Effect of linoleic acid induction on the production of 1-octen-3-ol by the lipoxygenase and hydroperoxide lyase activities of Penicillium camemberti

Nutritional and microbial profiles of ripened plant-based cheese analogs collected from the European market

Plant-based cheese analogs have emerged as a novel global market trend driven by sustainability concerns for our planet. This study examines eleven soft ripened plant-based cheese analogs produced in Europe, primarily with bloomy rinds and cashew nuts as the main ingredient. First, we focused on exploring the macronutrients and salt content stated on the labels, as well a detailed fatty acid analysis of the samples. Compared to dairy cheeses, plant-based cheeses share similarities in lipid content, but their fatty acid profiles diverge significantly, with higher ratio of mono- and polyunsaturated fatty acids such as oleic and linoleic acids. We also investigated the microbiota of these analog products, employing a culture-dependent and -independent approaches. We identified a variety of microorganisms in the plant-based cheeses, with Lactococcus lactis and Leuconostoc mesenteroides being the dominant bacterial species, and Geotrichum candidum and Penicillium camemberti the dominant fungal species. Most of the species characterized are similar to those present in dairy cheeses, suggesting that they have been inoculated as culture starters to contribute to the sensorial acceptance of plant-based cheeses. However, we also identify several species that are possibly intrinsic to plant matrices or originate from the production environment, such as Pediococcus pentosaceus and Enterococcus spp. This coexistence of typical dairy-associated organisms with plant associated species highlights the potential microbial dynamics inherent in the production of plant-based cheese. These findings will contribute to a better understanding of plant-based cheese alternatives, enable the development of sustainable products, and pave the way for future research exploring the use of plant-based substrates in the production of cheese analogues.

Potential of Microorganisms to Decrease the "Beany" Off-Flavor: A Review

Vegetable proteins are in high demand due to current issues surrounding meat consumption and changes in eating habits, but they are still not accepted by consumers due to their strong bitterness, astringent taste, and "beany" off-flavor. This review aimed to give an overview of the "beany" off-flavor and the potential of microorganisms to decrease it. Twenty-six volatile compounds were identified from the literature as contributing to the "beany" off-flavor, and their formation pathways were identified in a legume matrix, pea. Biotechnological ways to improve the flavor by reducing these volatile compounds were then looked over. As aldehydes and ketones are the main type of compounds directly linked to the "beany" off-flavor, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) were focused on. By converting aldehyde and ketones into alcohols or carboxylic acids, these two enzymes have the potential to decrease the off-flavor. The presence of the two enzymes in a selection of microorganisms (Lactobacillus acidophilus, Limosilactobacillus fermentum, Lactiplantibacillus plantarum, Streptococcus thermophilus, Saccharomyces cerevisiae, and Gluconobacter suboxydans) was done with a catabolism and a bioinformatical study. Finally, the correlation between the presence of the enzyme and the efficacy to improve the flavor was investigated by comparison with the literature. The presence of ADH and/or ALDH in the strain metabolism seems linked to an odor improvement. Especially, a constitutive enzyme (ADH or ALDH) in the catabolism should give better results, showing that some fermentative types are more inclined to better the flavor. Obligatory fermentative strains, with a constitutive ADH, or acetic acid bacteria, with constitutive ADH and ALDH, show the best results and should be favored to reduce the amount of compounds involved in the "beany" off-flavor and diminish that off-flavor in legume proteins.

Selected Quality Attributes of Wheat Flour Added with Overozonized Wheat Flour

Overozonized wheat flour was added to unozonized wheat flour at three different ratios (M1: 1 : 1; M2: 1 : 2; and M3: 1 : 3), and the mixed flour was evaluated for quality properties, including pH, protein component, dough property, pasting property, and steamed bread quality. The pH of the mixed flour gradually increased as the addition content of overozonized flour decreased. The three mixed flour had higher insoluble polymeric protein (IPP) content than unozonized flour. Compared with overozonized flour, M1 and M2 flour did not show a significant difference in IPP content, but M3 flour exhibited a decreased IPP content. Three mixed flour had higher dough development time and dough stability time than both unozonized and overozonized flour, and there was no significant difference among three mixed flour in these two dough parameters. Peak, trough, and final viscosities of the three mixed flour were between those of unozonized and overozonized flour. Steamed bread of three mixed flour had larger specific volume and better texture than that of overozonized flour, with steamed bread of M3 flour showing the best attributes. Among the three mixed flour, M1 flour was the closest to overozonized flour in volatile compounds of steamed bread. These results suggested overozonized flour can be mixed with unozonized flour to decrease the deterioration of overozonization on the dough and food-making properties of wheat flour, but the mixing ratio should be taken into consideration to obtain a better quality.

