In order to monitor the effects of reformulation and heating treatment on the lipid oxidation of beef burgers, lipid oxidation was measured in all samples, before and after cooking.Significant differences were obtained with the addition of GEs, in both raw and cooked samples.In raw samples, burgers reformulated with chia oil registered higher TBARS values than the control sample, being burgers with the highest replacement level which showed the highest TBARs values.In fact, BCh50 samples showed 3.5 times more oxidation than the control sample.Burgers reformulated with GE with hemp oil showed similar TBARs values than control.This fact was in concordance with several authors who reported that the use of GE elaborated with vegetable oils as animal fat replacement in meat products might be complex due to the high oxidation susceptibility of these unsaturated oils.The differences in the lipid profile of the oils, the content of polyunsaturated fatty acids, and the temperature used to generate oleogels or gelled emulsions could affect the MDA levels.It must be noticed that TBARS values in burgers reformulated with GE elaborated with amaranth flour and hemp oil as well as the burgers reformulated with GE elaborated chia oil were below the malonaldehyde limit for acceptability reported by Trindade, Mancini-Filho, and Villavicencio for loss of sensory attributes and perception of oxidation by consumers.However, it is important to highlight that cooked burgers reformulated with GE elaborated with amaranth flour and chia oil showed values above the threshold limit for consumer acceptability.The influence of the addition of GEs on sensory attributes of raw beef burgers is shown in Table 8.Relevant parameters affecting consumer purchase were measured, such as “color”, “rancid aroma” and “product appearance”.
Panelists did not detect differences between control and reformulated burgers for any of the three evaluated parameters.This result agreed with the instrumental color parameters,hydroponic grow tent where L*, b* and h* values had no differences between samples and the rest of color parameters showed small differences which were statistically significant but without practical significance.In the case of cooked samples, juiciness, chewiness, fat sensation, graininess and general acceptability were evaluated.The only attribute that showed differences between samples was graininess: BCh25 and BH25 showed the highest score without statistical differences between them , while control sample had the lowest.These results agreed with the instrumental analysis since textural analysis revealed only differences in cohesiveness between some samples.For the preference test, control sample and BH50 were the most chosen.It has to be mentioned that the information about the nutritional improvement achieved in reformulated burgers was not communicated to panellists and that could be relevant and affect their sensory attractiveness.Hemp is a widespread herbaceous plant native from Central Asia that belongs to the Cannabaceae family.This plant could be considered as one of the first crops because it is thought that it was cultivated in China 8500 years ago.Hemp has been traditionally cultivated with industrial, medicinal and food purposes.Its fibre was obtained from stems, specifically from the phloem, and it has been widely used, especially in the shipbuilding industry.Female flowers were useful because of their pharmacological properties, and seeds were used mainly as food.Hemp phytochemistry is quite complex and cannabinoids are its most distinctive compounds.They are produced almost entirely in glandular trichomes, which are commonly located in the bracts of female flowers.Nevertheless, other parts of the plant, such as seeds, could contain a small quantity of cannabinoids , which is subject of regulation in different countries of the world.
The most important one is Δ9 -tetrahydrocannabinol , due to its psychoactive properties, and only varieties with low Δ9 -THC content can be cultivated.Nowadays, the consumption of hemp seeds and derivative products is increasing.Whole hemp seeds are used as a raw material, but could be consumed as food as well, and hulled hemp seeds are commonly marketed as functional food.Hemp seeds contain large amounts of fibre, fat, and protein, at 27–40, 25–35, and 18–28 g/100 g, respectively.They contain significant amounts of linoleic acid, which represents 50% of total fatty acids, 16–19% of α-linolenic acid, 12–17% of oleic acid, and other minor fatty acids, being remarkable the presence of γ-linolenic acid.In addition to nutrients, hemp seeds contain bio-active compounds which confer a biological potential, such as antioxidant, antimicrobial and cytotoxic properties.Chen et al. attribute some of these bio-active properties to phenolic compounds, the main being lignanamides, such as cannabisins.The studies about mineral elements in hemp seeds are scarce, but Callaway and Mihoc et al. reported an interesting content of some of them, such as phosphorus, potassium, magnesium, calcium, iron, zinc, manganese, and copper, which are essential dietary elements for mammals and are involved in many physiological processes.Mineral element bioavailability could be compromised by different anti-nutrient components in foods, such as phytates and oxalates, which are present in hemp seeds.Phytic acid is the main storage form of phosphorus in seeds and it can form insoluble complexes with some cations, such as calcium, magnesium, iron, and zinc.The chelating capacity of phytates is especially damaging in the case of iron and zinc, and their deficiencies constitute a significant public health problem.The absorption of calcium of plant origin is impaired by the presence of oxalic acid, which promotes the formation of insoluble calcium oxalates.The objectives of this study were to determine the mineral element content of different varieties of whole hemp seeds and commercial hulled hemp seeds, as well as the phytate content, which is closely related to the mineral element bio-accessibility.Phytates were determined by an indirect iron complexometry with sulfosalicylic acid like an indicator of the titration endpoint, according to Romero–Aguilera et al..The extraction was carried out under magnetic agitation for 90 min from 2 g of sample with 40 ml of HCl 0.4 M, which contained Na2SO4 5%.
