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In this study, a collection of 298 wild strains of lactic acid bacteria (LAB) isolated from raw goat milk cheeses, belonging to 8 genera and 24 species, was investigated for their ability to generate volatile compounds. Sensory evaluation showed that goat milk cultures of Leuconostoc and Lactococcus strains reached the highest scores for dairy odour attributes. Fifty six LAB strains with the highest sensory evaluation scores (one per each ten, or fraction, of those belonging to the same species) were selected for gas chromatography–mass spectrometry (GC–MS) analysis. A total of 34 volatile compounds (five carboxylic acids, eleven alcohols, six aldehydes, six ketones, one ester, and five miscellaneous compounds) were detected in lactic curds made with each one of 56 selected LAB strains. The number of volatile compounds in individual curds varied from 15 to 33 while the total abundance of volatile compounds in individual curds ranged from 1.98- to 17.50-fold the total abundance in uninoculated curd. Major differences in volatile generation were related to amino acid catabolism.

Dynamics of probiotics Lactobacillus rhamnosus LGG, L. reuteri BioGaia, Bifidobacterium animalis subsp. lactis BB12 and B. longum subsp. longum BB536 were investigated during the fermentation of milk supplemented with extracts of Chondrus crispus (CC), Himanthalia elongata (HE), Laminaria ochroleuca (LO), Palmaria palmata (PP), Porphyra umbilicalis (PU), Ulva lactuca (UL) and Undaria pinnatifida (UP). After 24 h at 37 °C, LGG attained counts above 108 cfu/ml in control milk and in milk with all seaweed extracts while BioGaia only attained that level in milk with CC, HE, PP, PU and UL extracts, B12 in milk with UL and UP extracts, and BB536 in milk with CC, HE, PU and UL extracts. In physiological saline, LGG, BioGaia, BB12 and BB536 were respectively stimulated by 4, 0, 5 and 3 seaweed extracts after 24 h at 37 °C and inhibited by 1, 5, 2 and 0 seaweed extracts. Casein and whey proteins added to physiological saline neutralized inhibition caused by UL extract, increasing probiotic counts by 4–5 log cfu/ml, while lactose and citrate had no significant effect. Milk supplementation with seaweed extracts permitted attaining probiotic counts above 108 cfu/ml at the end of fermentation, a result of practical interest for the dairy industry.

The effect of high pressure processing (HPP) at 400 and 600 MPa for 5 min on Laminaria ochroleuca (kombu seaweed) shelf-life during storage at 4 °C for 180 days was investigated. Viable bacterial counts increased in untreated kombu from 5.42 log cfu/g on day 1 to 8.47 log cfu/g on day 60 while they declined in HPP-treated kombu to 2.53–3.62 log cfu/g on day 1 and remained below 3 log cfu/g during storage. Salting with 40% marine salt and freezing at −24 °C also achieved significant decreases of viable bacterial counts, to levels of 3.94 and 2.75 log cfu/g, respectively, on day 60. Kombu pH, dry matter, water activity, colour parameters and texture parameters were significantly influenced by the preservation procedure. Total polyphenol content and antioxidant capacity of kombu samples did not differ on day 1, but on day 180 frozen kombu retained 71.9% of the initial polyphenol content versus 18.7–19.3% in HPP samples and 14.2% in salted samples, and 78.7% of the initial antioxidant capacity versus 22.2–23.1% in HPP samples and 18.3% in salted samples. Proteolytic activity and aminopeptidase activity were more affected by HPP than by salting or freezing on day 1, although all the samples showed similar values afterwards. Industrial relevance HPP, salting and freezing showed to be valid preservation procedures from the point of view of kombu microbiological quality, achieving a shelf-life of at least 180 days. Total polyphenol content and antioxidant capacity remained at higher levels in frozen kombu than in HPP and salted kombu after storage for 180 days.

15 Pág. Departamento de Tecnología de Alimentos​​, Seaweeds are highly perishable foods due to their richness in nutrients. High pressure processing (HPP) has been applied for extending the shelf life of fresh seaweeds but there is no information on the effect of HPP on the bacterial diversity of seaweeds. The culturable bacteria of six species of fresh edible seaweeds (green seaweeds Codium fragile and Ulva lactuca, brown seaweeds Himanthalia elongata, Laminaria ochroleuca and Undaria pinnatifida, and red seaweed Chondrus crispus) were investigated and compared to those of HPP-treated (400 and 600 MPa for 5 min) seaweeds, at the start and end of their refrigerated storage period. A total of 523 and 506 bacterial isolates were respectively retrieved from untreated and HPP-treated seaweeds. Isolates from untreated seaweeds belonged to 18 orders, 35 families, 71 genera and 135 species whereas isolates from HPP-treated seaweeds belonged to 13 orders, 23 families, 43 genera and 103 species. HPP treatment significantly reduced the number of isolates belonging to 6 families and greatly increased the number of Bacillaceae isolates. At the end of storage, decreases in bacterial diversity at the genus and species level were observed for untreated as well as for HPP-treated seaweeds., This study was supported by project AGL 2013-42911-R (Ministerio de Economía y Competitividad, Spain).