Effects of pH and Cultivation Time on the Formation of Styrene and Volatile Compounds by Penicillium expansum

Styrene can be formed by the microbial metabolism of bacteria and fungi. In our previous study, styrene was determined as a spoilage marker of Fuji apples decayed by Penicillium expansum, which is responsible for postharvest diseases. In the present study, P. expansum was cultivated in potato dextrose broth added with phenylalanine—which is a precursor of styrene—using different initial pH values and cultivation times. Volatile compounds were extracted and analyzed using gas chromatography-mass spectrometry (GC-MS) combined with stir-bar sorptive extraction. The 76 detected volatile compounds included 3-methylbutan-1-ol, 3-methyl butanal, oct-1-en-3-ol, geosmin, nonanal, hexanal, and γ-decalactone. In particular, the formation of 10 volatile compounds derived from phenylalanine (including styrene and 2-phenylethanol) showed different patterns according to pH and the cultivation time. Partial least square-discriminant analysis (PLS-DA) plots indicated that the volatile compounds were affected more by pH than by the cultivation time. These results indicated that an acidic pH enhances the formation of styrene and that pH could be a critical factor in the production of styrene by P. expansum. This is the first study to analyze volatile compounds produced by P. expansum according to pH and cultivation time and to determine their effects on the formation of styrene.

1-Octanol, a self-inhibitor of spore germination in Penicillium camemberti

Penicillium camemberti is a technologically relevant fungus used to manufacture mold-ripened cheeses. This fungal species produces many volatile organic compounds (VOCs) including ammonia, methyl-ketones, alcohols and esters. Although it is now well known that VOCs can act as signaling molecules, nothing is known about their involvement in P. camemberti lifecycle. In this study, spore germination was shown to be self-regulated by quorum sensing in P. camemberti. This phenomenon, also called "crowding effect", is population-dependent (i.e. observed at high population densities). After determining the volatile nature of the compounds involved in this process, 1-octanol was identified as the main compound produced at high-spore density using GC-MS. Its inhibitory effect was confirmed in vitro and 3 mM 1-octanol totally inhibited spore germination while 100 μM only transiently inhibited spore germination. This is the first time that self-inhibition of spore germination is demonstrated in P. camemberti. The obtained results provide interesting perspectives for better control of mold-ripened cheese processes.

The relationship between exposure to microbial volatile organic compound and allergy prevalence in single-family homes

Microbial volatile organic compounds (MVOCs) are a type of VOCs produced by microorganisms. Exposure to 1-octen-3-ol, one of the known MVOCs, has been reported to reduce nasal patency and increase nasal lavage myeloperoxidase, eosinophil cationic proteins, and lysozymes in both experimental and field studies. We reported in a previous paper that 1-octen-3-ol exposure at home is associated with mucosal symptoms. In this study, our aim was to investigate the relationship between asthma and allergies and MVOC exposure in single-family homes. The subjects were 624 inhabitants of 182 detached houses in six regions of Japan. Air samples were collected using diffusive samplers, and the concentrations of eight selected MVOCs were analyzed using gas chromatography/mass spectrometry in selected-ion-monitoring mode. Each inhabitant of each of the dwellings was given a self-administered questionnaire. Among the 609 subjects who answered all of the questions about allergies, history of the medical treatment for asthma, atopic dermatitis, allergic rhinitis, and allergic conjunctivitis within the preceding two years was 4.8%, 9.9%, 18.2%, and 7.1%, respectively. A significant association between 1-octen-3-ol (per log(10) unit) and allergic rhinitis odds ratio (OR): 4.10, 95% confidence interval (CI): 1.71 to 9.80 and conjunctivitis (OR: 3.54, CI: 1.17 to 10.7) was found after adjusting for age, sex, tobacco, wall-to-wall carpeting, signs of dampness, history of treatment for hay fever, and other potentially relevant environmental factors. No relationships were found between any MVOCs and asthma or atopic dermatitis after the adjustment. The levels of MVOCs and airborne fungi were only weakly correlated. These results are consistent with previous studies that have associated higher levels of 1-octen-3-ol exposure with increased irritation of nasal and ocular mucosae. Although the indoor-air concentrations of 1-octen-3-ol found in this study were relatively low, we conclude that exposure to MVOC may be related to rhinitis and conjunctivitis.