Inhibition of Aspergillus carbonarius growth and Ochratoxin A production using lactic acid bacteria cultivated in an optimized medium.

The Gram-positive bacteria lactic acid bacteria (LAB) are used in the food industry but are also known for inhibiting certain food spoilage microorganisms, especially fungi. Sources of nitrogen (N) for culture media are generally organic and expensive. Many attempts have been made to formulate economical culture media with alternative N sources obtained from agricultural and industrial byproducts. This study describes the design and optimization of an inexpensive culture medium for Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) MZ809351 strain B31. The culture medium was optimized using statistical experimental designs to identify the factors with the most significant effects on biomass concentration to reduce the overall cost, aiming to obtain a biomass concentration similar to that obtained with the reference LAB culture medium (de Man, Rogosa and Sharpe; MRS). Sodium acetate and magnesium sulfate were the most significant factors (p < 0.005), and their contents were reduced by 22 % and 40 %, respectively, without affecting biomass concentration. Malt germ extract (MGE) was used as an alternative nitrogen source to replace meat extract (ME) and proteose peptone (PP). Through these experiments, the composition of a culture medium that is less expensive than MRS broth was defined, which produced a biomass concentration (3.8 g/L) similar to that obtained with MRS medium. The inhibitory effects of two LAB strains isolated from the Ivory Coast and Mexico on the growth and production of ochratoxin A (OTA) in an ochratoxigenic fungus was tested. The minimum cellular concentration of the LAB to prevent the development of Aspergillus carbonarius Ac 089 and the production of OTA was determined in a model assay in Petri dishes. The conditions to inhibit the germination of A. carbonarius Ac 089 and the production of OTA were found. Using the optimized medium and a ratio of 2 × 104 LAB/spore (1 × 108 CFU/mL) strain B7 (L. plantarum MZ809351) and 2 × 103 LAB/spore (1 × 107 CFU/mL) strain B31 (L. plantarum MN922335) completely inhibited the growth of the fungus. A ratio of 2 × 105 LAB/spore (1 × 109 CFU/mL) was required to inhibit OTA production with strains B7 and B31. This study indicates the potential of cultivating LAB in an optimized and inexpensive culture medium for use as a biological control agent against ochratoxigenic fungi in food.

Effects of CaCO3 treatment on the morphology, crystallinity, rheology and hydrolysis of gelatinized maize starch dispersions.

Using calcium salts instead of lime allows for an ecological nixtamalization of maize grains, where the negative contamination impact of the traditional lime nixtamalization is reduced. This work assessed the effects of calcium carbonate (0.0-2.0%w/w CaCO3) on the morphology, crystallinity, rheology and hydrolysis of gelatinized maize starch dispersions (GMSD). Microscopy analysis showed that CaCO3 changed the morphology of insoluble remnants (ghosts) and decreased the degree of syneresis. Analysis of particle size distribution showed a slight shift to smaller sizes as the CaCO3 was increased. Also, X-ray patterns indicated that crystallinity achieved a minimum value at CaCO3 concentration in the range of 1%w/w. GMSD with higher CaCO3 concentrations exhibited higher thixotropy area and complex viscoelastic behavior that was frequency dependent. A possible mechanism involved in the starch chain modification by CaCO3 is that starch may act as a weak acid ion exchanger capable of exchanging alcoholic group protons for cations (Ca(+2)).

Angiotensin I-Converting Enzyme inhibitory and antioxidant activities and surfactant properties of protein hydrolysates as obtained of Amaranthus hypochondriacus L. grain.

Even though some research has been carried out on surfactant properties of amaranth protein hydrolysates, their bio-functionality has not been studied yet. In this work amaranth grain Alb 1 and Glob were hydrolyzed (Alb 1H, Glob H) and foams and emulsions at optimal conditions (t, E/S, pH5) were prepared in order to assess techno-functional properties such as foaming (F) and emulsifying (E) (capacity (C) and stability (S)). FC and EC were much better for Glob H than for Alb H. Angiotensin I-converting enzyme-inhibitory activity was higher for Alb 1H (roughly 50 %) than that of Glob H (roughly 30 %). Scavenging of radicals activity (DPPH· or ABTS· (+) ) of Alb 1H and Glob H, at 2 mg/mL, was similar (approx. 40 %), but lower than Alb 1 (approx. 70 %), which was the best antioxidant. The low reducing power showed that hydrolysates barely donate an electron or hydrogen. Chelating activity on Cu(2+) was lower than that exhibited by Fe(2+,) which was remarkable, approx. 80 % as long as DH% > 10 %, where hydrolysates displayed high solubility (Alb 1H = 85 %, Glob H = 70 %) because of occurrence of 1-10 kDa peptides. Amaranth foams and emulsions prepared with protein hydrolysates have a potential as a nutraceutical food.

Effect of fermentation time and drying temperature on volatile compounds in cocoa.

The effects of fermentation time and drying temperature on the profile of volatile compounds were evaluated after 2, 4, 6, and 8 fermentation days followed by drying at 60, 70 and 80°C. These treatments were compared with dry cocoa controls produced in a Samoa drier and by a sun-drying process. A total of 58 volatile compounds were identified by SPME-HS/GC-MS and classified as: esters (20), alcohols (12), acids (11), aldehydes and ketones (8), pyrazines (4) and other compounds (3). Six days of fermentation were enough to produce volatile compounds with flavour notes desirable in cocoa beans, as well as to avoid the production of compounds with off-flavour notes. Drying at 70 and 80°C after six fermentation days presented a volatile profile similar to the one obtained by sun drying. However, drying at 70°C represents a lower cost. Given the above results, in the present study the optimal conditions for fermentation and drying of cocoa beans were 6days of fermentation, followed by drying at 70°C.