Formation Of Off-flavours Research Articles

Impact of lactic acid bacteria starter inoculation on the Physico-chemical, microbiological, volatiles and sensory properties of natural black Gemlik (Olea europaea L., cv.) table olives

Traditionally, the fermentation of Gemlik table olives takes place spontaneously by the endogenous microbiota in Turkey, but the uncontrolled process during fermentation can result in the formation of off-flavours and a low sensory quality of the final product. In this research, the effects of inoculating naturally black Gemlik olives with Lactiplantibacillus pentosus and Lactiplantibacillus plantarum starter cultures on lactic fermentation development, volatile compounds, and sensory properties were investigated. Changes in spontaneous and culture inoculated olives were monitored during fermentation. Compared to spontaneous fermentation, rapid acidification, and sugar depletion were achieved with the use of starter cultures. Extra lactic acid bacteria and total yeast growth were detected in the inoculated trials during fermentation compared to the control trial. Volatile compounds in olives were extracted by the Purge and Trap method. 46 volatile compounds from 10 chemical groups have been identified in olives. In all three trials, volatile acids were the group of volatile compounds found in the top amount in olives, higher alcohols, phenols, aldehydes/ketones, and terpenes followed the volatile acids. Phenyl ethyl alcohol, α-farnesen, (Z)-3-hexene-1-ol and 2-hexanol, which give pleasant flavors, were determined to be in more quantity in olives with inoculated starter cultures. This study reveals that the use of starter culture provides advantages in the production of Gemlik variety table olives, positively affects aroma development, and improves sensory properties.

Effect of Lactobacillus plantarum and Staphylococcus xylosus on flavour development and bacterial communities in Chinese dry fermented sausages

The use of starter cultures helps to improve the quality and safety of traditional meat products. In this study, the effects of Lactobacillus plantarum R2 and Staphylococcus xylosus A2 inoculation on microbial community, lipolysis, proteolysis, and volatile compounds in Chinese dry fermented sausages were investigated. Culture-dependent and culture-independent high-throughput sequencing) methods were employed to evaluate the bacterial communities. Results showed that the total contents of free fatty acids (FFAs) and free amino acids (FAAs) were increased by inoculating the starter cultures, especially a mixed culture. A significant decrease in pH and water activity was observed in the inoculated sausages (p < 0.05). Moreover, the inoculation treatment enhanced the competitiveness of dominant bacteria and inhibited the growth of unwanted bacteria. This was beneficial to promote the release of FFAs and FAAs and to prevent the formation of off-flavours and rancidity. Thus, the flavour development in the inoculated dry fermented sausages was attributed to the improvements in microbiological quality.

SO2, high pressure processing and pulsed electric field treatments of red wine: Effect on sensory, Brettanomyces inactivation and other quality parameters during one year storage

Abstract The use of sulphur dioxide (SO2), high pressure processing (HPP) and pulsed electric fields (PEF) for wine preservation was compared. The difference between HPP and PEF wines and untreated wine after one year's storage, in terms of sensory quality, B. bruxellensis inactivation, colour density, total phenolic content and volatile phenol concentration, was determined. SO2 and HPP led to >5 log inactivation of B. bruxellensis, however SO2 treated cells were able to recover after 10 months storage. PEF treatment provided insufficient inactivation (0.8 log reduction). HPP was the only treatment which prevented Brettanomyces growth and the formation of off-flavours and –odours after storage. SO2 and PEF treatments had no significant effect on wine quality, while the colour and phenolic quality of HPP treated wine deteriorated after six months. HPP and PEF also had no effect on the overall sensory quality of the wines. Overall, HPP was able to produce a microbiologically stable wine, with no effect on the taste of the wine. Industrial relevance Brettanomyces is a spoilage concern in the wine industry, conventionally controlled using SO2. Due to its adverse effects on some consumers, the use of emerging non-thermal technologies has started to garner great interest in the food and beverage industry. The results show that HPP is a non-thermal treatment with the potential to reduce the use of SO2 for the preservation of wine in the industry. However, to extend the quality of HPP treated wine beyond six months storage and retain wine colour and total phenolic content, small doses of SO2 may be required. Since, PEF is a continuous process, integration of this technology into current wine production practices would be less challenging than for HPP. This study also underscores the importance on conducting regular tests for B. bruxellensis contamination in the wine industry, because even when plate counts are negligible this yeast has the ability to recover when conditions become favourable again.

