Main Article Content
Lemna minor (L. minor), the common duckweed, contains a high protein substance and is considered as a good source of potential bioactive peptides. The objective of this study is to investigate the effect of enzymatic hydrolysis times (60–180 min) and enzyme concentrations (0.5–3.5%v/w) with Alcalase and Flavourzyme on the recovery, hydrolysis degree (DH), and antioxidant properties of peptides derived from defatted L. minor. The protein recovery, hydrolysis degree (DH), and antioxidant activities obtained by enzymatic were compared with the alkaline treatment method. The results showed that the protein recovery, DH values, and antioxidant activities were enhanced by increasing the enzyme concentration and hydrolysis time. Specifically, the recovery of protein and DH values reached the highest level after the enzymatic hydrolysis by Flavourzyme or Alcalase at 1.5 v/w enzyme for 120 min. At the same enzymatic hydrolysis condition, the samples hydrolyzed by Flavourzyme had a higher inhibitory effect on the ABTS•+ and DPPH•+ radical scavenging than those hydrolyzed by Alcalase and the alkaline treatment. Further study also showed that the DH values, amino acid contents, and antioxidant activities of the protein extracts were positively correlated. Thus, the extractions with Flavourzyme and Alcalse were a good method to produce a significant amount of amino acids and smaller peptides.
 K. J. Appenroth, K. S. Sree, V. Böhm, S. Hammann, W. Vetter, M. Leiterer, and G. Jahreis, “Nutritional value of duckweeds (Lemnaceae) as human food,” Food Chemistry, vol. 217, pp. 266–273, 2017, doi: 10.1016/j.foodchem.2016.08.116.
 R. Chakrabarti, W. D. Clark, J. G. Sharma, R. K. Goswami, A. K. Shrivastav, and D. R. Tocher, “Mass production of Lemna minor and its amino acid and fatty acid profiles,” Frontiers in Chemistry, vol. 6, pp. 1–16, 2018, doi: 10.3389/ fchem.2018.00479.
 L. L. Rusoff, E. W. Blakeney, and D. D. Culley, “Duckweeds (Lemnaceae family): A potential source of protein and amino acids,” Journal of Agricultural and Food Chemistry, vol. 28, no. 4, pp. 848–850, 1980, doi: 10.1021/jf60230a040.
 W. Maciejewska-Potapczyk, L. Konopska, and K. Olechnowicz, “Protein in Lemna minor L.,” Biochemie und Physiologie der Pflanzen, vol. 167, no. 1, pp. 105–108, 1975, doi: 10.1016/s0015- 3796(17)30757-6.
 M. F. A. de Beukelaar, G. G. Zeinstra, J. J. Mes, and A. R. H. Fischer, “Duckweed as human food. The influence of meal context and information on duckweed acceptability of Dutch consumers,” Food Quality and Preference, vol. 71, 2018, pp. 76– 86, 2019, doi: 10.1016/j.foodqual.2018.06.005.
 E. D’Hondt, J. Martín-uárez, S. Bolado, J. Kasperoviciene, J. Koreiviene, S. Sulcius, K. Elst, and L.Bastiaens, “Cell disruption technologies,” Microalgae-Based Biofuels and Bioproducts, pp. 133–154, 2017, doi: 10.1016/B978-0-08-1010 23-5.00006-6.
 R. Chirinos, M. Aquino, R. Pedreschi, and D. Campos, “Optimized methodology for alkaline and enzyme-assisted extraction of protein from Sacha Inchi (Plukenetia volubilis) kernel cake,” Journal of Food Process Engineering, vol. 40, no. 2, 2017, doi: 10.1111/jfpe.12412.
 Y. W. Sari, W. J. Mulder, J. P. M. Sanders, and M. E. Bruins, “Towards plant protein refinery: Review on protein extraction using alkali and potential enzymatic assistance,” Biotechnology Journal, vol. 10, no. 8, pp. 1138–1157, 2015, doi: 10.1002/biot.201400569.
 V. Vásquez, R. Martínez, and C. Bernal, “Enzymeassisted extraction of proteins from the seaweeds Macrocystis pyrifera and Chondracanthus chamissoi: Characterization of the extracts and their bioactive potential,” Journal of Applied Phycology, vol. 31, no. 3, pp. 1999–2010, 2019, doi: 10.1007/s10811-018-1712-y.
 J. A. do Evangelho, J. de J. Berrios, V. Z. Pinto, M. D. Antunes, N. L. Vanier, and E. da R. Zavareze, “Antioxidant activity of black bean (Phaseolus vulgaris L.) protein hydrolysates,” Food Science and Technology, vol. 36, pp. 23–27, 2016, doi: 10.1590/1678-457X.0047.
 N. Ahmadifard, J. H. C. Murueta, A. Abedian-Kenari, A. Motamedzadegan, and H. Jamali, “Comparison the effect of three commercial enzymes for enzymatic hydrolysis of two substrates (rice bran protein concentrate and soy-been protein) with SDS-PAGE,” Journal of Food Science and Technology, vol. 53, no. 2, pp. 1279–1284, 2016, doi: 10.1007/s13197-015-2087-6.
 L. You, M. Zhao, C. Cui, H. Zhao, and B. Yang, “Effect of degree of hydrolysis on the antioxidant activity of loach (Misgurnus anguillicaudatus) protein hydrolysates,” Innovative Food Science and Emerging Technologies, vol. 10, no. 2, pp. 235–240, 2009, doi: 10.1016/j.ifset.2008.08.007.
