Desenvolvimento e caracterização de um isolado protéico de soja modificado com perfil de solubilidade da caseína do leite humano

• Ano de defesa: 2007
• Autor(a) principal: Silva, Mauricio Henriques Louzada
• Orientador(a): Gomes, José Carlos
• Banca de defesa: Ferreira, Karla Silva , Coimbra, Jane Sélia dos Reis
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Ciência e Tecnologia de Alimentos
• Departamento: Ciência de Alimentos; Tecnologia de Alimentos; Engenharia de Alimentos
• País: BR
• Palavras-chave em Português: Soja; Isolado protéico; Modificação; Caseina humana
• Palavras-chave em Inglês: Soybean; Protein isolate; Modification; Human casein
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::CIENCIA E TECNOLOGIA DE ALIMENTOS::CIENCIA DE ALIMENTOS
• Link de acesso: http://locus.ufv.br/handle/123456789/513

Brazil has an outstanding position as the second largest soybean producing- country worldwide. The use of soybean derivatives as functional ingredients in food has led to a better acceptance of these products by consumers. Among the processed soybean protein products, soybean protein isolate (SPI) is the most elaborate, containing high protein content. Studies have shown that technological processing alterations may alter a particular functional property. However, few studies have evaluated whether such alteration would affect protein quality. Thus, this work aimed to modify two commercial soybean protein isolates (IPSNB and IPSLH) by altering their solubility profile. A moderate acid and polyphosphate salt treatment was applied so as to present solubility curves similar to that of human casein. The degree of the modification effect on the chemical and functional properties and protein quality of these isolates was also evaluated. The modified soybean protein isolates NB and LH (IPSMNB and IPSMLH) presented, respectively, mean moisture contents (6.60% and 6.20%) significantly (p<0.05) lower compared to the commercial isolates (9.41% and 9.25%). The mean lipid content was lower than 0.5% for both SPIs. IPSMNB and IPSMLH protein content was 82.60% and 83.61%, respectively lower than those recommended by legislation (88.00%). However, the ash content of these isolates was respectively 11.15% and 11.59%, significantly (p < 0.05) higher than those of IPSNB (4.37%) and IPSLH (5.00%), justifying the lower protein values obtained for these isolates. We suggest an additional phase be added to the isolate productive process to decrease the salt content found in these studies. Mean carbohydrate content ranged from 4.18 to 5.75%, with no significant difference (p > 0.05) being found between the SPIs. The SPI mean content ranges were the following: copper, (18.22 to 20.67 mg/g) iron (90.14 mg/g to 105.49 mg/g), manganese (12.20 to 14.19 mg/g), zinc (24.91 mg/g to 32.80 mg/g), calcium (0.12 to 0.19%), magnesium (0.03 to 0.04%) and potassium (0.13 to 0.70%). Sodium contents of IPSMNB (3.31%) and IPSMLH (3.64%) were significantly (p < 0.05) higher than those of IPSNB (0.74%) and IPSLH (0.70%). The modified SPI solubility profile was similar to that of human casein in the pH range from 2.0 to 5.0. IPSNB showed significantly (p < 0.05) higher water absorption capacity than the other isolates in all the pH ranges analyzed. No significant difference (p>0.05) was found in the oil absorption capacity values between the commercial and modified isolates. The emulsifying activity varied among the treatments, especially in function of the pH. The commercial SPIs presented emulsifying stability (ES) values practically constant throughout the pH range studied. However, for the modified SPIs, a slight ES drop was observed in pH 6.0, with a marked decrease in pH values 7.0 and 8.0. Overall, modification of the commercial SPIs improved their foam formation capacity. The PER (Protein Efficiency Ratio) and RPER (Relative Protein Efficiency Ratio) mean values of the SPIs varied from 2.19 to 2.63 and from 58.22 to 69.94%, respectively, being significantly (p < 0.05) lower than those found for casein (3.77 and 100.00). The NPR (Net Protein Ratio) and RNPR (RelativeNet Protein Ratio) mean values of the treatments were significantly (p<0.05) lower than the casein standard diet (4.55 and 100.00). oscillating from 3.21 to 3.64 and 70.61 to 80.31%, respectively. No significant difference (p > 0.05) between the PER and NPR values was found between the commercial and modified SPIs. The DV values of NBSPI (94.16%), IPSMNB (93.52%) and IPSMLH (93.01%) did not differ (p > 0.05) significantly from those of casein (95.52%) and between them. However, the casein DV was significantly higher (p<0.05) than that of the IPSLH (89.44%). IPSLH modification allowed DV improvement when compared to casein. However, no difference was observed between IPSLH and IPSMLH, suggesting that there may be a relation between solubility and DV. The PDCAAS values ranged from 81 to 86%. The PDCAAS of the modified isolates are thought to be overestimated since the same amino acid content of the commercial SPI was considered. Thus, modification of commercial SPIs by combining acid treatment and polyphosphate salt caused some alterations in their chemical and functional properties while for protein quality enhancement, enhanced IPSMLH DV was observed only in relation to the casein standard diet.