New bread formulation with improved rheological properties and longer shelf-life by the combined use of transglutaminase and sourdough

The combined use of the protein reticulating enzyme transglutaminase (TGase) and a selected microbial consortium of Lactobacillus sanfranciscensis and Candida milleri for improving the rheological properties, aroma, and shelf-life of a bakery product was evaluated. A microbial TGase, showing the highest activity over a wide temperature range on different protein substrates, was selected among different types. Results showed that this TGase was able to produce isodipeptide bonds, especially in the gluten fraction, leading to the formation of protein aggregates, which improved the structure of a sourdough bakery product. The microbial TGase in combination with sourdough exhibited a positive synergistic effect allowing the production of flavor-enriched bread, with rheological properties similar to those of standard bread

Cinetica della fermentazione alcolica e arresti di fermentazione

Cinetica della fermentazione alcolica e arresti di fermentazione (Maria Elisabetta Guerzoni, Diana Isabella Serrazanetti) ............................................................ “ 57 4.1 Introduzione .......................................................................................................................... “ 57 4.2 Dipendenza dal ceppo .......................................................................................................... “ 58 4.3 Risposta agli stress ................................................................................................................ “ 60 4.3.1 Stress osmotico .......................................................................................................... “ 60 4.3.2 Stress nutrizionale ...................................................................................................... “ 61 4.4 Importanza e frequenza degli arresti di fermentazione ......................................................... “ 62 4.5 Possibili fattori causali delle fermentazioni problematiche ................................................... “ 63 4.6 Ioni e squilibro ionico ............................................................................................................ “ 65 4.7 Temperatura e processi fermentativi ..................................................................................... “ 67 4.8 Etanolo e membrane cellulari ............................................................................................... “ 69 4.9 Conclusioni ............................................................................................................................ “ 71 Bibliografia ............................................................................................................................ “ 72Il Volume, a cui hanno collaborato ricercatori italiani noti per i loro studi nel campo, vuole fissare lo stato dell\u92arte sottolineando gli aspetti più rilevanti della ricerca. Tra gli argomenti principali trattati nel testo figurano l\u92ecologia microbica delle uve e dei mosti d\u92uva, le interazioni e gli aspetti metabolici positivi e negativi della crescita microbica sulla qualità e tipicità dei vini e sulla produzione di alcuni vini speciali. Particolare attenzione è stata data alla tassonomia, fisiologia, metabolismo, genomica di Saccharomyces cerevisiae. Principali argomenti trattati nel Volume: La fermentazione spontanea \u96 Saccharomyces cerevisiae \u96 Saccharomyces cerevisiae: metabolismo primario e produzione di aromi nel vino \u96 Cinetica della fermentazione alcolica e arresti di fermentazione \u96 La rifermentazione dei vini \u96 I vini ad invecchiamento biologico \u96 I lieviti non-Saccharomyces \u96 Batteri lattici nel vino \u96 I batteri acetici \u96 Ricerca, identificazione e caratterizzazione dei lieviti vinari \u96 Uso di colture starter e impiego di lieviti e batteri lattici in cantina \u96 Botrytis cinerea, marciume nobile e marciume grigio

2-methyibutyric and 3-methylbutyric acids: possible components of a feed back loop under stress conditions?

The exposure of lactic acid bacteria (LAB) to stressful conditions during fermentation involves a broad transcriptional response with many induced or repressed genes. The complex network of such responses will reflect upon the composition and organoleptic properties of the dough and final products. The over-production of 2-methylbutyric (2MetBut) and 3-methylbutyric (3MetBut) acids, by LAB, has been detected following exposure to different sublethal stress conditions. Serrazanetti et al. (2011) reported the over-production of these two compounds in Lactobacillus sanfranciscensis during acidic stress when the cells were grown in the presence of leucine (Leu) as the only branched chain amino acids (BCAAs) source. Metabolites coming from BCAAs catabolism increased up to seven times under acid stress (pH 3.6 and 5.8). Moreover, the gene expression analysis confirmed that some genes associated with BCAAs catabolism were overexpressed under acid conditions. The experiment with labelled Leu showed that 2MetBut originated also from Leu. While the overproduction of 3MetBut under acid stress can be attributed to the need to maintain a redox balance, the rationale for the production of 2MetBut from Leu can be found in a newly proposed biosynthesis pathway leading to 2MetBut and 3 mol of ATP per mol of Leu. But why do LAB need to catabolize in excess BCAAs in the presence of sublethal stress if they do not generate energy? A possible answer, suggested by Goffin et al. (2010), lies in the end products of BCAAs catabolism, a number of which could serve as signalling molecules for the interaction of Lactobacillus plantarum with its environment and maybe itself. In order to support this hypothesis the possible signalling-effect of 2MetBut and 3MetBut on the growth and the metabolism of some strains of LAB has been investigated. In particular, L. plantarum, L. sanfranciscensis and Lactobacillus brevis were exposed to BCAAs catabolism end products for 2 and 24 hours after which the volatile metabolites and the expression of some genes involved in Leu catabolism were analysed by GC-MS-SPME and RT-PCR, respectively