 M. F. Sbroggio, M. S. Montilha, V. R. G. de Figueiredo, S. R. Georgetti, and L. E. Kurozawa, “Influence of the degree of hydrolysis and type of enzyme on antioxidant activity of okara protein hydrolysates,” Food Science and Technology, vol. 36, no. 2, pp. 375–381, 2016, doi: 10.1590/ 1678-457X.000216.
 C. M. Verdasco-Martín, L. Echevarrieta, and C. Otero, “Advantageous preparation of digested proteic extracts from Spirulina platensis biomass,” Catalysts, vol. 9, no. 2, 2019, doi: 10.3390/catal9020145.
 M. R. Segura-Campos, L. Espinosa-García, L. A. Chel-Guerrero, and D. A. Betancur-Ancona, “Effect of enzymatic hydrolysis on solubility, hydrophobicity, and in vivo digestibility in cowpea (Vigna unguiculata),” International Journal of Food Properties, vol. 15, no. 4, pp. 770–780, 2012, doi: 10.1080/10942912.2010.501469.
 Y. Zhang, H. Zhang, L. Wang, X. Guo, X. Qi, and H. Qian, “Influence of the degree of hydrolysis (DH) on antioxidant properties and radicalscavenging activities of peanut peptides prepared from fermented peanut meal,” European Food Research and Technology, vol. 232, no. 6, pp. 941– 950, 2011, doi: 10.1007/s00217-011-1466-0.
 Z. Shahi, S. Z. Sayyed-Alangi, and L. Najafian, “Effects of enzyme type and process time on hydrolysis degree, electrophoresis bands and antioxidant properties of hydrolyzed proteins derived from defatted Bunium persicum Bioss. press cake,” Heliyon, vol. 6, no. 2, 2020, doi: 10.1016/j.heliyon.2020.e03365.
 S. Feyzi, M. Varidi, F. Zare, and M. J. Varidi, “Fenugreek (Trigonella foenum graecum) seed protein isolate: Extraction optimization, amino acid composition, thermo and functional properties,” Journal of the Science of Food and Agriculture, vol. 95, no. 15, pp. 3165–3176, 2015, doi: 10.1002/jsfa.7056.
 AOAC, Official Method 942.05 - Ash. Maryland: AOAC Official Methods of Analysis, 2000, pp. 5–15.
 V. M. Phan, T. Junyusen, P. Liplap, and P. Junyusen, “Effects of ultrasonication and thermal cooking pretreatments on the extractability and quality of cold press extracted rice bran oil,” Journal of Food Process Engineering, vol. 42, no. 2, pp. 1–8, 2018, doi: 10.1111/jfpe.12975.
 E. Barbarino and S. O. Lourenço, “An evaluation of methods for extraction and quantification of protein from marine macro- and microalgae,” Journal of Applied Phycology, vol. 17, no. 5, pp. 447–460, 2005, doi: 10.1007/s10811-005- 1641-4.
 X. Zhang, P. Noisa, and J. Yongsawatdigul, “Chemical and cellular antioxidant activities of in vitro digesta of tilapia protein and its hydrolysates,” Foods, vol. 9, no. 6, 2020, doi: 10.3390/foods9060833.
 M. Garcia-Vaquero, M. Lopez-Alonso, and M. Hayes, “Assessment of the functional properties of protein extracted from the brown seaweed Himanthalia elongata (Linnaeus) S. F. Gray,” Food Research International, vol. 99, pp. 971– 978, 2017, doi: 10.1016/j.foodres.2016.06.023.
 H. A. Nchienzia, R. O. Morawicki, and V. P. Gadang, “Enzymatic hydrolysis of poultry meal with endo- and exopeptidases,” Poultry Science, vol. 89, no. 10, pp. 2273–2280, 2010, doi: 10.3382/ps.2008-00558.
 Y. Hou, J. Zhou, W. Liu, Y. Cheng, L. Wu, and G. Yang, “Preparation and characterization of antioxidant peptides from fermented goat placenta,” Food Science of Animal Resources, vol. 34, no. 6, pp. 769–776, 2014, doi: 10.5851/ kosfa.2014.34.6.769.
 F. Bamdad, J. Wu, and L. Chen, “Effects of enzymatic hydrolysis on molecular structure and antioxidant activity of barley hordein,” Journal of Cereal Science, vol. 54, no. 1, pp. 20–28, 2011, doi: 10.1016/j.jcs.2011.01.006.
 M. Karamać, A. Kosińska-Cagnazzo, and A. Kulczyk, “Use of different proteases to obtain flaxseed protein hydrolysates with antioxidant activity,” International Journal of Molecular Sciences, vol. 17, no. 7, 2016, doi: 10.3390/ ijms17071027.
 R. J. Elias, S. S. Kellerby, and E. A. Decker, “Antioxidant activity of proteins and peptides,” Critical Reviews in Food Science and Nutrition, vol. 48, no. 5, pp. 430–441, 2008, doi: 10.1080/ 10408390701425615.
 J. Y. Je, P. J. Park, and S. K. Kim, “Antioxidant activity of a peptide isolated from Alaska pollack (Theragra chalcogramma) frame protein hydrolysate,” Food Research International, vol. 38, no. 1, pp. 45–50, 2005, doi: 10.1016/j. foodres.2004.07.005.