Processing of whey proteins yields several bioactive peptides that can trigger physiological effects in the human body: on the nervous system via their opiate and ileum-contracting activities; on the ...cardiovascular system via their antithrombotic and antihypertensive activities; on the immune system via their antimicrobial and antiviral activities; and on the nutrition system via their digestibility and hypocholesterolemic effects. The specific physiological effects, as well the mechanisms by which they are achieved and the stabilities of the peptides obtained from various whey fractions during their gastrointestinal route, are specifically discussed in this review.
The objective of this work was to evaluate the effectiveness of antimicrobial edible coatings to wrap cheeses, throughout 60d of storage, as an alternative to commercial nonedible coatings. Coatings ...were prepared using whey protein isolate, glycerol, guar gum, sunflower oil, and Tween 20 as a base matrix, together with several combinations of antimicrobial compounds—natamycin and lactic acid, natamycin and chitooligosaccharides (COS), and natamycin, lactic acid, and COS. Application of coating on cheese decreased water loss (~10%, wt/wt), hardness, and color change; however, salt and fat contents were not significantly affected. Moreover, the antimicrobial edible coatings did not permit growth of pathogenic or contaminant microorganisms, while allowing regular growth of lactic acid bacteria throughout storage. Commercial nonedible coatings inhibited only yeasts and molds. The antimicrobial edible coating containing natamycin and lactic acid was the best in sensory terms. Because these antimicrobial coatings are manufactured from food-grade materials, they can be consumed as an integral part of cheese, which represents a competitive advantage over nonedible coatings.
The industrial exploitation of lactic acid bacteria (LAB) as starter and/or probiotic cultures depends strongly on the preservation technologies employed, which are required to guarantee long-term ...delivery of stable cultures in terms of viability and activity. Freeze-dried preparations exhibit advantages relative to preparations made with other techniques in terms of long-term preservation, coupled with convenience in handling, storage, marketing and application. Degrees of survival of LAB cultures as high as possible, during drying and subsequent storage, are thus of nuclear importance, both technologically and economically.
This review covers several factors, deemed relevant for preservation of freeze-dried LAB. The state of the art of the knowledge focussed on the improvement of LAB survival during freeze-drying and subsequent storage is presented, including specific discussion of the effects of (i) intrinsic factors, (ii) growth factors, (iii) sub-lethal treatments, (iv) drying media and (v) storage and rehydration.
Autochthonous lactic acid bacteria may provide a means of promoting the quality and safety of traditional fermented food products, in particular, artisanal cheeses. Pico cheese is an artisanal, dairy ...specialty of the Azores in risk of disappearing. Efforts to maintain its quality to the requirements of the modern markets are, thus, necessary. Lactic acid bacteria were isolated from artisanal Pico cheese, identified by sequencing of the 16S rRNA gene, and their potential as starter cultures was evaluated by studying their acidification ability, enzymatic activities (caseinolysis, lipolysis and API-ZYM profile), diacetyl and expolysaccharide production, autolysis, antimicrobial activity against Listeria monocytogenes ATCC 7466, Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29523, Pseudomonas aeruginosa ATCC 27853 and Clostridium perfringens ATCC 8357, sensory evaluation of odour formation in milk, syneresis and firmness of the curd. Several of the studied lactic acid bacteria isolates showed interesting properties for practical application as starters in artisanal cheese production. The isolates with the highest number of positive traits and, therefore, the most promising for starter development were Lactococcus lactis ssp. lactis L1C21M1, Lactobacillus paracasei L1B1E3, Leuconostoc pseudomesenteroides L1C1E6, Lactobacillus casei L1A1E5 and L1C1E8.
This review focuses on the biological properties and consequent technological roles of intestinal bacteria with potential health-promoting capacities, and provides selected examples available in the ...literature that are pertinent to the aforementioned concepts. A comprehensive overview pertaining to the taxonomy and ecology, as well as nutritional and health effects of
Bifidobacterium spp. and
Lactobacillus acidophilus, is provided; particular attention is paid to their incorporation, and growth and acidification features in fermented dairy products. The typical poor growth of these species in milk is highlighted, and the use of bifidogenic and growth factors, including their nature and function, is discussed. Efforts to establish optimum environmental conditions for their growth are critically reviewed, in addition to the effects of the food and storage conditions on microbial survival. Criteria for selection of effective microbial strains for their probiotic effect are listed, and modifications to improve fermentation efficiency and shelf-life of final dairy products are suggested; among these, the incorporation of
Bifidobacterium spp. and
L. acidophilus into a solid matrix, such as cheese, is emphasized.
Palladium-based fiber-optic sensors have been one of the most promising configurations for hydrogen sensing. In the latest decade, fiber-optic sensors have indeed earned a strong interest owing to ...their ability to monitor molecular hydrogen at specific spatial points-either as a sensing tip device or in large areas via multiple sensing regions distributed along the optical fiber. This review focuses on the various types of optical fiber hydrogen sensors, containing specifically palladium as active element. Three distinct working principles are described, viz. interferometric-, in tensity-, and fiber grating-based sensors; their characteristics and sensing performances are critically overviewed.
