Biochemical, microbiological and technological characteristics of type II sourdoughs produced with lactic acid bacteria single-strains

The interplay between biochemical characteristics and the generation of volatile compounds in 11 type II sourdough fermented by single strains of lactic acid bacteria (LAB) was studied. Samples were collected at 0, 6, 9, 12, 15, 18 and 24h for analyses of microbial growth, pH, titratable acidity and CO2 production. During the first 12h, the LABs entered the stationary phase, and the formation of organic and carboxyl acids, alcohols, and esters were observed. Although acidity is an important characteristic of sourdough, in this work increasing the acetic acid content decreased yeast growth and the CO2 retention capacity of the doughs. The main carbohydrate consumed by autochthonous yeast was influenced by the LAB added (homo-or heterofermentative), as observed by correlation analysis. Maltose and glucose showed a strong and negative correlation with the yeast cell density in the dough fermented by homo and heterofermentative LAB, respectively. Moreover, LAB had an important effect on the aromatic profile, being the alcohols, aldehydes, alkanes, organics acids and esters mainly groups characterized. Altogether, 100 different volatile compounds were identified; however, each dough had a different volatile profile. This study shows, for the first time, the influence of a single strain of LAB on the characteristics of type II sourdough.

Potassium and growth-promoting fungi improve the postharvest quality of grape tomato

Tomato plants respond well to potassium fertilization, whose insufficiency leads to a drop in fruit production and quality. On the other hand, the association of growth-promoting fungi (GPF) with roots has been shown to be able to optimize nutrient absorption, which implies lower financial costs and a decreased risk of loss of K applied to the soil. The objective of this study was to investigate the effects of inoculation with GPF and K rates on the postharvest quality of grape tomato hybrid ‘Mascot’ grown in a hydroponic system. The plants were cultivated in a hydroponic drip system using washed and sterilized sand as substrate. They were trained with two stems, leaving three bunches per stem. The experiment was carried out in a splitsplit-plot arrangement in a completely randomized design with three replicates. Ripe fruits were stored for 30 days in PET containers in storage chambers at a temperature of 25 °C. After 0, 10, 20 and 30 days of storage, five fruits were collected to determine the titratable acidity (TA) and soluble solids (SS), reducing sugars (RS) and vitamin C contents. The K rates provided an increase in the quality attributes. At low K rates, inoculation with GPF led to higher TA, SS, RS and vitamin C values. Inoculation of the plants with GPF improved the postharvest preservation of the fruits, especially when the plants underwent nutritional stress during cultivation.

Microbiological dynamics involved in cereal-porridge production using maize and sorghum

Cereal-porridge(‘ogi’) was produced by spontaneous fermentation using maize and sorghum substrates. The microbiological dynamics involved were monitored over a period of 48h fermentation. Bacteria, yeasts and moulds were isolated. Based on the morphological, cultural and biochemical test results, the aerobic bacterial isolates were identified as Proteus vulgaris, Proteus mirabilis, Klebsiella sp, Staphylococcus aureus, Lactobacillus sp, Pseudomonas sp, Citrobacter sp, Bacillus sp, Proteus sp, Shigella sp, and Escherichia coli. The Lactic acid bacteria were Lactococcus sp, Enterococcus sp, Lactobacillus fermentum, Lactobacillus sp. The yeast isolates were 2 strains of Saccharomyces cerevisiae, one other Saccharomyces sp and a Candida sp. The moulds were Aspergillus niger, Aspergillus flavus, Rhizopus sp and Penicillium sp. The lactic acid bacteria (LAB) isolated were 2 strains of Lactococcus lactis, 2 Enterobacter spp, 5 strains of Lactobacillus fermentum and 1 other Lactobacillus sp. The initial total viable aerobic bacterial count at 0h in maize, sorghum and maize-sorghum blend were 4.6 × 104, 7.3 × 104 and 2.4 × 105cfu/ml respectively. The growths rose to peaks of 6.5 × 107 and 3.9 × 107cfu/ml at 24h in maize and maize-sorghum blend, respectively. A Peak of 4.7 x 107cfu/ml was attained at 36h in sorghum. Coliform bacteria and moulds growths in the three samples attained peaks of growth at 12h and reduced till there was no growth by 48h. Lactic acid bacteria and yeasts increased in numbers till the end of fermentation. The initial pH value at 0h was lowest in maize-sorghum blend sample (5.43) and highest in maize (5.75). Final values at 48h were 3.76, 3.78 and 3.75 in maize, sorghum and maize-sorghum blend samples respectively. There were no significant differences between the microbial growth patterns, changes in pH, total titratable acidity (TTA) and amylase enzymatic activities in maize, sorghum and maize-sorghum blend samples during fermentation.