Iron-Polyphenol Interaction Reduces Iron Bioavailability in Fortified Tea: Competing Complexation to Ensure Iron Bioavailability

Tea seems to be like a logical substrate for iron fortification; however, its fortification with iron presents technical challenges as tea polyphenols form a blue complex with iron that makes both of them unavailable for absorption. The objective of this work was to develop an effective technology, to prevent the interaction of iron and polyphenols by using EDTA as a competing complexing agent. Fortified tea was prepared from premix, prepared by spraying iron and sodium EDTA into tea leaves. Iron concentration in tea was adjusted to 5 mg/cup. Iron content was measured by AAS and the iron-polyphenol complex by spectrophotometry at 560 nm. Sensory evaluation was carried out in order to determine if fortification affects the properties of tea. A molar ratio of 1 : 2 Fe : EDTA was able to avoid complex formation and provide 4 mg of iron per cup of brewed tea. The fortified tea had a similar colour and flavour as ordinary tea, without the development of off-flavours. However, fortified tea with a ratio lower than 1 : 2 had a darker colour and off-flavours. By the addition of EDTA in a molar ratio ≥1 : 2, it is possible to produce an iron fortified tea without the formation of off-flavours.

Inactivation of microorganisms by UV-treatment of must and wine

The objective was to investigate the applicability of UV-C technology to inactivate yeasts and bacteria in must and wine. Experiments were carried out in vintage 2016 with Riesling musts of different quality containing their natural microflora. Yeasts were tested more resistant to UV-C energy than bacteria. Saccharomyces cerevisiae showed higher tolerance against UV-C irradiation than Hanseniaspora uvarum facilitating new opportunities to control spontaneous fermentations. However, inactivation efficacy was strongly dependent on turbidity of musts and the initial degree of contamination suggesting a shadowing effect of individual germs. Compared with thermal pasteurization, UV-C treatment of must with 1 kJ/L showed similar effects in germ-reduction. While thermal pasteurization significantly decreased aroma precursors in musts, UV-C treatment did not change concentrations of glycosidically-bound C6-alcohols, monoterpenes and C13-norisoprenoids as shown by GC-MS analysis. Applying UV-C technology in wines, it was possible to irreversibly stop ongoing alcoholic fermentation indicating that UV-C treatment is capable to replace SO2 addition to produce wines with residual sugar. Besides inactivation power, UV-C is known for its ability to form powerful off-flavours such as methional or methanethiol. Sensory analysis revealed that the application of UV-C at doses < 2 kJ/L in must is uncritical. However, applying UV-C after alcoholic fermentation can result in rising concentrations of mercaptans already at doses < 1 kJ/L. In this context, compounds such as caftaric acid, riboflavin and dissolved oxygen are thought to positively contribute to the UV-induced formation of off-flavours in wine.

Preliminary findings on the effect of light-oxidation on Asiago d’allevo vecchio protected designation of origin cheese

Food is exposed to light during processing, packaging, distribution and retail storage, resulting in deterioration of the product quality. Milk and other dairy products are among the most sensitive due to the high content of riboflavin, vitamin B2, which is an efficient photosensitizer for oxidative processes. Photooxidation in cheese induces degradation of nutritional quality such as proteins, lipids, and vitamins. Moreover, it causes formation of off-flavours, off-odours and gradual bleaching. The objective of this study was to evaluate the effect of light exposition on sliced Asiago d’allevo cheese (lowland vs alpine) aerobically packaged stored for 336 h under both fluorescent light and in the dark. Alpine cheese showed higher b * (P<0.001) and a * indexes (P<0.001) and also a higher lipid oxidation (P<0.01) than lowland one. Riboflavin content was significantly higher (P<0.001) in lowland cheese. Cheese samples exposed to the light were significantly lighter (P<0.001) than those exposed in the dark and they also showed a decrease in yellowness (P<0.001) and redness (P<0.001) as well as in riboflavin content (P<0.001). Lipid oxidation did not produce statistically significant change. Storage time significantly affected riboflavin content (P<0.001), TBARs (P<0.001) and cheese colour (P<0.001). Results suggest that light exposition had a pronounced effect on cheese characteristics.