POTENTIAL OF HIGH PRESSURE HOMOGENIZATION AND FUNCTIONAL STRAINS FOR NOVEL FUNCTIONAL DAIRY FOODS

Functional foods are one of the fastest increasing fields in the global food industry since they are positively perceived by the consumers as dietary strategy to reduce the incidence of illness in the humankind. Actually, the use of biotechnological strategies, based on the use of functional and specific strains and sustainable technologies, such as high pressure homogenization, can be a great chance to create innovation in dairy field. Critical discussion on the actual scenario will be the main topic of this chapter

Improving the functional and sensorial profile of cereal-based fermented foods by selecting Lactobacillus plantarum strains via a metabolomics approach

Metabolomics was recently applied in food science for monitoring the quality, processing, safety, and microbiology of both raw materials and final products to improve the consumer's health and confidence.The present work aimed at using a metabolomics approach to detect the flavour and antioxidant profiles characteristic of different . Lactobacillus plantarum strains in sourdoughs of durum wheat and KAMUT® khorasan wheat. The study was developed to improve sensorial and functional properties of cereal-fermented foods through the selection of optimal flour-microbial strain combinations. A large set of metabolites, including volatile compounds, polyphenols and flavonoids, was taken into consideration and the antioxidant activity was determined. The metabolic profiles were combined by using heat maps to visualise the result of a hierarchical clustering of profile data. In KAMUT® khorasan wheat-fermented dough, a high correlation was found between a group of volatiles (5 alcohols, 6 carbonils, dodecanoic acid and 1,3-hexadiene) and the polyphenolic compounds gallic acid (GA), epigallocatechin-gallate (EGCG), epigallocatechin (EGC), flavonoids (Flav), protocathecuic acid (Prot ac) and total polyphenols (Polyp). In durum wheat dough a different pattern of volatile molecules (10 alcohols, 5 carbonils, 3 acids and 3 hydrocarbons) resulted highly correlated with EGC, EGCG, Flav and Polyp. The results also evidenced a simultaneous increase of sensorial and health promoting compounds when using . L. plantarum strains 98A and 6BHI in fermented durum wheat dough, while 94A and 206 strains had their highest performance with KAMUT® khorasan wheat dough. Our data show that metabolomics may represent an important tool for the rapid selection of strain/substrate combinations to simultaneously increase sensorial and health beneficial characteristics

Effect of fermentation on the content of bioactive compounds in tofu-type products

Tofu is part of Asian cuisine and may be the most popular food made from soy. Due to the influence of processing on some compounds (fatty acids, tocopherols, phospholipids, sterols and phenolic compounds) content of soy food products, soybean flour, traditional tofu and tofu obtained by soymilk fermentation were studied. Fermentation was performed using lactic acid bacteria, such as Lactobacillus casei and Lactobacillus acidophilus. Fermentation by lactic acid bacteria plays an essential role in the reduction of isoflavones glycosides/aglycone ratio (from 0.14 to 0.89 in traditional and fermented tofu, respectively) and in the higher bioavailability of isoflavones, however it does not significantly affect soybean fatty acids and tocopherols. This behaviour suggests the use of these microorganisms to enhance the added value of soybean products, and promote the selection of tailor made starter culture able to growing well in soy milk and contemporary to produce bioactive compounds for specific consumer's categor

