RESUMO
Oregano essential oils from Lippia berlandieri Schauer (Lb) and Poliomintha longiflora Gray (Pl) were tested against the antioxidant butylated hydroxytoluene (Bht) to evaluate effects on the shelf life of ground beef (GB) over 7 days of storage at 4°C. The treatments were GB1 = GB control, GB2 = GB +100 mg/kg of Bht, GB3 = GB +100 mg/kg of Lb, and GB4 = GB +100 mg/kg of Pl. Lightness, redness, hardness, and springiness showed differences (p < .05) between treatments and days interaction, which serve as indicators of ground beef preserved quality and consumer acceptance. Mesophilic, psychrophilic, and lactic acid bacteria numbers and antioxidant activity showed differences (p < .05) for treatments and days. Sensory attributes showed no differences between treatments. The oregano oils may provide extended shelf life for packaged meat products treated with these natural additives and hence may be used for ground beef preservation.
RESUMO
Amarantin, an 11S globulin, is one of the most important storage proteins of amaranth seeds, with relevant nutritional-functional and nutraceutical characteristics. Its cDNA was cloned in-frame with a sequence encoding a polyhistidine tag and expressed under the direction of a 35S promoter in transgenic tobacco seeds. The presence of a (His)(6) tag on the polypeptide permitted a high-yield single-step purification using immobilized metal-ion affinity chromatography and rapid characterization. Purified His-tag amarantin accounted for up to 5% of total soluble seed protein. Biochemical characterization indicated that purified His-tag amarantin migrated with the expected molecular weight (53 kDa) and was correctly processed into an acidic polypeptide (32 kDa) with isoelectric point (pI) of 5.58 and a basic polypeptide (21 kDa) with pI of 9.24, linked by a disulfide bridge. Moreover, His-tag amarantin was assembled into both homo- and hetero-hexameric 11S structures. These results show that the His tag did not change the biochemical and physicochemical properties of amarantin. The strategy presented here for rapid and high-yield expression and purification procedure should facilitate structure-function studies for this nutritional protein.