The resulting suspension was centrifuged at 1890g during 8 min, and the supernatant was filtered and made up to 50 ml with the extraction solution.After that, 20 ml of the extraction solution, 20 ml of FeCl3 0.02 M , and 20 ml of sulfosalicylic acid 20% were added to 25 ml of the extract, and the mixture was made up to 100 ml with distilled water.Blank was prepared in the same way, but 25 ml of the extraction solution were used instead of the extract.The solutions were heated for 15 min in a boiling water bath and then they were cooled in an ice bath.One aliquot of 20 ml was pipetted together with 200 ml of distilled water and 1.5 g of glycine were added.This solution was heated at 70 ◦C and titrated with EDTA 10 mM while still warm until the solution turned yellow.All the volumes obtained from the titration of the samples and standards were subtracted from the blank value, obtaining the amount of EDTA equivalent to the complexing activity of.the phytates in the sample.For quantification purposes, a calibration curve was built using a commercial phytic acid standard.The analyses were performed in triplicate and the results were expressed as g of phytic acid equivalents /100 g.The results of mineral element analysis of both whole and hulled hemp seeds are shown in Table 2.Regarding macroelements, sodium was the least abundant, with an average value of 2.75 and 1.41 mg/100 g in whole and hulled hemp seeds, respectively.All the samples contained less than 5 mg/100 g.On the other hand, phosphorus was most abundant one, with an average value of 871.2 and 1099.5 mg/100 g in whole and hulled hemp seeds, respectively.Phosphorus content was lower in whole hemp seeds, being the maximum value 928.1 mg/100 g, which corresponded to ‘Tiborszallasi’ variety.Potassium content was also high in hemp seeds, especially in hulled seeds, which contained on average 919.5 mg/100 g, while the average content in whole hemp seeds was 569.6 mg/100 g.Potassium ranges were wide, from 311.5 to 713.6 mg/100 g in whole hemp seeds and from 778.8 to 1067.7 mg/100 g in hulled hemp seeds.Magnesium content was also higher in hulled hemp seeds, in which ranged from 482.3 to 934.2 mg/100 g, with an average value of 696.9 mg/100 g.However, cheap grow tents the range in whole hemp seeds was very narrow and there were not statistically significant differences between the eight analysed varieties.The average magnesium content in whole hemp seeds was 383.4 mg/100 g.Calcium content, on the contrary, was higher in whole seeds, with an average value of 175.6 mg/100 g, being half in hulled hemp seeds.
In respect to microelements, most of them were more abundant in whole seeds.Iron was the major microelement in whole hemp seeds, with an average content of 8.04 mg/100 g, closely followed by zinc and manganese, whose average contents were 7.94 and 7.48 mg/100 g, respectively.Zinc was the most abundant microelement in hulled hemp seeds, with an average content of 9.81 mg/100 g.Iron content in hulled hemp seeds were slightly lower than in whole seeds, 7.83 mg/100 g, while manganese content was much lower, 5.18 mg/100 g.Copper content was lower than the other microelements, on average, 2.30 and 1.48 mg/100 g in whole and hulled hemp seeds, respectively.Among the analysed varieties, ‘Carmagnola’ variety stood out because it had the maximum values of sodium, calcium, manganese, iron, and zinc, and the minimum values of magnesium and phosphorus, and the ‘Kompolti’ variety stood out because it had the maximum values of potassium and copper, and the minimum values of calcium, manganese, and iron.Regarding hulled hemp seeds, there were a wide variation among the different brands.As it has been said previously, few studies on mineral elements in whole hemp seeds are available, so it is difficult to compare these results with previous studies.Callaway reported the contents of mineral elements of the ‘Finola’ variety, which was not analysed in this study, and Mihoc et al. studied five different Romanian varieties that were not analysed in this work either.The sodium content reported by Callaway was slightly higher, 12 mg/100 g, while all the varieties analysed in this work had sodium content lower than 5 mg/100 g , but its content was much lower than the other macroelements in both cases.That study also reported higher potassium content , closer to hulled hemp seeds than to whole seeds.Mihoc et al. obtained a wide range for this mineral element, from 569.3 to 1889.7 mg/100 g, on average.Two of those varieties had potassiumcontents within the range of this study , but the other three had much higher content.Calcium values reported by Mihoc et al. were close to those of this work , except one of the varieties, which had a content three times higher than the maximum value.The magnesium content range reported by Mihoc et al. included all the values obtained in this work, and Callaway indicated a higher value, 483 mg/100 g, but close to the maximum obtained in this work.According to Callaway , phosphorus was the most abundant mineral element, but the value was higher, 1160 mg/100 g, closer to phosphorus content in hulled hemp seeds, which were higher than 1000 mg/100 g in every sample.Iron content reported by Callaway was slightly higher than those of this work, 14 mg/100 g, but the values reported by Mihoc et al. were higher than 160 mg/100 g, 20 times the average value in whole hemp seeds.Manganese, copper, and zinc content data were consistent to those reported by Callaway and Mihoc et al..
The only literature source of mineral element content data in hulled hemp seeds is the FoodData Central.Sodium, magnesium, calcium, iron, manganese, copper, and zinc values included in the database were close to those of this work, while potassium and phosphorus values, 1200 and 1650 mg/100 g, respectively, were higher than the maximum values obtained in this work.Considering the nutrient reference values of mineral elements established by the European Union , Fig.1a represents the percentage that 100 g of whole and hulled hemp seeds contribute to those NRVs, while Fig.1b represents the contribution percentages of 30 g, which is the serving size.As it can be seen in Fig.1a, and according to European Union regulation on nutritional claims made in foods, both whole and hulled hemp seeds could be considered high in magnesium, phosphorus, manganese, copper, and zinc because their contributions were higher than 30% of NRVs.The contribution of whole hemp seeds to potassium NRV was slightly lower than 30%, so they could be considered as a source of potassium , while hulled hemp seeds could be considered, high in potassium.Whole, but not hulled hemp seeds, could be considered a source of calcium.