Modifications of the volatile and nonvolatile metabolome of goat cheese due to adjunct of non-starter lactic acid bacteria

Aloe arborescens supplementation in drying-off dairy cows: influence on rumen, rectum and milk microbiomes

BACKGROUND

In the context of the RABOLA project, which aimed to identify operational practices that lead to the reduction of antibiotic use in dairy cattle farming, lyophilised Aloe arborescens was administered orally to cows during the dry-off and peripartum periods. In this specific paper we wanted to examine whether oral administration of Aloe arborescens, in combination with the topical application of a teat sealant could exert an effect on the microbial populations of three cow microbiomes (rumen, milk, rectum), between dry-off and peripartum. Dry-off and peripartum are critical physiological phases of the cow's life, where both the mammary gland and the gastrointestinal tract undergo dramatic modifications, hence the relevance of evaluating the effects of dietary treatments.

METHODS

Thirty multiparous dairy cows were randomly allocated to three groups: Control (antibiotic treatment and internal teat sealant), Sealant (only internal teat sealant) and Aloe (internal teat sealant and Aloe arborescens homogenate administered orally). For 16S rRNA gene sequencing, rumen, rectum and milk samples were collected, not synchronously, at the most critical timepoints around dry-off and calving, considering the physiological activity of each biological site.

RESULTS

The rumen microbiome was predominantly characterized by Bacteroidetes and Firmicutes followed by Proteobacteria, while the rectum exhibited a prevalence of Firmicutes and Bacteroidetes. The milk microbiome mainly comprised Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. Alistipes spp., Ruminococcaceae UCG-10 group, Prevotellaceae UCG-001 group, and Bacteroides spp., involved in cellulose and hemicellulose degradation, enhancement of energy metabolism, and peptide breakdown, showed increment in the rectum microbiome with Aloe supplementation. The rectum microbiome in the Aloe group exhibited a significant increase in the Firmicutes to Bacteroidetes ratio and alpha-diversity at seven days after dry-off period. Beta-diversity showed a significant separation between treatments for the rectum and milk microbiomes. Aloe supplementation seemed to enrich milk microbial composition, whereas the Sealant group showed greater diversity compared to the Control group, albeit this included an increase in microorganisms frequently associated with mastitis.

CONCLUSIONS

Aloe arborescens administration during the dry-off period did not demonstrate any observable impact on the microbial composition of the rumen, a finding further supported by volatilome analysis. Instead, the oral Aloe supplementation at dry-off appears to significantly influence the composition of the dairy cow rectum and milk microbiomes in the following lactation.

Insect live larvae as a new nutritional model in duck: effects on gut health

BACKGROUND

This study aimed to evaluate the effects of Hermetia illucens (Black soldier fly-BSF) and Tenebrio molitor (Yellow mealworm-YMW) live larvae as a new nutritional model on duck's gut health, considering gut histomorphometry, mucin composition, cytokines transcription levels, and microbiota. A total of 126, 3-days-old, females Muscovy ducks were randomly allotted to three dietary treatments (6 replicates/treatment, 7 birds/pen): (i) C: basal diet; (ii) BSF: C + BSF live larvae; (iii) YMW: C + YMW live larvae. BSF and YMW live larvae were administered on top of the basal diet, based on the 5% of the expected daily feed intake. The live weight, average daily gain, average daily feed intake and feed conversion ratio were evaluated for the whole experimental period. On day 52, 12 ducks/treatment (2 birds/replicate) were slaughtered and samples of duodenum, jejunum, ileum, spleen, liver, thymus and bursa of Fabricius were collected for histomorphometry. Mucin composition was evaluated in the small intestine through histochemical staining while jejunal MUC-2 and cytokines transcription levels were evaluated by rt-qPCR. Cecal microbiota was also analyzed by means of 16 S rRNA gene sequencing.

RESULTS

Birds' growth performance and histomorphometry were not influenced by diet, with a proximo-distal decreasing gradient from duodenum to ileum (p < 0.001), respecting the physiological gut development. Mucin staining intensity and MUC-2 gene expression did not vary among dietary treatments, even though mucin intensity increased from duodenum to ileum, according to normal gut mucus physiology (p < 0.001). Regarding local immune response, IL-6 was higher in YMW group when compared to the other groups (p = 0.009). Insect live larvae did not affect cecal microbiota diversity, but BSF and YMW groups showed a higher presence of Helicobacter, Elusimicrobium, and Succinatimonas and a lower abundance of Coriobacteriaceae and Phascolarctobacterium compared to C birds (p < 0.05).