Chemical changes in wheat pan bread during storage and how it affects the sensory perception of aroma, flavour, and taste

Wheat bread and whole wheat bread were stored for up to 3 weeks and specific chemical reactions were related to perceptual flavour changes as analysed by sensory profiling. Volatile and non-volatile compounds were quantified using GC–MS and HPLC. Results were examined by multivariate data analysis.Fresh wheat bread had a higher concentration of the fermentation products 2,3-butandione and 3-hydroxy-2-butanone and the Strecker aldehydes 2- and 3-methylbutanal. The fresh bread and bread stored for 1 week were described by dough and bran aroma and flavour whereas samples stored 2 and 3 weeks were characterised by dust aroma and flavour together with bitter taste. Bread stored 2 and 3 weeks generally had a higher content of secondary lipid oxidation products than the more fresh samples. The total content of soluble phenolic acids stayed unchanged during storage.Most sensory attributes could be directly related to changes in the chemical composition of volatiles. The formation of off-flavours in bread could be related to the formation of secondary lipid oxidation products together with decreasing levels of compounds from Maillard reactions.

Exogenous methyl jasmonate diminishes the formation of lipid‐derived compounds in boiled potato (Solanum tuberosum L.)

During potato storage the tubers tend to develop off-flavours, mainly due to lipid-derived aldehydes, whose formation is increased after boiling or processing. This may become a problem when boiled or precooked potatoes are used. Methyl jasmonate (MJ) is a phytohormone capable of modifying plant and food composition. The aim of this work was to control the formation of off-flavours in different cultivars of raw potato during storage by MJ treatment. The use of Carbowax 20M as support in MJ emulsion resulted in significantly (P < 0.05) lower levels of lipid-derived compounds than the use of lanolin. Levels of the lipid-derived aldehydes propanal, hep-2-enal, nonanal, oct-2-enal and hexanal, although dependent on variety, generally decreased significantly (P < 0.05) after treatment with MJ/Carbowax 20M emulsion. Sugar-derived compounds such as pyridine and furfural, however, were not affected by this treatment. Treatment with MJ/Carbowax 20M can be used to diminish the formation of off-flavours in boiled potato. However, this treatment is not useful to avoid the sweetening caused by sugar-derived products. Additional advantages of exogenous MJ are a delay in the appearance of sprouting and aging and hence prolongation of the storage life of potato tubers.

Inhibition of citral degradation in model beverage emulsions using micelles and reverse micelles

Citral is a flavour component that is widely used in the beverage, food, and fragrance industries. Citral chemically degrades over time in aqueous solutions due to acid catalysed and oxidative reactions, leading to loss of desirable flavour and the formation of off-flavours. We examined the influence of surfactant micelles (Tween 80) in the aqueous phase and reverse micelles (polyglycerol polyricinoleate, PGPR) in the oil phase on the oil–water partitioning and chemical degradation of citral in medium chain triglyceride oil-in-water emulsions. The percentage of citral in the aqueous phase of the emulsions increased with increasing Tween 80 concentration, which was attributed to its incorporation within surfactant micelles. The rate of citral degradation decreased as the Tween 80 concentration was increased from 1% to 5% w/w in both aqueous solutions and in emulsions, suggesting that citral was protected from degradation once it was incorporated into micelles. The presence of reverse micelles (5% or 10% w/w PGPR) in the oil droplets decreased the percentage of citral present within the aqueous phase of the emulsions, suggesting that citral was preferentially incorporated into the reverse micelles. In addition, the presence of reverse micelles increased the chemical stability of citral, possibly because a greater fraction remained within the oil droplets. These results show that micelle or reverse-micelle structures may be used to improve the chemical stability of citral in beverage emulsions.