Combination of transglutaminase and sourdough on gluten-free flours to improve dough structure

The aim of this work was to evaluate the effects of microbial transglutaminase (mTG) and sourdough on gluten-free (GF) flours. Besides deamidation and incorporation of amines, mTG catalyses protein cross-links, modifying dough structure. Sourdough from lactic acid bacteria (LAB) and yeast modifies dough protein composition, determining proteolysis, which induce the formation of aroma precursor metabolites. The chemical-physical interactions of volatile molecules with various constituents of the matrix affect the retention of aroma compounds. Here, the effect on volatile molecule profiles and on protein networks formation after mTG treatment in sourdoughs obtained with four GF flours belonging to cereals, pseudo-cereals and legumes (rice, corn, amaranth and lentil) was investigated. Sourdough was prepared with a two-step fermentation using Lactobacillus sanfrancisciensis (LSCE1) and Candida milleri (PFL44), then mTG was added after 21\ua0h of fermentation at increasing levels. The results showed that mTG had the capacity to modify GF flour proteins and improve protein networks formation, involving mainly the prolamin protein fraction. This is particularly relevant for the production of GF backed goods generally lacking of technological, structural and sensorial features compared with products obtained with wheat flour sourdough fermentation. Interestingly, mTG treatment of sourdough affected also the volatile composition and indeed possibly the final organoleptic properties of the products

Volatile Profiles and Mannoprotein content in Saccharomyces cerevisiae strains of enological interest

Introduction: Volatiles from fermentation dominate wine flavour, since yeasts affect the quality of the grape prior to harvest and, during fermentation, they metabolise grape sugars and other components into alcohols, esters, organic acids and aldehydes (Fleet, 2003). So the production of volatile compounds is become one of the major technological character for yeast selection. Among the new technological features, also the production of mannoprotein has gained interest. In this perspective, main aim of this work was to characterize 10 strains of S. cerevisiae for their volatile molecule profiles and the release of mannoproteins in trebbiano wines. Results and Discussion: The strains, inoculated at level of 4.9 and 6.3 log cfu/ml but only the strains L318 and 12233X6167 were able to reach values of 7.5 log cfu/ml. The volatile molecule profiles were characterized by a great amount of alcohols and in any case, the profiles obtained can be considered as a strain fingerprinting. According to the principal component analysis, the strains L288, L234 and L318 were characterized by the presence of propanoic acid, butanol, octanoic acid and 3 methyl pentanol while the strain 12233_35G2 was characterized by the presence of decanoic acid ethyl ester, eptanoic acid ethyl ester, acetic acid 2 phenetyl ester. Regarding mannoproteins, the strain 12233_6167 produced 104 mg/l in trebbiano wine. The data permitted to select the strains endowed with the best volatile molecule profiles for Trebbiano wine and able to release the major content of mannoproteins. Moreover, the good potential of the infra-red spectroscopy was demonstrated for mannoprotein evaluation

New insights in thermal resistance of staphylococcal strains belonging to the species Staphylococcus epidermidis, Staphylococcus lugdunensis and Staphylococcus aureus

In this study the thermal resistance of seven strains of staphylococci was studied. Three of them (two Staphylococcus epidermidis and one Staphylococcus lugdunensis) were isolated from pasteurized tofu, while one Staphylococcus aureus from fermented sausages. Also the corresponding type strains were tested. Their heat resistance was assessed at 80 C also in relation to different growth conditions (high NaCl concentrations and low pH). Moreover, the effect of two terpenes (carvacrol and citral) on their survival during thermal treatment was assessed. All the strains were able to survive a 20 min thermal treatment and showed a similar behavior, i.e. an inactivation of about 6 log units in the first 2e4 min of treatment, followed by constant survivor counts (2e4 log CFU/ml). The pre-culture of staphylococci under stressing conditions (high NaCl concentration and low pH) increased the susceptibility to thermal treatment in three strains isolated from food matrices. The addition of carvacrol and citral during thermal treatment influenced the number of survived cells at the end of the treatment. This new insight in the thermal resistance of staphylococci needs to be better investigated, in order to study proper strategies to control their occurrence and behavior in real food systems