Estabilidade oxidativa de gérmen de milho integral autoclavado sob vapor direto e adicionado de antioxidante sintético ou natural e aplicação em biscoitos

Abstract

Corn germ has been destined, in the vast majority of cases, for animal feed, however its use in human food could add value to the co-product, if it were used as a stabilized ingredient, with the potential to generate various impacts, such as technological, economic and environmental. The objective of this research was to evaluate: the most viable conditions for roasting whole corn and degerminated corn (hominy), in order to obtain new products with a higher content of phenolic compounds and antioxidant activity for use as a natural antioxidant; the stability of flours obtained from whole corn germ treated with the application of direct steam by autoclaving without adding antioxidants, with the addition of natural antioxidant (roasted whole corn, just ground and in the form of aqueous extract) and synthetic antioxidant (BHT - butylhydroxytoluene); and also verify the feasibility of using stabilized whole corn germ to partially replace wheat flour in cookies and enrich the traditional product with fiber. The roasting of raw materials was carried out in a temperature-controlled coffee roaster. Different corn grain processing conditions were compared: T1 - hominy roasted for 10 min with final cylinder and furnace temperatures of 200 and 450 °C, respectively, T2 - hominy roasted for 10 min with final cylinder and furnace temperatures of 202 and 460 °C, respectively, T3 - whole corn grains roasted for 9 min and 10 s with final cylinder and furnace temperatures of 188 and 436 °C, respectively, T4 - whole corn grains roasted for 10 min with cylinder and furnace final temperatures of 193 and 443 °C, respectively. For stability analysis, heat-treated whole corn germ flour samples were added or not with antioxidants, packaged in vacuum metallized laminated packaging, and stored at temperatures of 20, 30 and 40 °C. The experimental samples were evaluated for their oxidative stability (TBARS), every 15 days, for 60 days. Five biscuit formulations were produced, with BC being the control (without whole corn germ) and the others with 10% (B10), 25% (B25), 40% (B40) and 55% (B55) replacement of corn flour. wheat by prepared whole corn germ flour (GMP), that is, autoclaved and added with 5% ground roasted corn. Whole corn germ is a valuable source of nutrients for human consumption, presenting a content of total dietary fiber (10.44 g 100 g-1), lipids (11.01 g 100 g-1) and available carbohydrates (57. 38 g 100 g-1), in addition to the protein content (6.83 g 100 g-1) and minerals (2.96 g 100 g-1). The fresh whole corn grains before roasting had an average CFT content of 316.29 mg 100 g-1, and average values of antioxidant activity by FRAP of 9.35 µmol FeSO4 g-1 and by DPPH of 25. 51% discoloration, while T4 (whole corn and higher degree of roasting) obtained the highest results for CFT and antioxidant activity, with an increase in relation to fresh whole corn grains of 77.22% CFT, 33.37% activity antioxidant by FRAP and 211.61% by DPPH. This indicated its potential for use as a natural antioxidant. In storage tests, when the coproduct stabilized by autoclaving under direct steam was added with roasted corn powder or roasted corn extract, lower TBARS values were determined in relation to that added with BHT or natural, indicating more promising oxidative stability results. All experimental cookies were sensorially accepted, with an acceptability index greater than 70%, with B10 standing out with the highest values for all sensorial attributes evaluated, being more accepted than BC. Aiming for greater nutritional enrichment, B25 was evaluated in relation to the proximate composition, as for both technological physical properties and sensory attributes, it did not differ statistically (p > 0.05) in relation to B10. In relation to humidity, water activity, expansion index, specific volume and hardness, there was no significant difference (p > 0.05) between the experimental cookies, but there was in relation to the instrumental color parameters, with darkening as it increased. the level of whole corn germ flour in the formulation. There was an increase of 130% in the fiber content and 22.63% in the ash content of B25 compared to BC (3.46 and 1.37%, respectively). The results obtained are important for a better understanding of the oxidative stability of corn germ, but additional studies of the proposed natural antioxidants are still necessary and to evaluate the economic viability of the processes focused on in this research, when adapted to an industrial scale. It is feasible to replace wheat flour with up to 40% of whole corn germ flour stabilized in direct autoclave steam and added 5% of ground roasted corn in cookie-type biscuits, as the biscuits have reached a standard for commercialization, being microbiologically safe and healthier than traditional biscuits, and can contribute to improving the diet and quality of life of the population, and also improve the sustainability of the corn industry. However, it is important to consider that the application of the product in bakery may require adjustments in formulations and production processes.