CONCLUSIONS

The use of BSF and YMW live larvae as new nutritional model did not impair gut development and mucin composition of Muscovy ducks, but slightly improved the intestinal immune status and the microbiota composition by enhancing regulatory cytokine IL-6 and by increasing minor Operational Taxonomic Units (OTUs) involved in short-chain fatty acids production.

Metabolites, flavor profiles and ripening characteristics of Monascus-ripened cheese enhanced by Ligilactobacillus salivarius AR809 as adjunct culture

Adjunct cultures strongly determined the distinguishing sensorial and nutritional characteristics of cheeses. Metabolites, flavor profiles and ripening characteristics of Monascus-ripened cheese enhanced by the co-fermentation of Ligilactobacillus salivarius AR809 were investigated. The AR809 significantly increased the contents of soluble nitrogen, small peptides (<1200 Da), free amino acids, and casein degradation degree in the resulting cheese. Furthermore, AR809 significantly promoted the formation of methyl ketones during cheese maturation. Based on untargeted metabolomics analysis, metabolites related to fatty acids metabolism and lysine degradation were highly enriched in Monascus-rich region of cheese. AR809 was primarily engaged in amino acid metabolism, promoting the synthesis of amino acids and dipeptide. L. salivarius and Monascus co-fermentation produced more beneficial bioactive metabolites involved in amino acids and lipid metabolisms than Monascus used alone in cheese ripening. Therefore, as adjunct culture, L. salivarius AR809 exhibited tremendous potential in improving nutrition and flavor quality during cheese ripening.

Potential of Cheese-Associated Lactic Acid Bacteria to Metabolize Citrate and Produce Organic Acids and Acetoin

Lactic acid bacteria (LAB) are pivotal in shaping the technological, sensory, and safety aspects of dairy products. The evaluation of proteolytic activity, citrate utilization, milk pH reduction, and the production of organic compounds, acetoin, and diacetyl by cheese associated LAB strains was carried out, followed by Principal Component Analysis (PCA). Citrate utilization was observed in all Leuconostoc (Le.) mesenteroides, Le. citreum, Lactococcus (Lc.) lactis, Lc. garvieae, and Limosilactobacillus (Lm.) fermentum strains, and in some Lacticaseibacillus (Lact.) casei strains. Most strains exhibited proteolytic activity, reduced pH, and generated organic compounds. Multivariate PCA revealed Le. mesenteroides as a prolific producer of acetic, lactic, formic, and pyruvic acids and acetoin at 30 °C. Enterococcus sp. was distinguished from Lact. casei based on acetic, formic, and pyruvic acid production, while Lact. casei primarily produced lactic acid at 37 °C. At 42 °C, Lactobacillus (L.) helveticus and some L. delbrueckii subsp. bulgaricus strains excelled in acetoin production, whereas L. delbrueckii subsp. bulgaricus and Streptococcus (S.) thermophilus strains primarily produced lactic acid. Lm. fermentum stood out with its production of acetic, formic, and pyruvic acids. Overall, cheese-associated LAB strains exhibited diverse metabolic capabilities which contribute to desirable aroma, flavor, and safety of dairy products.

Impact of lactic acid bacteria and their metabolites on the techno-functional properties and health benefits of fermented dairy products

After conversion of lactose to lactic acid, several biochemical changes occur such as enhanced protein digestibility, fatty acids release, and production of bioactive compounds etc. during the fermentation process that brings nutritional and quality improvement in the fermented dairy products (FDP). A diverse range of lactic acid bacteria (LAB) is being utilized for the development of FDP with specific desirable techno-functional attributes. This review contributes to the knowledge of basic pathways and changes during fermentation process and the current research on techniques used for identification and quantification of metabolites. The focus of this article is mainly on the metabolites responsible for maintaining the desired attributes and health benefits of FDP as well as their characterization from raw milk. LAB genera including Lactobacillus, Streptococcus, Leuconostoc, Pediococcus and Lactococcus are involved in the fermentation of milk and milk products. LAB species accrue these benefits and desirable properties of FDP producing the bioactive compounds and metabolites using homo-fermentative and heterofermentative pathways. Generation of metabolites vary with incubation and other processing conditions and are analyzed and quantified using highly advanced and sophisticated instrumentation including nuclear magnetic resonance, mass-spectrometry based techniques. Health benefits of FDP are mainly possible due to the biological roles of such metabolites that also cause technological improvements desired by dairy manufacturers and consumers.

