Hemp seeds could be considered a sodium-free food, as whole and hulled hemp seeds contained less than 5 mg/100 g.Notwithstanding the foregoing, the real contribution of hemp seeds to NRVs is lower because their serving size is approximately 30 g.As it can be seen in Fig.1b, whole hemp seeds could be considered a source of potassium and calcium, but the contribution to NRVs of 30 g would be only 9% and 7%, respectively.However, the contribution to manganese and copper NRVs of a serving size were higher than 40% in both whole and hulled hemp seeds.The contribution to manganese NRV stood out because the consumption of 30 g of whole hemp seeds would exceed an intake of 100% NRV.In this view, the interpretation of the claims can be confusing for the consumer due to the fact that they are linked to the presence of these compounds in 100 g of seeds without taking into account the serving size.Phytate content, expressed as g PAE/100 g, is shown in Table 3.The average phytate content in whole hemp seeds was 2.80 g/100 g, being ‘Carmagnola’ and ‘Tiborszallasi’ the varieties with the lowest phytate content, 2.66 mg/100 g, and ‘Fedora 17’ the variety with the highest, 3.08 g/100 g.The phytate content was higher in hulled hemp seeds, 4.00 g/100 g on average.Mattila et al. reported a phytic acid content of 3.5 g/100 g, which was higher than the phytate contents of this work.Their result was expressed in dry matter, so it would be lower if expressed in fresh weight and closer to the maximum valued obtained in this work, which was higher than 3 g/100 g.Schultz et al. analysed different varieties and their average value was 2.67 g/100 g, very close to the average value obtained in this work.It was not possible to find previous studies about phytate content in hulled hemp seeds.

Based on phytate and phosphorus content, phosphorus from phytates  and the proportion of phosphorus from phytates with respect to total phosphorus content were calculated.The phosphorus from phytate calculation is indicative, as different phytates have a different number of phosphate groups and they are expressed in this work as PAE.So,grow tent indoor the proportion of phosphorus from phytates with respect to total phosphorus content is also indicative, but it provides information about phosphorus bioavailability.In whole hemp seeds, the proportion of phosphorus from phytates with respect to total phosphorus content was higher than 90%, and it was even higher in hulled hemp seeds.These results indicate that almost all of the phosphorus is found as phytates in hemp seeds, so its bioavailability is supposed to be low.From phytate, iron, and zinc contents, the phytates/zinc and phytates/zinc molar ratios were calculated, according to Dahdouh et al., and included in Table 3.It is considered that iron bioavailability is affected by a phytates/iron molar ratio above 1 , and whole and hulled hemp seeds showed values higher than 20 and 30, respectively.In the case of zinc, a phytates/zinc molar ratio above 15 is considered to compromise its bioavailability.All the samples analysed had phytates/zinc molar ratios much higher than 15, even above 60.The fractional absorption of phosphorus is higher than that of calcium and it is recommended a calcium/phosphorus molar ratio should range between 1.4 and 1.9 for a suitable equilibrium and absorption of both elements.Considering the calcium and phosphorus contents shown in Table 2, the calcium/phosphorus molar ratio ranged from 0.12 to 0.20 in whole hemp seeds and from 0.04 to 0.07 in hulled hemp seeds.These values were very low, especially in hulled seeds, due to their higher phosphorus content and their lower calcium content.All values were much lower than the recommendation, so the calcium absorption could be compromised because of the high content of phosphorus.

However, it has been previously said that phosphorus contained in hemp seeds is difficult to assimilate because it is in the phytate form, so the calcium/phosphorus molar ratio would not represent a real competition in terms of absorption.Another anti-nutritional compound that could reduce the calcium bio-accessibility in plant foods is oxalic acid.It is said that an oxalic acid/ calcium ratio higher than 2.25 could compromise calcium absorption.Considering the calcium contents shown in Table 2 and the oxalic acid content previously reported by Alonso–Esteban et al., the oxalic acid/calcium ratio was lower than 2.25 in all samples, with average values of 0.56 and 1.27 in whole and hulled hemp seeds, respectively.So, the presence of oxalic acid in hemp seeds could not compromise calcium bio-accessibility.Oxalate/calcium molar ratio would be even lower due to the higher molecular weight of oxalates, so there would be no risk according to Israr et al. and Udomkun et al., who indicate that an oxalate/calcium molar ratio higher than 2 could be hazardous.The impeachment of phosphorus, iron, zinc and calcium absorption due to their chemical forms and the presence of anti-nutrients, reveals that using just the numerical contents of nutrients to make nutritional or health claims in foods, is not a suitable tool for a proper information to consumers, since their contents may not be totally available for the human body.The bio-accessibility of other mineral elements would not be compromised by phytates or oxalates.However, future studies concerning mineral element bio-accessibility and bio-availability in whole and hulled hemp seeds should be carried out in order to evaluate if they are a good dietetic source of mineral elements.Hemp  is a plant well known for its content of bio-active cannabinoids, a group of secondary metabolites unique for the genus Cannabis.These compounds are produced by specialized glands in the leaf epidermis, occurring more densely in the inflorescence and less in the leaves.Four cannabinoids are present at high quantities, cannabidiolic acid  and Δ-9-tetrahydrocannabinolic acid,which decarboxylate at elevated temperatures to form cannabidiol  and Δ-9-tetrahydrocannabinol  respectively.Cannabinol  is a degradation product of THC.Due to their interactions with the human endocannabinoid system, these compounds are of special interest for their therapeutic potential in neurological disorders.

