Use of natural compounds to improve the microbial stability of Amaranth-based homemade fresh pasta

A study on the use of natural antimicrobial compounds to improve the microbiological stability of refrigerated amaranth-based homemade fresh pasta is presented in this work. In particular, the antimicrobial activity of thymol, lemon extract, chitosan and grapefruit seed extract (GFSE) has been tested against mesophilic and psychrotrophic bacteria, total coliforms, Staphylococcus spp., yeasts and moulds. A sensory analysis on both fresh and cooked pasta was also run. Results suggest that chitosan and GFSE strongly increase the microbial acceptability limit of the investigated spoilage microorganisms, being the former the most effective. Thymol efficiently reduces the growth of mesophilic bacteria, psychrotrophic bacteria and Staphylococcus spp., whereas it does not affect, substantially, the growth cycle of total coliforms. Lemon extract is the less effective in preventing microbial growth. In fact, it is able to delay only total mesophilic and psychrotrophic bacterial evolution. From a sensorial point of view no significant differences were recorded between the control samples and all the types of loaded amaranth-based pasta.     

Growth of Listeria monocytogenes in egg salad and pasta salad formulated with mayonnaise of various pH and stored at refrigerated and abuse temperatures

This study investigated and modeled the behavior of Listeria monocytogenes in egg salad and pasta salad as affected by mayonnaise pH (3.8, 4.2, 4.6, and 5.0) and storage temperature (4, 8, and 12 degrees C). At each storage temperature, L. monocytogenes was able to grow in both salads regardless of the mayonnaise pH. The lag-phase durations (LPD) of L. monocytogenes in egg salad ranged from 33 to 85, 15 to 50, and 0 to 19 h, and the growth rates (GR) ranged from 0.0187 to 0.0318, 0.0387 to 0.0512, and 0.0694 to 0.1003 log(10)cfu/h at 4, 8, and 12 degrees C, respectively. The LPD of L. monocytogenes in pasta salad ranged from 210 to 430, 49 to 131, and 21 to 103 h, and GR ranged from 0.0118 to 0.0350, 0.0153 to 0.0418, and 0.0453 to 0.0718 log(10)cfu/h at 4, 8, and 12 degrees C, respectively. The growth of L. monocytogenes was more rapid in egg salad than in pasta salad, indicating that a better growth environment for L. monocytogenes existed in egg salad. In both salads, the LPD decreased and the GR increased as the storage temperature increased. Mathematical models and response surface plots describing the LPD and GR of L. monocytogenes in both salads as affected by the mayonnaise pH and storage temperature were developed. The models confirmed that the growth of L. monocytogenes in egg salad and pasta salad was primarily promoted by higher storage temperatures and, secondarily, by higher mayonnaise pH. The conditions under which the models may be applied to estimate the growth of L. monocytogenes in both salads were identified.     

Effect of inulin soluble dietary fibre addition on technological, sensory, and structural properties of durum wheat spaghetti

Investigation of two inulins with differing degrees of polymerisation and crystallinity demonstrated different levels of integration with the starch-gluten matrix during pasta preparation. The impact of higher molecular weight inulin incorporation on technological and sensory properties was minimal, with deterioration in properties becoming significant only at 20% incorporation, while lower molecular weight had a greater negative impact on pasta firmness, cooking loss, and sensory acceptability. In vitro starch digestion of pasta was reduced with up to 5% addition of inulin of degree of polymerisation 12-14 (FH-D), but increased with high levels of addition. These effects were not observed in inulin with a degree of polymerisation of 7-8 (LV-100). Microscopy showed the starch granules were apparently encapsulated by a protective coat of inulin FH-D, but at 20% a disruption to the matrix was evident. For inulin FH-D, XRD analysis of digested pasta found a maximum crystallinity which coincided with the maximum reduction in starch hydrolysis, suggesting that a stronger gluten matrix enhanced by added inulin is indeed structurally different at the nanometre level.     

Chemical composition, cooking quality, and consumer acceptance of pasta made with dried amaranth leaves flour

Pasta is a staple food in many countries. Amaranth is a pseudo-cereal being re-discovered because of its nutritional properties. The main objective of this study was to evaluate the potential of the green material of the amaranth plant (leaves) as a component for pasta production and its effect on the pasta quality and consumer acceptance. Dried amaranth (Amaranthus caudatus) leaves and spinach leaves flours were prepared. Pasta samples were manufactured following a small-scale pilot procedure. Amaranth pasta samples were evaluated for its chemical composition, cooking quality, textural, and sensory/consumer acceptance. Results showed that pasta made with dried amaranth leaves had similar chemical composition (protein content: 14.18 g/100 g, Fe content: 9.1 mg/100 g), cooking quality (2.15 pasta weight increase, 4.47% residue loss), textural characteristics (firmness and adhesiveness), and sensory acceptance than green pasta made with dried spinach leaves. Since amaranth leaves have similar nutritional characteristics to spinach leaves and since this biomass in not currently used for food purposes, this study points out that amaranth leaves could be technically used for pasta production and that consumer acceptance of pasta made with amaranth green leaves flour is similar to that of pasta made with spinach.     

