Flax and hemp contain significant quantities of high quality oil in their seeds (rich in omega-3 and omega-6). These essential fatty acids have been shown to reduce inflammation and help prevent some chronic disease (hearh disease and arthritis). As a consequence of this, there is an increasing demand of these healthy oils by food industry. Oil extraction makes available flours which can be considered new sources of protein and fiber. In this study, we evaluate six varieties of each specie (flax and hemp) to characterize the protein component of the seeds. To do this we set up experimental field trials for two consecutive years (2011-2012) in Italy in two different locations of Lombardy region: Treviglio and Cavriana. All the analyses were carried out on the remaining meal after chemical extraction of oil. The protein content in the six genotypes of flaxseed meal (FSM) was, on average 360 g kg-1 dry matter (DM). There were not differences between site and year of cultivation except genotype Valoal. It showed a protein content higher in 2011 (about 360 g kg-1 DM) respect to 2012 (about 340 g kg-1 DM) in both experimental fields. The protein content in hempseed meal (HSM) was, on average 340 g kg-1 DM. Substantial differences were evident between years of cultivation. In 2012, protein concentration was higher (360 g kg-1) respect to first year (340 g kg-1) for all hemp varieties and in the two experimental fields. Amino acid (AA) profile was obtained of the hydrolyzed protein of six genotypes of flax and hemp. The AA content was determined on hydrolyzed protein by HPLC analysis. Flax showed a good content of threonine and histidine (4.7 and 6.0 g 100 g-1protein, respectively) which was higher respect to hemp (3.3 and 2.9 g 100 g-1 protein, respectively). Plant storage proteins are often poor in lysine (cereals) or sulfurated AA (legumes). Hemp protein showed a discrete quantity of lysine (4.2 g 100 g-1 protein) that resulted higher respect to flax (2.8 g 100 g-1 protein) but lower than soybean (6.0 g 100 g-1 protein). Instead, methionine content of flax and hemp (2.6 and 2.4 g 100 g-1 protein, respectively) proteins were significantly higher respect to soybean (1.2 g 100 g-1 protein). Moreover, flax and hemp proteins were extremely rich in arginine (8.0 and 12.0 g 100 g-1 protein, respectively). This is interesting since young mammals have a high dietary requirement for arginine due to its role as a nitrogen carrier in tissue proteins and its key role in gastrointestinal growth and development. We also monitored the presence of some antinutritional compounds in flours as they can reduce the protein digestibility. The concentration of condensed tannins, trypsin inhibitors, and saponins were to acceptable levels. Instead, phytic acid deserve attention being about 5% and 7% dry weight in FSM and HSM, respectively. In conclusion, FSM and HSM could be new rich protein sources with an interesting AA profile rich in arginine and with a good content of sulfurated AA.
Protein concentration and amino acid profile in hempseed and flaxseed meal
Remo Reggiani
2015
Abstract
Flax and hemp contain significant quantities of high quality oil in their seeds (rich in omega-3 and omega-6). These essential fatty acids have been shown to reduce inflammation and help prevent some chronic disease (hearh disease and arthritis). As a consequence of this, there is an increasing demand of these healthy oils by food industry. Oil extraction makes available flours which can be considered new sources of protein and fiber. In this study, we evaluate six varieties of each specie (flax and hemp) to characterize the protein component of the seeds. To do this we set up experimental field trials for two consecutive years (2011-2012) in Italy in two different locations of Lombardy region: Treviglio and Cavriana. All the analyses were carried out on the remaining meal after chemical extraction of oil. The protein content in the six genotypes of flaxseed meal (FSM) was, on average 360 g kg-1 dry matter (DM). There were not differences between site and year of cultivation except genotype Valoal. It showed a protein content higher in 2011 (about 360 g kg-1 DM) respect to 2012 (about 340 g kg-1 DM) in both experimental fields. The protein content in hempseed meal (HSM) was, on average 340 g kg-1 DM. Substantial differences were evident between years of cultivation. In 2012, protein concentration was higher (360 g kg-1) respect to first year (340 g kg-1) for all hemp varieties and in the two experimental fields. Amino acid (AA) profile was obtained of the hydrolyzed protein of six genotypes of flax and hemp. The AA content was determined on hydrolyzed protein by HPLC analysis. Flax showed a good content of threonine and histidine (4.7 and 6.0 g 100 g-1protein, respectively) which was higher respect to hemp (3.3 and 2.9 g 100 g-1 protein, respectively). Plant storage proteins are often poor in lysine (cereals) or sulfurated AA (legumes). Hemp protein showed a discrete quantity of lysine (4.2 g 100 g-1 protein) that resulted higher respect to flax (2.8 g 100 g-1 protein) but lower than soybean (6.0 g 100 g-1 protein). Instead, methionine content of flax and hemp (2.6 and 2.4 g 100 g-1 protein, respectively) proteins were significantly higher respect to soybean (1.2 g 100 g-1 protein). Moreover, flax and hemp proteins were extremely rich in arginine (8.0 and 12.0 g 100 g-1 protein, respectively). This is interesting since young mammals have a high dietary requirement for arginine due to its role as a nitrogen carrier in tissue proteins and its key role in gastrointestinal growth and development. We also monitored the presence of some antinutritional compounds in flours as they can reduce the protein digestibility. The concentration of condensed tannins, trypsin inhibitors, and saponins were to acceptable levels. Instead, phytic acid deserve attention being about 5% and 7% dry weight in FSM and HSM, respectively. In conclusion, FSM and HSM could be new rich protein sources with an interesting AA profile rich in arginine and with a good content of sulfurated AA.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.