Long-Term Fungal Inhibition by Pisum sativum Flour Hydrolysate during Storage of Wheat Flour Bread

Abstract

In order to identify antifungal compounds from natural sources to be used as ingredients in the bakery industry, water/salt-soluble extracts (WSE) from different legume flour hydrolysates obtained by the use of a fungal protease were assayed against Penicillium roqueforti DPPMAF1. The agar diffusion assays allowed the selection of the pea (Pisum sativum) hydrolysate as the most active. As shown by the hyphal radial growth rate, the WSE had inhibitory activity towards several fungi isolated from bakeries. The MIC of the WSE was 9.0 mg/ml. Fungal inhibition was slightly affected by heating and variations in pH. The antifungal activity was attributed to three native proteins (pea defensins 1 and 2 and a nonspecific lipid transfer protein [nsLTP]) and a mixture of peptides released during hydrolysis. The three proteins have been reported previously as components of the defense system of the plant. Five peptides were purified from WSE and were identified as sequences encrypted in leginsulin A, vicilin, provicilin, and the nsLTP. To confirm antifungal activity, the peptides were chemically synthesized and tested. Freeze-dried WSE were used as ingredients in leavened baked goods. In particular, breads made by the addition of 1.6% (wt/wt) of the extract and fermented by baker's yeast or sourdough were characterized for their main chemical, structural, and sensory features, packed in polyethylene bags, stored at room temperature, and compared to controls prepared without pea hydrolysate. Artificially inoculated slices of a bread containing the WSE did not show contamination by fungi until at least 21 days of storage and behaved like the bread prepared with calcium propionate (0.3%, wt/wt). Contamination by fungi is the most common cause of microbial spoilage and a costly problem for bakeries. In many cases, it is the major factor governing shelf life. In addition to the repellent sight of visible growth, fungi may be responsible for off-flavors and may synthesize mycotoxins and allergenic compounds (1, 2).Chemical preservatives, novel ingredients with fungus-inhibiting properties, and packaging techniques are all technology options that, together with hygiene during processing, may contribute to decreasing the growth of fungi in baked goods (3). Routinely, salts of propionic, sorbic, and benzoic acids, as well as ethanol, are used as chemical preservatives. Nevertheless, consumers require high-quality, preservative-free, safe but mildly processed foods with extended shelf life and preserved sensory properties. These requirements have led to a search for new preservatives derived mainly from natural sources. In nature, antifungal compounds from plants comprise proteins and peptides that are thought to play an important role in plant disease resistance, serving as protective agents against fungal invasion (4). In particular, leguminous plants represent an important reservoir to be investigated owing to their abundance of proteins with important biological activities (5). Overall, leguminous proteins are classified as prote...

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A novel lipid transfer protein from the pea Pisum sativum: isolation, recombinant expression, solution structure, antifungal activity, lipid binding, and allergenic properties

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Soybean β‐conglycinin and catfish cutaneous mucous p22 glycoproteins deteriorate sporangial cell walls of Pseudoperonospora cubensis and suppress cucumber downy mildew

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