THC is a psychoactive compound with effective doses between 10 and 20 mg THC, while the other three cannabinoids are nonpsychoactive compounds or exert only a low psychoactivity.Therefore, it is the presence of THC in hemp food products that is of special interest for food control purposes.However, it is not only the original THC content of the starting material that is being considered, but also the formation of additional THC due to conversions in the course of industrial processing or preparation by the consumer, such as that of THCA into THC.It is known that hot temperatures increase THCA decarboxylation to form THC, whereas this conversion does not occur in the human body.Formation of THC could also possibly occur by conversion of CBD under acidic conditions.However CBD-to-THC conversion was never actually observed, neither under specific light or temperature regimes nor in a simulated gastric juice.Consequently, THC formation by this route is likely not relevant for food products.In Austria, cultivars of Cannabis sativa with a THC-content below 0.3% are not regulated by the Narcotic Substances Act.However, cultivation in Europe is only subsidized when using cultivars from the Common EU Catalogue of Varieties of Agricultural Plant Species.In a fiber hemp, CBDA is the major cannabinoid.However, even these varieties are never completely free of THC.That is one of the reasons why EFSA assessed the human exposure to THC and established an acute reference dose  of 1 μg Δ9-THC/kg body weight for the use of fiber type hemp in food.Hemp leaves have become very popular as ingredients for herbal teas , either as hemp-only tea or as part of tea mixtures.These herbal teas are usually prepared as infusions by pouring boiling water on the plant material and allowing to steep for a defined period of time.The preparation of herbal infusions is not well standardized, specifically, water temperature will shift while cooling down during the extraction process.It can be expected, that because of their lipophilic nature, even under optimum extraction conditions, only a fraction of the cannabinoids are transferred into a herbal infusion.However, there is no validated, generally recognized method for analyzing cannabinoids in infusions, partially due to issues in recovering lipophilic compounds from water.In order to address the former challenge a response-surface modelling approach was used to cover a range of water temperatures, water volumes and steeping times for the preparation of an infusion.To address the latter, rather than attempting to determine the cannabinoid contents in the tea liquid, the cannabinoid contents of the starting plant material before infusion and the residue after infusion were compared and loss or gain of the major cannabinoids for this aqueous extraction was calculated.The upper leaves of Cannabis sativa L.var.‘Fiona’ were harvested before flowering and dried at room temperature.

Each extraction experiment was performed with an analysis sample of approximately 1.5 g that represented a portion of a laboratory sample of approximately 800 g.These portions were arrived at by dividing the total laboratory sample with a riffle divider in nine serial steps, grow tent hydroponic at each step into halves.In order to establish that the resulting portions were actually true aliquots of the original laboratory sample, 14 randomly chosen presumptive aliquots were tested for their cannabinoid contents.For CBD and CBDA the relative standard deviations were 3.8% and 2.7%, respectively.For THC and THCA the relative standard deviations were 3.6% and 3.0% respectively.From this we concluded that our laboratory analysis samples were in fact true aliquots, that the measured cannabinoid values were in fact reliable base values for the following recovery experiments and that the observed RSD% values for repeatability likely represented but measurement uncertainty.Food products prepared from fiber-type hemp cultivars, poor in THC, but rich in CBD, have become very popular.Besides hemp oil, beverages like hemp beer and CBD rich food supplements, infusions from inflorescences and/or leaves that are widely used either as single ingredient or in herbal tea mixtures.Lipophilic cannabinoids are only marginally soluble in water, and to some extent, the cannabinoids in a herbal infusion may become adsorbed onto small particles suspended in the tea.Thus, due to their lipophilicity and potential adsorption issues, analysis of cannabinoids in an infusion is difficult and not reproducible.Therefore, this paper focuses on the quantitation of cannabinoids in the residue of the hemp leaves after preparing the infusion, using HPLC/UV.In the process of preparing an infusion of plant material, the solvent will extract the soluble constituents thus reducing the remaining content in the plant residue, but no extraction occurs for insoluble compounds.In our case, the contents of CBD and THC in hemp leaves residues after infusion were even increased, when compared to the starting plant material, presumably due to decarboxylation of their corresponding acid-forms at higher temperatures.Increase or decrease of a particular cannabinoid’s content in the hemp leaf residues appear primarily related to the lipophilicity of the compound  of 5.95 , 6.25 , 6.33 and 6.63 and the extent of decarboxylation.

Some peculiar differences were observed for different extraction temperatures regarding the cannabinoids content before and after tea preparation.Taschwer and Schmid  found in plant material dried at 50 ◦C no conversion of THCA to THC, whereas complete decarboxylation was recorded at 100 ◦C and 150 ◦C, but only after 2 h and 1 h, respectively.Therefore decarboxylation cannot be expected to play an important role when preparing a herbal infusion by pouring boiling water over the plant material with a steeping time of 10 min , but has to be considered for decoctions.THC may also degrade to CBN under certain conditions.However, degradation of THC to CBN is insignificant at boiling temperature of water and 15 min extraction time , as also confirmed by our study.The solubility of THC in water at 23 ◦C is 2.8 mg/l.The solubility of the other cannabinoids in water should theoretically increase in the order THC < THCA < CBD < CBDA  but are not yet experimentally proven.Solubility of cannabinoids at higher water temperatures is also unknown, but likely increasing as e.g.observed for solubility of saturated fatty acid in water.However, a spiking experiment with pure THCA and THC to boiling water  showed only 63% recovery or THCA  and only 17% for THC.Calculating for better comparability the differences between hemp leaves before and after tea preparation at 43 ◦C for 15 min in a volume of 150 ml  resulted in 26.46 mg/l CBDA, 1.24 mg/l CBD, 0.82 mg/l THCA and 0.37 mg/l THC.