The potential angiotensin-converting enzyme (ACE)–inhibitory and antioxidant activities of peptides in water-soluble extracts, obtained from raw and sterilized ovine and caprine cheeselike systems ...coagulated with enzymes from the plant Cynara cardunculus, were assessed. Prior to the assay, the 3,000-Da permeate from 45-d-old cheeselike systems was fractionated by tandem chromatographic techniques. Several peaks were obtained in each chromatogram, but only some were associated with ACE-inhibitory or antioxidant activity or both. Peptides Tyr-Gln-Glu-Pro, Val-Pro-Lys-Val-Lys, and Tyr-Gln-Glu-Pro-Val-Leu-Gly-Pro-* from β-casein, as well as Arg-Pro-Lys and Arg-Pro-Lys-His-Pro-Ile-Lys-His-* from αs1-casein exhibited ACE-inhibitory activity. Peptides released upon cleavage of the peptide bond Leu190-Tyr191 (either in ovine or caprine β-casein), and corresponding to the β-casein sequence Tyr-Gln-Glu-Pro-*, possessed antioxidant activity.
The survival rates of
Lactobacilus acidophilus Ki,
Lactobacillus paracasei L26 and
Bifidobacterium animalis BB-12 were studied after whey protein microencapsulation via spray-drying, with or without
...l-cysteine-HCl, and storage up to 6 months at 5 °C and 22 °C, with variation in relative air humidity and oxygen levels.
Lb. paracasei L26 was the least susceptible to storage conditions: above 10
6 cfu g
−1 were recorded by 180 d at 22 °C, irrespective of relative humidity, and the presence/absence of oxygen and
l-cysteine. Higher relative humidity, higher temperature and longer storage periods were deleterious to survival of both
B. animalis BB-12 and
Lb. acidophilus Ki; the effect of
l-cysteine-HCl was dependent on the probiotic strain. The effect of overhead oxygen was not significant upon any probiotic strain studied. Whey protein microcapsules containing
l-cysteine-HCl protected probiotic cultures from simulated gastrointestinal conditions.
Aims: To investigate the influence of yeast extract, peptone, temperature and pH upon protease productivity by Bacillus sp. HTS102 – a novel wild strain isolated from wool of a Portuguese sheep breed ...(Merino). Methods and Results: A 24 full factorial, central composite design together with response surface methodology was used to carry out the experiments and analyse the results, respectively. Among the individual parameters tested, temperature and peptone concentration produced significant effects upon protease productivity. A high correlation coefficient (R2 = 0·994, P < 0·01) indicated that the empiric second‐order polynomial model postulated was adequate to predict said productivity, with the optimum loci characterized by: temperature of 43°C, peptone content of 1·4 g l−1, pH of 5·1 and yeast extract concentration of 10·0 g l−1. Conclusions: Protease synthesis depends chiefly on temperature and peptone level. The maximum protease activity was more than twice that obtained with the basal medium, so the experimental design and analysis undertaken were effective towards process optimization. Significance and Impact of the Study: Rational choice of processing conditions for maximum protease productivity will be relevant if an economically feasible fermentation process based on Bacillus sp. HTS102 is intended.
Background: High levels of viable Staphylococcus aureus, which are often found on inflamed skin surfaces, are usually associated with atopic dermatitis. Textiles, owing to their high specific surface ...area and intrinsic hydrophilicity, retain moisture while also providing excellent environmental conditions for microbial growth and proliferation. Recently, a number of chemicals have been added to textiles, so as to confer antimicrobial activity. Aims: To evaluate the antimicrobial action of chitosan upon selected skin staphylococci. Methods and Results: We isolated staphylococci from normal skin of 24 volunteers and studied their survival upon contact with chitosan‐impregnated cotton fabric. Low and high molecular weight chitosans were used at two concentrations; all four did effectively reduce the growth of some staphylococci (namely Staph. aureus), by up to 5 log cycles, thus unfolding a potential towards control and even prevention of related skin disorders. Conclusion: Our data suggest an effective, but selective antibacterial action of chitosans towards skin bacteria. Significance and Impact of the Study: The possibility to use a natural biopolymer incorporated in a textile to alleviate and even treat some of the symptoms associated with this skin condition may raise an alternative to existing medical treatments. The selectivity observed prevents full elimination of bacteria from the skin surface, which is an advantage.
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