The Combined Effect of Hot Water Treatment and Chitosan Coating on Mango (Mangifera indica L. cv. Kent) Fruits to Control Postharvest Deterioration and Increase Fruit Quality

The synergistic effect of dipping in 55 °C for 5 min of hot water (HW) and 1% chitosan coating during the storage of mango at 13 ± 0.5 °C and 85%–90% relative humidity for 28 days was investigated. The combined treatment significantly suppressed the fruit decay percentage compared with both the single treatment and the control. In addition, the specific activities of key plant defense-related enzymes, including peroxidase (POD) and catalase (CAT), markedly increased. The increase occurred in the pulp of the fruits treated with the combined treatment compared to those treated with HW or chitosan alone. While the control fruits showed the lowest values, the combination of pre-storage HW treatment and chitosan coating maintained higher values of flesh hue angle (h°), vitamin C content, membrane stability index (MSI) percentage, as well as lower weight loss compared with the untreated mango fruits. The combined treatment and chitosan treatment alone delayed fruit ripening by keeping fruit firmness, lessening the continuous increase of total soluble solids (TSS), and slowing the decrease in titratable acidity (TA). The results showed that the combined application of HW treatment and chitosan coating can be used as an effective strategy to suppress postharvest decay and improve the quality of mango fruits.

Sodium Nitroprusside Functions in Browning Control and Quality Maintaining of Postharvest Rambutan Fruit

Surface browning after harvest is the primary constraint affecting the storage life and market circulation of rambutans. In this study, rambutan fruits were soaked in sodium nitroprusside at different concentrations and stored at 25°C for 8 days to explore the effects on postharvest quality and browning. The weight loss, browning index and superoxide anion radical, hydrogen peroxide and malondialdehyde contents of the treated fruits were reduced compared to those of the control fruits (soaked in distilled water). And fruits treated with sodium nitroprusside had a higher total phenolic content and lower polyphenol oxidase and peroxidase activity. In addition, compared with the control, the treated fruits exhibited higher phenylalanine ammonia lyase, ascorbate peroxidase and superoxide dismutase activities; titratable acidity; and soluble solid, vitamin C and protein contents, indicating high fruit quality. Overall, sodium nitroprusside treatment at 200 μmol L−1 demonstrated the most positive preservation effects. Therefore, sodium nitroprusside treatment, particularly at 200 μmol L−1, can be used as an eco-friendly, safe and convenient method for postharvest quality management and high-efficiency preservation of rambutan fruits.

Chemometric Comparison and Classification of 22 Apple Genotypes Based on Texture Analysis and Physico-Chemical Quality Attributes

