The antimicrobial activity of linalool, citral, eugenol and thymol was determined in growth studies of both planktonic (PC) and biofilm cells (BC) Shigella flexneri. These components were evaluated either in isolation or in combinations using a sequential experimental strategy with Plackett & Burman and central composite rotational designs totaling 47 treatments. The minimum inhibitory concentration for PC was 0.125% (v v−1) for linalool and 0.5% (v v−1) for citral, eugenol and thymol. The biofilm minimum bactericidal concentration was 3 and 1% (v v−1) for linalool and citral, respectively, and 2% (v v−1) for eugenol and thymol. In the mixtures, the minimum concentrations in the efficient assays for PC growth inhibition were 0.0003, 0.0443 and 0.0443% (v v−1), for linalool, citral and thymol, respectively. In the BC, only two assays with concentrations of 0.0558, 0.0558 and 0.319% (v v−1) and 0.035, 0.035 and 0.3999% (v v−1) for linalool, citral and thymol, respectively, inhibited Shigella growth. Synergism was observed among the components, where PC and BC growth inhibition occurred at lower concentrations than those noted individually. The bactericidal effect of the components in microplate was different from the observed in stain steel coupons. Therefore, the obtained model can describe and predict the PC count of S. flexneri in medium with the tested compounds and they could be an alternative for the use in microbiological control in food industry.
In this work, a synbiotic food from hydrosoluble soy extract was developed and tested. Food products made from soymilk have frequently been rejected because of their peculiar leguminous flavor. Although lactic fermentation promotes an improvement in final flavor, Bifidobacterium produces acetic acid, which renders off flavor in the product. To improve sensory features of soymilk's synbiotic beverage, 16 flavor compounds were evaluated by preliminary affective tests using hedonic scale. The ideal sweetness and flavor were optimized using experimental design and just‐about‐right scale. Sucrose concentration presented the highest significant effect (P ≤ 0.05). Products with higher sucrose contents (9.0–11.2 g/100 mL) and 0.08–0.16 g/100 mL of flavoring presented ideal sweetness. For ideal flavor, 11 g/100 mL sucrose content or higher with any amount of flavoring was considered ideal. In conclusion, predictive models for responses with respect to the ideal flavor and sweetness, overall acceptance and purchasing attitude of a soymilk symbiotic food were obtained and validated, with highly accepted and positive purchase intent (70%) by target public.
PRACTICAL APPLICATIONS
The use of the just‐about‐right scale in sensory test is employed to measure the ideal amount of a determined compound that should be added to promote greater acceptance and preference according to the taste panel. Given that the sensory tests for the choice of the ideal are carried out in a linear manner and with one variable at a time, the present study has innovated in the application of the just‐about‐right scale, simultaneously evaluating two aspects of the ideal (sweetness and flavor) with a central composite rotatable design experimental design, and using the response surface methodology applied in the optimization of soymilk's symbiotic food. Predictive models for responses could be obtained to different sensorial optimizations in food researches.
The objective of this study was to optimize the composition of the fermentation medium through a Central Composite Rotational Design (CCRD) for the production of L (+)-latic acid (LA) using Lactobacillus rhamnosus ATCC 9595 and potato, corn steep liquor (CSL) and calcium carbonate as raw materials. A CCRD with three independent variables (potato flour (PF), CSL and CaCO 3 concentrations) was performed for a total of 17 treatments. Kinetic studies were conducted, and samples were taken at time intervals of 0 to 72 h. Cell count, pH, reducing sugars and LA concentrations were determined. LA productivity and yield, sugar consumption and cell growth factor were calculated. The highest concentration of LA was 183.8 g/L, with 2.553 g/L.h productivity, 94.2% yield and 96.1 % sugar consumption.
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