Effect of starter cultures mixed with different autochthonous lactic acid bacteria on microbial, metabolome and sensory properties of Chinese northeast sauerkraut

Effects of mixed cultures composed of any two of four autochthonous lactic acid bacteria on fermentation of Chinese northeast sauerkraut were investigated in this study. Results indicated that different mixed cultures inoculation generated diversified physicochemical, microbiological and flavor quality of sauerkraut. Compared to spontaneous fermentation, mix-culture fermentation showed significant higher population of lactic acid bacteria and lower amounts of undesirable microorganisms. Free amino acids increased by 2- to 5-fold from initial level in spontaneous and mix-culture fermentation, with the lowest production by spontaneous fermentation. Moreover, mix-culture fermentation promoted the flavor formation based on the analysis of HS-SPME/GC-MS, E-nose, E-tongue and sensory evaluation, especially for the mixed culture of Leu. mesenteroides and L. plantarum. These results highlighted that using a mixed culture made up with Leu. mesenteroides and L. plantarum could be a potential way to improve the quality of sauerkraut, which could provide an alternative way to meet consumers' requirement.

High biodiversity in a limited mountain area revealed in the traditional production of Historic Rebel cheese by an integrated microbiota-lipidomic approach

Historic Rebel (HR) cheese is an Italian heritage cheese, produced from raw milk during the summer grazing period in the Alps. The aim of this work was (i) to characterize the cheese microbiota, by 16S rRNA gene amplicons sequencing, and the volatile and non-volatile lipophilic fraction, by Gas Chromatography and Dynamic Headspace Extraction-Gas Chromatography-Mass Spectrometry, and (ii) to evaluate their respective associations. HR cheese was dominated by Firmicutes phylum (99% of the entire abundance). The core microbiota was formed by Streptococcus, Lactobacillus, Lactococcus, Leuconostoc and Pediococcus genera together representing 87.2–99.6% of the total abundance. The polyunsaturated fatty acids composition showed a high PUFA n-3, PUFA n-6 and CLA content, two fold higher than typical plain cheeses, positively correlated with pasture altitude. A complex volatilome was detected, dominated in terms of abundance by ketones, fatty acids and alcohols. Total terpene levels increased at higher altitudes, being the main terpenes compounds α-pinene, camphene and β-pinene. The HR cheese showed a great diversity of bacterial taxa and lipophilic fractions among producers, despite belonging to a small alpine area, revealing a scarce cheese standardization and a chemical fingerprint of a typical mountain cheese produced during the grazing period. A deeper knowledge of the variability of HR cheese due to its composition in microbial community and volatile compounds will be appreciated, in particular, by elite consumers looking for niche products, adding economic value to farming in these alpine areas.

The Use of Winery by-Products to Enhance the Functional Aspects of the Fresh Ovine "Primosale" Cheese

Fresh ovine "primosale" cheese was processed with the addition of grape pomace powder (GPP). Cheese making was performed using pasteurized ewes' milk and four selected Lactococcus lactis strains (Mise36, Mise94, Mise169 and Mise190) inoculated individually. For each strain the control cheese (CCP) was not added with GPP, while the experimental cheese (ECP) was enriched with 1% (w/w) GPP. GPP did not influence the starter development that reached levels of 10⁹ CFU/g in all final cheeses. The comparison of the bacterial isolates by randomly amplified polymorphic DNA (RAPD)-PCR showed the dominance of the added strains over indigenous milk bacteria resistant to pasteurization. GPP addition reduced fat content and determined an increase of protein and of secondary lipid oxidation. Sensory tests indicated that cheeses CCP94 and ECP94, produced with the strain Mise94, reached the best appreciation scores. Following in vitro simulated human digestion, bioaccessible fraction of ECP94 showed antioxidant capacity, evaluated as radical scavenging activity and inhibition of membrane lipid oxidation, significantly higher than that from CCP94, with promising increase in functional properties. Thus, the main hypothesis was accepted since the functional aspects of the final cheeses improved, confirming that GPP is relevant for sustainable nutrition by using winemaking by-products.

