2021.
“It is expected that the proportion of stone pine resin will continue to increase in the coming years in Portugal,” says Resipinus – Association of Distillers and Resin Explorers, which justifies the trend with the need to compensate for the reduction in the area of maritime pine.
As part of another project – SustForest Plus – plots were also installed and some stone pines were resined in two locations. At Herdade da Esteveira, in Alcochete, resinated stone pines produced an average of 4.6 kilograms of resin per tree in 2018 and 5.2 kilograms in 2019, although with very significant variations from tree to tree. In Chamusca, the average value of resin obtained was lower, 2.1 kg per tree, as revealed by the study “Potential of Resin in Portugal”.
The average price per kilogram of resin has evolved positively, according to data from INE – National Statistics Institute: it remained above 1.3 euros between 2021 and 2023, a threshold never reached until then, and which denotes a significant appreciation compared to what was recorded in the previous 20 years. For example, in 2003, the price per kilogram was only €0.42, and in 2013 it had increased to €1.09.
In recent years, the amount of resin produced has seen significant fluctuations: the highest productions were recorded between 2014 (8056 tons) and 2017 (8004 tons), years in which they were well above the quantities produced between 2021 and 2023. In these years, the quantities have decreased, falling from close to 6 thousand tons to the aforementioned 5354 tons in 2023.
It should be remembered that Portugal was the world’s second-largest exporter of resin in the 1970s. At the time, the national production of resin was more than 100 thousand tons, and the area of pine forests was more than 1 million hectares.
Pinion: high value, high competition
Unlike resin, not much statistical data is available on pine nut production in Portugal.
A study by Agro.Ges (2023) estimated pine nut production at 842 tons in the 2021/22 campaign, significantly below the values calculated for the two previous campaigns, in which production exceeded 1200 and 1600 tons, respectively, in 2019/20 and 2020/21.
The estimate was made considering a yield of pine cones in pine nut kernels between 3.5 and 4.2%, according to what is indicated in the Guide to Harvesting and Marketing of Pine Cones (2014), a document by UNAC – Union of Mediterranean Forests that warns of variations in these percentages depending on the area of origin, the year of harvest and weather conditions.
According to UNAC, the 2022/23 campaign had low average yields due to the sequence of hot and dry years that preceded it.
In the pine nut sector, there are three products: the pine cone, the black pine nut, and the pine nut kernel or white pine nut. The pine cones are harvested from the trees between December and March, and are subjected to an initial drying. In a first transformation, the pine cones are opened (in the open air or with artificial heat) and the pine nuts with shell – black pine nut – are removed. This pine nut undergoes a new transformation and processing to separate the shell from the kernel, obtaining the so-called white pine nut.
As for its value, pine nut prices on the production market (SIMA – Agricultural Market Information System) have fluctuated in recent years: the highest appreciation happened in 2020, when the most frequent maximum value reached 68.7 euros per kilogram, but has fallen since then, and the most frequent prices in 2023 were close to 50 euros per kilogram.
It should be remembered that this is one of the most valued nuts, both in price and nutritional quality. The Portuguese pine nut (and the Mediterranean basin) comes only from the stone pine (Pinus pinea) and is recognized for its nutritional characteristics, and there is even an application for registration of a PDO – Protected Designation of Origin for the Pine Nut of Alcácer do Sal by UNAC. However, their production and value are susceptible to several factors, such as:
Attack by pests, such as the pine cone sucker (Leptoglossus occidentalis), anticipating that new pests will arrive in Portugal, such as Toumeyella parvicornis, already identified in Italy and France.
Competition from Pinus pinea pine nuts coming from new producer markets. The species has been widely planted in regions with a climate similar to that of Portugal – in areas of Chile and New Zealand, for example – which are gaining relevance among pine nut producers and bringing increasing volumes of pine nut kernels to the international market.
Competition of pine nuts from pine species native to other regions of the world. Often called Asian pine nut, it comes from different species of pine trees, which we don’t have in Portugal, and has slight differences in shape, color, and size, as well as composition and flavor, compared to “our” pine nut.
Among them are, for example:
Pakistani pine (Pinus gerardiana), a species common in parts of Pakistan, China, Tibet, India, Kashmir, and Afghanistan. For example, the pine nut is longer than that of the stone pine,
Pinus koraiensis, known as the Korean pine, is also native to the highlands of China, Japan, and Russia. The pine nut has a more triangular shape.
Chinese pine (Pinus armandii), native to eastern China, Japan, Korea, and parts of Siberia.
Siberian pine (Pinus sibirica), from Mongolia and Russia.
Even with these constraints, the pine nut remains a valid investment for many forest producers. Production in the Mediterranean continues to be led by Turkey, Spain, and Portugal. Globally, it is China that stands out as the largest producer (about 30% of global production in the 2022/23 campaign), followed by Russia and North Korea. Italy and the USA are the largest consumers in the world.
In addition to visible physical differences, pine nuts from the various species of Pinus are distinct in their composition and flavor.
The combined production of pine nuts and resin can complement the income of producers, with resin supporting the return of pine nuts in counter-harvest years and bridging other factors that can influence the profitability of this crop, such as the price variation resulting from the greater quantity of pine nuts coming from other regions of the world.
The article was originally published in Florestas.pt.
Learn more here