The large number of cultivars belonging to the cultivated apple (Malus × domestica Borkh.) reflects an extremely wide range of variability, including for fruit quality traits. To evaluate some characteristics of fruit quality, 22 apple genotypes were selected from a collection of germplasms containing more than 600 accessions, based on different considerations, including the use of fruits (dessert, cooking, processing, juice, cider, multipurpose). The mean water content of the studied apple genotypes was 85.05%, with a coefficient of variation (CV) of 2.74%; the mean ash content was 2.32% with a CV of 22.1%, and the mean total soluble solids was 16.22% with a CV of 17.78%, indicating a relatively small difference between genotypes for these indices. On the contrary, relatively large differences were registered between genotypes for fruit weight, volume, and titratable acidity with means of 119.52 g, 155 mL, and 0.55% malic acid, and CVs of 35.17%, 34.58%, and 54.3%, respectively. The results showed that peel hardness varied between 3.80 and 13.69 N, the toughness between 0.2 and 1.07 mm, the flesh hardness between 0.97 and 4.76 N, and the hardness work between 6.88 and 27.84 mJ. The current study can emphasize the possibility of choosing the appropriate apple cultivars to cross in the breeding process and how future strategies can help apple breeders select breeding parents, which are essential key steps when breeding new apple cultivars. In addition, multivariate analysis has proven to be a useful tool in assessing the relationships between Malus genetic resources.

Proximate Composition and Sensory Evaluation Between Artificially Ripened and Naturally Ripened Pineapples (Ananas comosus)

The number of artificially ripened pineapples is outnumbered than the naturally ripened pineapples. However, there is a lack of understanding between artificially ripened and naturally ripened pineapples. Thus the inquiry was anticipated to explore the physicochemical changes and organoleptic acceptability of the naturally ripened and artificially ripened pineapples. Farmers used different chemicals such as calcium carbide, ethylene, besides growth hormones to reduce production loss. Here we evaluated the content of moisture, ash, protein, fat, crude fiber, reducing sugar, total sugar, titratable acidity, sucrose, and vitamin C in both naturally ripened and artificially ripened pineapples. Artificially ripened pineapples showed a significantly lower vitamin C than naturally ripened ones, but arsenic content was nil in both samples. In the case of color and appearance, there was no significant difference between the two samples, but in case of the other organoleptic properties, such as flavor, sweetness, sourness, the natural one was more acceptable. Thus naturally ripened pineapples are more beneficial to consumers than artificially ripened ones.

Effect of Brine fermented Pickling to Physicochemical, Anti-nutritional, and Microbiological Attributes of Pickled gboma Eggplant (Solanum macrocarpon)

Gboma eggplant (Solanum macrocarpon) has low calorie, high phenolic and antioxidant, excellent dietary fibre and mineral content. Besides healthy effects, gboma eggplant also contained numerous anti-nutrients unbeneficial for human health. Due to high moisture content, gboma eggplant was highly perishable during post-harvest. This research observed the changes of nutritional proximate, mineral contents, acidification indexes, anti-nutrients, phytochemical and antioxidant properties, texture profiles, microbiological characteristics of both raw and pickled gboma eggplant. Gboma eggplant fruits were soaked in clean water for 2 minutes before cutting their calyx lobes. The pre-treated fruits were submerged in sterilized brine (5% salt) for 8 days. Periodically, pickled samples were taken to examine physicochemical, anti-nutritional, and microbiological attributes of pickled gboma eggplant. Results showed that nutritional proximate of moisture, ash, protein, fat, fibre, carbohydrate was varied slightly during fermentation. There was a decreasing trend of moisture and carbohydrate; meanwhile, there was an increasing trend of ash, protein, fibre during 8 days of fermentation. There was no significant difference of fat during pickling. There was a minor increment of mineral contents in all samples. There was accumulation of phenyllactic acid, ascorbic acid content and titratable acidity with exception of pH. Anti-nutrient contents like tannin, phytate, oxalate, steroidal glycoalkaloid greatly decreased in raw and pickled eggplant. Remarkable increments of total phenolic, flavonoid, DPPH free radical scavenging and FRAP ferric reducing antioxidant of raw and pickled eggplant was presented. Texture profiles of hardness, crispness, fracturability, crunchiness revealed a minor reduction of sensory scores during 8 days of fermentation. Lactic acid bacteria, Bacillus significantly proliferated; meanwhile, Micrococcus and S. aureus were absolutely retarded in pickled eggplant. Yeast and fungi increased in the first 4 days and decreased afterwards. There was no significant difference of proximate compositions; mineral contents; phenyllactic acid, ascorbic acid content, pH and titratable acidity; anti-nutritional contents; phytochemical and antioxidant properties; texture profile (sensory score); microbiological load (with exception of S. aureus) between pickled gloma eggplants at day 6th and day 8th of fermentation. At a quick glance, the length of fermentation could be shorted to 6 days instead of 8 days. However, at the 6th day, S. aureus load was still presented at 0.33±0.01 log CFU/g. The fermentation should be lasted to 8th day so that S. aureus load could be dropped down to zero to ensure microbial food safety. Raw gboma eggplant should be fermented in 8% brine solution for 8 days to obtain the best physicochemical, anti-nutritional, and microbiological properties of pickle. Findings of this research suggested that fermentation pickling would be an appropriate approach to improve nutritional, physicochemical and functional criteria while controlling toxic chemical residues, retarding the growth and proliferation of spoilage and pathogen microorganisms.