Growth capacity of Listeria monocytogenes in ingredients of ready-to-eat salads

Raw minimally processed vegetables and fruits as well as boiled pasta and potato are the main ingredients of ready-to-eat (RTE) salads. These ingredients are diverse in their ability to support growth of Listeria monocytogenes. The objective of this study was to determine to what extent different ingredients can contribute to growth of L. monocytogenes in RTE salads. This was done by assessing the growth capacity of L. monocytogenes in ingredients of RTE salads by means of challenge tests and determination of the effect of product characteristics and presence of competitive flora. The majority of the tested products did not support or hardly supported growth of L. monocytogenes. The calculated maximum increase of 3.4 log CFU/g was exceeded in Galia melon, potato and pasta products. In RTE dinner salads, growth of L. monocytogenes was supported by the carbohydrate component. Galia melon, which is often used as ingredient of fruit salads, can contribute to growth of L. monocytogenes in these products. Growth inhibition, or differences in relative increase, could not always be explained by a_w, pH or presence of competitive flora. The effect of competitive flora, especially lactic acid bacteria, on growth inhibition was observed in non-pasteurized potato, white cabbage and mango.     

Effect of insoluble dietary fibre addition on technological,sensory, and structural properties of durum wheat spaghetti

Insoluble fibres are important in human health and disease prevention and can be incorporated into food. High fibre pasta prepared with bran is typically inferior quality compared to durum pasta. This study compared spaghetti prepared from durum semolina substituted with various amounts of either durum bran or germ (pollard) dried at high temperature. Pasta was evaluated for cooking properties, texture, sensory, fibre content, antioxidant status (AO) and in vitro starch digestibility to determine the dose producing acceptable quality. Pollard at 10% substitution had minimal impact on quality with higher AO and fibre. Above 30%, pasta had undesirable colour, sensory properties and higher starch digestion. Although bran substituted pasta had undesirable sensory and technological properties, especially at 30% incorporation, it does provide more dietary fibre and antioxidants than regular pasta and does not affect starch digestibility. Interestingly, a significant amount of AO was retained in the cooked pasta. The study illustrates the value of structural analysis to explain observed technological properties of the product with fibre inclusion.     

Prediction of pasta drying process based on a thermogravimetric analysis

The drying process of durum wheat semolina dough was measured by thermogravimetry in the temperature and relative humidity ranges of 30–90 °C and 0–80%, respectively, in order to predict the drying process of pasta under any drying conditions. About 20% of the water was evaporated during the constant drying-rate period which has been ignored in previous studies. It is demonstrated that the constant drying-rate period should be taken into account in order to predict the drying curve with a high accuracy. The drying rate during the constant drying-rate period and the mass transfer coefficient estimated by the thermogravimetric analysis were expressed as functions of the temperature and relative humidity, and they were useful for predicting the drying processes of pasta under any drying conditions including the programmed ones.     

Toxin producing Bacillus cereus persist in ready-to-reheat spaghetti Bolognese mainly in vegetative state

The potential of Bacillus cereus to cause a diarrheal toxico-infection is related to its ability to perform de novo enterotoxin production in the small intestine. A prerequisite for this is presence of sufficient numbers of B. cereus that have survived gastro-intestinal passage. It is known that the percentage of survival is much smaller for vegetative cells in comparison to spores and it is therefore important to know the state in which B. cereus is ingested. The results of the current study performed on twelve B. cereus strains, comprising both diarrheal and emetic type, indicate that exposure via contaminated foods mainly concerns vegetative cells. Inoculated vegetative cells grew to high counts, with the growth dynamic depending on the storage temperature. At 28 °C growth to high counts resulted in spore formation, in general, after 1 day of storage. One strain was an exception, producing spores only after 16 days. At 12 °C obtained high counts did not result in spore formation for 11 of 12 tested strains after two weeks of storage. The highest counts and time to sporulation were different between strains, but no difference was observed on the group level of diarrheal and emetic strains. The spore counts were always lower than vegetative cell counts and occurred only when food was obviously sensory spoiled (visual and odor evaluation). Similar observations were made with food inoculated with B. cereus spores instead of vegetative cells. Although the prospect of consuming spores was found very weak, the numbers of vegetative B. cereus cells were high enough, without obvious sensory deviation, to survive in sufficient level to cause diarrheal toxico-infection.     

Furosine and flavour compounds in durum wheat pasta produced under different manufacturing conditions: Multivariate chemometric characterization

The headspace solid-phase microextraction (HS-SPME) technique followed by GC/MS analysis was performed to evaluate the volatile fraction of durum wheat pasta produced under different process conditions (artisan manufacturing methods or industrial processes). At the same time, HPLC analysis was performed to quantify furosine in the same pasta samples. Furosine is commonly used as an index of nutritional damage occurring during pasta drying, although drastic thermal treatments may lead to its underestimation. Moreover, since furosine determination requires time/solvent-consuming methods, a more convenient approach could be the identification of volatile compounds formed during the drying step and detectable through simple and automated methods. Principal Component Analysis (PCA) was applied to experimental data in order to discriminate pasta samples according to their drying conditions. A limited number of volatile compounds including Maillard reaction and lipid-derived products (nonanal, hexanal, nonanoic acid, maltol and 2-furanmethanol) proved to be crucial in the differentiation of the samples. Therefore, these compounds could be used as pasta quality markers, alternatively to furosine, or as process markers to keep the drying treatment under control.