Determination of changes in the microbial and chemical composition of Țaga cheese during maturation

Țaga cheese is a traditional Romanian smear-ripened cheese made from bovine milk and identified with the name of the village and caves where it is produced. As no previously reported microbiological and chemical studies have been undertaken on this product, this research aimed to investigate the microbiological and biochemical characteristics which ensure the uniqueness of Țaga cheese during the ripening process, to inform producers as to key quality determinants. Cheese samples, consisting of retail blocks, were collected on days 2, 5, 12, 18, and 25 of the ripening process. The evolution of lactic microbiota during the production and maturation of traditional cheeses involves isolating lactic acid microorganisms present in cheese. Cheese samples were analyzed for pH, fat, NaCl, fatty acids, and volatile compounds. The microbial ecosystem naturally changes during the maturation process, leading to variation in the microorganisms involved during ripening. Our results show that specific bacteria were identified in high levels during the entire ripening process and may be responsible for milk fat lipolysis contributing directly to cheese flavor by imparting detailed fatty acid flavor notes, or indirectly as precursors formation of other flavor compounds.

Characterization of the key aroma compounds in Yunnan goat milk cake using a sensory-directed flavor analysis

To identify the key aroma compounds in Yunnan goat milk cake, seven varieties of milk cake samples were subjected to sensory analysis and gas chromatography-mass spectrometry (GC-MS), gas chromatography-olfactometry (GC-O), aroma recombination, omission, and addition tests. The GC-MS results revealed 53 compounds with aroma characteristics in all the samples. A further comparison of odor activity values and aroma intensities (AI) revealed 25 of these compounds as the initial key aroma compounds. The contributions of these key aroma compounds to the sensory attributes were determined using a partial least squares regression. Of these compounds, 2-heptanone and 2-nonanone were closely related to the "milky" and "cheesy" attributes and were highly abundant in the samples from Kunming. Fatty acids, including butanoic acid, hexanoic acid, octanoic acid, and decanoic acid, were the most abundant compounds detected in the milk cakes. These fatty acids were closely related to the "rancid" and "animalic (goat)" attributes and were largely detected in the samples from Dali Dengchuan and Dali Xiaguan. Sensory-directed aroma recombination, omission, and addition tests further validated the important contributions of ethyl butyrate, benzaldehyde, 3-methyl-1-butanol, 2-heptanone, hexanoic acid, and octanoic acid to the overall sensory properties. Moreover, ethyl butyrate, benzaldehyde, and 2-heptanone, when added, had evident inhibitory or masking effects on the AI of "sour," "rancid," and "animalic (goat)" attributes. PRACTICAL APPLICATION: Goat milk cake is a popular acid-curd cheese in Yunnan, China, however, our limited knowledge to its key aroma compounds restricts its development and industrial production. In this study, a sensory-directed flavor analysis was used to characterized the key aroma compounds of Yunnan goat milk cake, which will help to enhance our understanding on the flavor profile of Yunnan goat milk cake and provide a reference for optimizing the flavor feature and organoleptic quality of this fresh goat cheese.

Raw Milk Microbiota Modifications as Affected by Chlorine Usage for Cleaning Procedures: The Trentingrana PDO Case