Investigation of off-odour and off-flavour development in boiled potatoes

The present study focused on the development of a sensory evaluation system, using a quantitative descriptive analysis (QDA) scheme, to define the sensory attributes of boiled potato slices. A HS-SPME–GC–MS technique for a rapid determination of volatile components in boiled potatoes was also investigated. In addition to the mechanism of generation of off-odours and off-flavours in boiled potatoes (POF), the effects of the use of food additives after cooking were examined. POF formation, analysed by both sensory evaluation and HS-SPME, demonstrated an oscillating mechanism of formation of volatile compounds, probably related to enzymatic lipid oxidation and hydroperoxide generation. In particular, POF were strongly correlated with the presence of 2-pentenal, 2-hexenal, 2-heptenal, 2-pentylfuran and 2-decenal. In all, about 50 compounds were detected by HS-SPME technique. Treatment with ascorbate or citrate, after cooking and before storage, did not prevent the formation of off-flavours, in contrast to sodium pyrophosphate. Potassium meta-bisulphite prevented POF formation, but caused the creation of other off-flavours detected by a trained panel.

Effect of hydroxycinnamic acids on lipid oxidation and protein changes as well as water holding capacity in frozen minced horse mackerel white muscle

The antioxidant effectiveness of different hydroxycinnamic acids for inhibiting the formation of off-flavours associated to rancidity in minced frozen horse mackerel white muscle stored at −10 and −18 °C was studied. The influence of lipid oxidation on protein aggregation, protein denaturation and water holding capacity was also determined. Caffeic acid, o-coumaric acid and ferulic acid were the antioxidants tested. The order of antioxidant effectiveness was caffeic acid > ferulic acid > o-coumaric acid accordingly with previous results obtained in chilled horse mackerel. A strong dependence of antioxidant effectiveness to the ratio lipid/antioxidant concentration was observed. There was no evidence to suggest that antioxidants reduce protein aggregation or water holding capacity changes. Protein aggregation was not accompanied by gross protein denaturation, as monitored by differential scanning calorimetry. No evidence was found for a link between extent of lipid oxidation and degree of protein aggregation or water holding capacity changes.

Transformações bioquímicas de abacaxi minimamente processado armazenado sob atmosfera modificada

Realizou-se estudo sobre a influência da atmosfera modificada com diferentes concentrações de gases durante o armazenamento de abacaxi cv. Smooth cayennne minimamente processado, por oito dias, à temperatura de 5ºC e 85% de UR. Foram realizadas análises de açúcares neutros, celulose, hemicelulose e poliuronídeos totais na parede celular. O abacaxi minimamente processado foi acondicionado sob duas Atmosferas Modificadas Ativas, uma com 5% de O2 e 5% de CO2 (AM1),outra com 2% de O2 e 10% de CO2 (AM2),e uma Atmosfera Modificada Passiva (Controle) durante 8 dias de armazenamento. O uso de atmosferas modificadas ativas permitiu que o abacaxi minimamente processado sofresse menor degradação da parede celular com menor solubilização das hemiceluloses. Abacaxis minimamente processados e armazenados sob atmosfera modificada obtiveram uma vida de prateleira média de 6 dias, a 5º C.

Prevention of condensation damage to cocoa beans shipped in containers

When cocoa is shipped in unlined general purpose shipping containers condensation on the internal surfaces of the containers frequently leads to deterioration. Two trial shipments of cocoa were made between Papua New Guinea and Australia to evaluate single-trip insulating linings of 12 mm insulating board and aluminium-faced buiding paper, and also the use of an additional drying process before loading, as means of minimizing condensation damage. Evaluation was based on visual examination for the presence of condensate, temperature and humidity measurement in the head space, measurement of the moisture content of samples of cocoa beans, and on sensory evaluation of chocolate prepared from cocoa samples. Condensation was found to occur only after arrival in Australia. Building paper was found to be ineffective, and re-drying was accompanied by the formation of off-flavours. However, the insulating board was found to give adequate protection against the damage while introducing no off-flavours.