Edible seaweeds Chondrus crispus (CC, Irish moss), Codium fragile (CF, green sea fingers), Himanthalia elongata (HE, sea spaghetti), Ulva lactuca (UL, sea lettuce) and Undaria pinnatifida (UP, wakame) were high pressure processed (HPP) at 400 or 600 MPa for 5 min and stored at 4 °C for up to 180 days. Viable bacterial counts on day 1 ranged from 4.24 log cfu/g for UP to 6.14 for CC. Estimated shelf life of control CC, CF, HE, UL and UP seaweeds, with the threshold set at 7 log cfu/g, was 7, 30, 60, 3 and 30 days, respectively. HPP treatments extended shelf life of seaweeds until at least day 180, except for CC treated at 400 MPa, until day 90. Most microbiological, physicochemical, colour, texture and enzymatic characteristics of seaweeds varied significantly with HPP treatment and storage time. HPP treatments generally preserved total polyphenol content and antioxidant capacity of seaweeds until day 180. Exceptions were total polyphenol content of HE and UP and antioxidant capacity of CC and UP, which suffered losses close to half of the initial values. HPP showed to be a valid processing technology for extending the shelf life of edible seaweeds under refrigerated storage.

Kombu seaweed (Laminaria ochroleuca) was preserved by refrigeration at 5 °C (control), by high pressure processing (HPP) at 400 or 600 MPa for 5 min followed by refrigeration at 5 °C, or by freezing at −24 °C. Those treatments were applied to both unsalted and salted kombu samples, which were stored for 180 days. One hundred three compounds belonging to 16 chemical groups were identified in the volatile fraction of kombu. Groups including the highest number of volatile compounds were alcohols (24), aldehydes (13), ketones (10), alkanes (9), haloalkanes (9), alkenes (8) and acids (7). HPP lowered the levels of acids, aldehydes, ketones, lactones + ionones, pyranones and terpenes + terpenoids, and increased alkenes and furans. Freezing lowered the levels of alkanes, aromatic hydrocarbons, pyranones and terpenes + terpenoids, and increased aldehydes, haloalkanes and thiazoles. Salting lowered the levels of pyranones, and increased acids, alcohols, aldehydes, alkanes, aromatic hydrocarbons, furans, haloalkanes, lactones + ionones and thiazoles. Control kombu odour acceptance fell below rejection level on day 60 while HPP-treated kombu showed the highest odour acceptance until day 180. Frozen kombu exhibited abnormal odours whereas salted kombu maintained acceptable odour characteristics. Principal component analysis associated the most relevant groups of volatile compounds with kombu microbiological and sensory characteristics.

Brie cheeses were high pressure (HP)-treated at 400 or 600MPa on days 14 or 21 after manufacture to prevent over-ripening. Lactic acid bacteria and Penicillium camemberti numbers declined markedly after HP treatment. In control cheese pH increased 2.0 units from day 21 to day 60, but less than 0.3 units in HP-treated cheeses. Cheeses treated at 600MPa showed the maximum concentrations of residual caseins during refrigerated storage and control cheese the minimum concentrations. A 7.6-fold increase in hydrophobic peptides was recorded from day 21 to day 60 in control cheese and 0.8-1.6-fold increases in HP-treated cheeses. The maximum aminopeptidase activity was detected in control cheese, the highest free amino acid concentrations in cheeses treated at 400MPa. The firmest texture was recorded for cheeses treated on day 14 at 400 or 600MPa. HP-treated cheeses showed higher flavour quality scores than control cheese from day 60 onwards. © 2014 Elsevier Ltd.

Lactic starters used for cheese manufacture play an important role in the production of bitter peptides and their degradation to non-bitter products. The oligopeptide transport system (Opp) of lactococci is essential for milk peptide utilization. The periplasmic substrate binding protein serves to capture the substrate with high affinity and to deliver it to a membrane-bound complex that translocates it inside the cell. Prt+- and Lac+- derivatives of MG1363 ΔoppA strains expressing a wild-type MG1363 OppA or a mutant OppA with a single point mutation at residue 471 (OppA(D471R)) from a plasmid were constructed. These strains were used as lactic starters in cheese manufacture to improve flavour quality by removing hydrophobic peptides from the cheese matrix, through their preferential transport by OppA(D471R). Cheeses made with these strains were not significantly different from control cheeses after 1 day of ripening with respect to bacterial counts, pH and proteolysis, and only slight differences were recorded after 9 and 20 days of ripening. HPLC chromatograms of the hydrophilic and hydrophobic peptides present in the water-soluble fraction of experimental cheeses showed significant differences in peptide content as well as in peak profiles. These results suggest a different peptide utilization in the strain expressing OppA(D471R) and make it suitable for use as starter to improve cheese quality. © 2005 Elsevier B.V. All rights reserved.