The Effect of Salinity on Fruit Quality and Yield of Cherry Tomatoes

Hydroponic cultivation of vegetables avoids problems with soil-borne plant pathogens and may allow higher yield. In arid climates and particularly on islands, high concentrations of sodium chloride can be present in the groundwater. For instance, in many sites of Malta, the groundwater contains more than 10 mM sodium chloride. Here we investigated the effects of sodium chloride at levels typically found in Malta on yield, physiology and fruit quality of tomato, the economically most important vegetable. We selected cherry tomatoes since their production is attractive due to their high marketing value. While the yield declined at higher salinity levels tested (17 and 34 mM), the quality increased significantly as indicated by higher total soluble solids and fructose and glucose levels. The type of substrate—coco peat, perlite or Rockwool—had only minor effects. Although the concentration of citric acid and malic acid remained unaffected, the pH dropped by approximately 0.1 unit and the titratable acidity increased slightly. This might be explained by a high uptake of chloride but a lower increase of the sodium content and a reduced potassium level in the fruits, shifting the equilibrium of the organic acids more to their protonated forms. Proline increased significantly, while the level of glutamic acid, which is crucial for the taste, remained unchanged. Our results show that cherry tomatoes can be cultivated in nutrient solutions prepared with salt-containing groundwater, as found in Malta. The yield declined to some extent but the quality of the produced fruits was higher compared to cultivation in salt-free media.

Evaluation of microbiological risks in cream as a raw material for buttermaking

The article presents the research results of studying the influence of various groups of microorganisms — coliform bacteria, lactic acid microorganisms, yeast, and spore bacteria — on the quality and storage capacity of cream used as a raw material for buttermaking. The objects of study were the following: cream as a raw material before and after pasteurization, as well as pasteurized cream seeded with testing cultures of various types of spoilage microorganisms. The samples were stored at temperature conditions of 30 ± 1 °C, 10 ± 1 °C, and 4 ± 2 °C. To evaluate the quality and storage capacity of cream used as a raw material, its microbiological and physicochemical indicators were determined by standardized methods: bacterial number, titratable acidity, indicators of oxidative spoilage of the fat phase. Organoleptic characteristics were evaluated in terms of taste, consistency and appearance. Research results have shown that the greatest microbiological risks during storage of cream used as a raw material are associated with lactococci, coliform bacteria and yeast. Microbiological risks caused by seeding of cream with thermophilic streptococcus, spore bacteria of the genus Bacillus and spore anaerobic microorganisms of the genus Clostridium are less significant, which is associated with the lack of development and metabolism of these groups of microorganisms at storage temperatures of 10 ± 1 °C and 4 ± 2 °C. At the same time, the reason for the rejection of cream contaminated with these testing cultures, at a storage temperature of 4 ± 2 °C, is primarily a decrease in organoleptic indicators, and at a temperature of 10 ± 1 °C — an excess in bacterial number.