Milk microbiota represents a key point in raw milk cheese production and contributes to the development of typical flavor and texture for each type of cheese. The aim of the present study was to evaluate the influence of chlorine products usage for cleaning and sanitizing the milking equipment on (i) raw milk microbiota; (ii) the deriving whey-starter microbiota; and (iii) Trentingrana Protected Designation of Origin (PDO) cheese microbiota and volatilome. Milk samples from three farms affiliated to a Trentingrana PDO cheese factory were collected three times per week during a 6-weeks period in which a sodium hypochlorite detergent (period C) was used and during a subsequent 6-weeks period of non-chlorine detergent usage (period NC). Samples were subjected to microbiological [Standard Plate Count; coliforms; coagulase-positive staphylococci; and lactic acid bacteria (LAB)] and metagenomic analysis (amplification of V3-V4 regions of 16S rRNA gene performed on Illumina MiSeq platform). In addition, cheese volatilome was determined by SPME-GC-MS. In the transition from period C to period NC, higher SPC and LAB counts in milk were recorded. Milk metagenomic analysis showed a peculiar distinctive microbiota composition for the three farms during the whole experimental period. Moreover, differences were highlighted comparing C and NC periods in each farm. A difference in microbial population related to chlorine usage in bulk milk and vat samples was evidenced. Moreover, chlorine utilization at farm level was found to affect the whey-starter population: the usually predominant Lactobacillus helveticus was significantly reduced during NC period, whereas Lactobacillus delbrueckii had the exact opposite trend. Alpha- and beta-diversity revealed a separation between the two treatment periods with a higher presence of L. helveticus, L. delbrueckii, and Streptococcus thermophilus in cheese samples after NC detergent period. Cheese volatilome analysis showed a slight decrease in lipolysis during C period in the inner part of the cheese wheel. Although preliminary, these results suggest a profound influence on milk and cheese microbiota, as well as on raw milk cheese production and quality, due to the use of chlorine. However, further studies will be needed to better understand the complex relationship between chlorine and microbiota along all the cheese production steps.

Effect of Different Percentage of Camelina sativa Cake in Laying Hens Diet: Performance, Welfare, and Eggshell Quality

Although camelina [Camelina sativa (L.) Crantz] is a good source of protein, antioxidants, and polyunsaturated fatty acids, its antinutritional compounds limit its use in animal feeding. The aim of this study was to verify the effect of feeding laying hens with up to 20% of camelina cake from a breeding line containing a low level of glucosinolates on performance, welfare, and eggshell quality. Two hundred and forty Hy-Line® hens from 18 to 51 weeks of age were divided into three treatments: control (C), camelina cake 10% (CAM10), and camelina cake 20% (CAM20). Egg number was recorded daily, while egg weight, feed consumption, and mortality were recorded weekly. At 24 and 43 weeks of hen age, shell resistance to fracture was measured. Our results demonstrate no detrimental effects for CAM10 and CAM20 diets on feed intake, growth performance, and welfare. No difference in egg production was detected among the diets. The significant (p < 0.05) interaction of diet and age factors suggest that the addition of camelina cake, up to 20%, likely protects the eggshell of older hens. Our findings confirm that camelina cake might be an alternative and sustainable protein source for hens.

Characterisation of Formaggella della Valle di Scalve Cheese Produced From Cows Reared in Valley Floor Stall or in Mountain Pasture: Fatty Acids Profile and Sensory Properties

An important problem in mountain areas is the abandonment of pasture. This trend can be combated by the valorisation of typical dairy products, such as “Formaggella della Valle di Scalve”, a semi-cooked traditional cheese made from whole milk in a mountain area in Italy. The aim of the present research was to compare the fatty acid (FA) profile and the sensory properties of this cheese as manufactured under different conditions: i) from the milk of cows grazing on mountain or valley pasture or fed indoors; ii) from the milk of cows fed hay or fed silage. In the first case, five cheesemaking trials were conducted during two years for each of the following situations: mountain pasture (A); pasture at the bottom of the valley (P) (about 1000m asl); stall (S). In the second case, three cheesemaking trials were conducted for each of the following situations: cows fed silage (I); cows fed hay (F). S cheese was richer in medium-chain FAs, while long-chain FAs were higher in P and A cheeses. On the other hand, long chain fatty acids (LCFA) were more abundant in P and A cheeses than in S. In general, MUFA, PUFA and, consequently, total unsaturated FA (UFA), were significantly higher in the P and A cheeses than S (UFA: 36.55 and 38.34, respectively, vs. 31.13; p < 0.001), while SFA showed higher values in S (68.85 vs. 63.41 and 61.68 in P and A, respectively; p < 0.001). Conjugated linoleic acid isomers (CLA) were more represented in the P and A samples (1.86 in P and 1.52 in A, vs. 0.80 in S; p < 0.001); Omega 3 fatty acids, and in particular α-linolenic acid, were more abundant in P than in S cheese. In winter, the I sample (silage) presented higher percentages of myristic (C14), myristoleic (C14:1) and omega 6 acids, whereas F cheese (hay) contained higher concentrations of CLA. The triangular test of sensory analysis showed that, in general, F cheeses were judged as “sweeter” than I, with aromatic profiles characterized by higher content of 2- butanol and ethyl capronate.