Physicochemical and Microbiological Quality of Sous-Vide-Processed Carrots and Brussels Sprouts

Effect of different atmospheric and subatmospheric cooking techniques on physical and chemical qualitative properties of pork loin

In this paper, the effects of four cooking procedures were evaluated, two occurring in atmospheric (in ventilated and steam oven) and two in subatmospheric (vacuum and sous vide cooking) conditions on pork Longissimus lumborum. The main objective of the study was to compare and evaluate the physical and chemical characteristics. Samples were cooked in four independent trials namely Oven (O), Steaming (ST), Vacuum Cooking (VC) and Sous Vide (SV). The analyses included temperature, cooking effect, percentage weight loss, texture (cutting and double compression tests), colour (superficially and inside the sample), microstructure (optical microscopy) and fibres shortening analysis. To assess cooking effects on significant nutritional constituents, the fatty acid composition and the content of B vitamins were analysed. Volatile profiles of samples were also compared using solid-phase microextraction. SV cooking resulted in the less favourable meat texture, presenting the highest hardness and chewiness. Moreover, high hardness values measured on SV samples is also related to the high weight loss. The technique of oven cooking (O) demonstrated superior results in terms of mechanical properties, which are closely associated with the cooking values. Specifically, the cook value C0 was significantly higher in the case of oven cooking compared to SV, VC, and ST. Mild temperature conditions and cooking times of the four considered cooking techniques did not induce significant variations in the fatty acid composition and volatile profile. Conversely, SV and VC allowed the highest amount of vitamin B retention in cooked meat. This work suggests that some differences emerged on the effects due to sub-atmospheric and atmospheric cooking compared to traditional ones.

The Sous Vide Cooking of Mediterranean Mussel (Mytilus galloprovincialis): Safety and Quality Assessment

This study involves an investigation of the effects of various cooking temperatures, freeze-thaw processes, and food preservatives on the quality and shelf-life of sous vide Mediterranean mussels. Cooking temperatures of 80 °C or above significantly improved the microbiological quality, with bacterial counts remaining within the acceptability range for human consumption even after 21 days of refrigerated storage. Fast freezing followed by slow thawing preserved the highest moisture content, potentially improving texture. Sensory analysis revealed that refrigerated sous vide mussels maintained a comparable taste to freshly cooked samples. Frozen samples reheated via microwaving exhibited more intense flavour than pan-reheated or fresh mussels. Food additives, including citric acid, potassium benzoate, and potassium sorbate, alone or in combination with grape seed oil, significantly reduced total volatile basic nitrogen and thiobarbituric acid-reactive substances during 28 days of storage, indicating decreased spoilage and lipid oxidation. Mussels with a combination of these additives registered a nitrogen content as low as 22 mg of N/100g after 28 days, well below the limit of acceptability (<35 mg of N/100g). Food additives also inhibited bacterial growth, with mesophilic bacteria count below 3.35 Log CFU/g after 28 days, compared with 5.37 Log CFU/g in control samples. This study provides valuable insights for developing optimal cooking and preservation methods for sous vide cooked seafood, underscoring the need for further research on optimal cooking and freeze-thaw protocols for various seafood types.

Quality and Safety of Ready-to-Eat Golden Thistle (Scolymus hispanicus L.): A New Product for Traditional Italian Dishes

Golden thistle (Scolymus hispanicus L.) is a wild edible plant belonging to Asteraceae family, with a great potential for food applications. The aim of this study was to identify the best cooking procedure able to provide a high-quality, ready-to-use product. For this purpose, leaf midribs (the most used edible part of the plant) were cooked by boiling, steaming, and 'sous vide', and the cooked products were compared for their phenolic content and composition, antioxidant activity, sugar and inorganic ion content, organoleptic characteristics, and microbial safety, this latter also during storage. In general, boiling caused a decrease in the value of these parameters, despite being the best product for taste and overall acceptability. On the contrary, steaming and 'sous vide' resulted in the best treatments to preserve antioxidant activity, total phenols, and chlorogenic acid. In particular, in 'sous vide' cooked samples, a significant increase in the value of these parameters and a remarkable decrease in nitrate content were found. Moreover, 'sous vide' resulted in the best treatment also regarding microbial safety during shelf life; actually, after 15 days of storage at 8 °C, Enterobacteriaceae and mesophilic aerobic bacteria were not detectable in 'sous vide' samples. These results contributed to increase the knowledge of a wild edible plant with high nutritional properties and promoting its consumption by obtaining a ready-to-use product with good organoleptic characteristics and endowed with a long period of shelf life.

Fresh Basil Infusion: Effect of Sous-Vide Heat Treatment on Their Volatile Composition Profile, Sensory Profile, and Color

Herbs, including basil, are used to enhance the flavor of food products around the world. Its potential is influenced by the quality of fresh herbs and processing practices, wherein conditions of heat treatment play an important role. The aim of the research was to determine the effect of sous-vide heat treatment on the volatile compounds profile, sensory quality, and color of basil infusions. The material used for research was aqueous basil infusion prepared conventionally at 100 °C, and using the sous-vide method (65, 75, and 85 °C). The composition of volatile compounds was identified by GC/MS analysis, the sensory profile was assessed using a group of trained panelists, while the color was instrumentally assessed in the CIE Lab system. No significant differences were found in the intensity of the taste and aroma of basil infusions at different temperatures. Seventy headspace volatile compounds were identified in the analyzed samples, ten of which exceeded 2% of relative area percentage. The most abundant compounds were eucalyptol (27.1%), trans-ocimene (11.0%), β-linalool (9.2%), and β-myrcene (6.7%). Most of the identified compounds belonged to the terpenes and alcohols groups. Our findings show that the conventional herbal infusion was more like a sous-vide infusion prepared at the lowest temperature SV65, while SV75 and SV85 were similar to each other but different from the conventional. However, a smaller number of volatile compounds in the samples heated at higher temperatures of sous-vide were identified. The sous-vide samples showed a higher content of alkanes. The sous-vide method (p ≤ 0.05) resulted in darker, less green, and less yellow basil leaves than fresh and traditionally steeped ones. Long heat treatment under vacuum at higher temperatures causes a pronounced change in the aroma composition.

Effect of Heat Treatment by the Sous-Vide Method on the Quality of Poultry Meat

An increase in the consumption of poultry meat has been observed due to its availability, nutritional value, and delicate flavor. These characteristics make it possible to prepare, with the use of spices and other additives, many different dishes and products for increasingly demanding consumers. The sous-vide technique is increasingly being used to give new sensory attributes to dishes in gastronomy. The study aimed to assess the impact of the heat treatment method, i.e., the sous-vide method, as compared to traditional cooking, on the sensory quality of poultry meat, as well as the efficiency of the process with regard to technological quality. The cooking yield with the sous-vide method of processing poultry meat was higher than with the traditional method of cooking in water (88.5% vs. 71.0%, respectively). The meat was also found to be redder (a* = 254 vs. 074) and less yellow (b* = 1512 vs. 1649), as well as more tender. The sensory quality of chicken breast meat obtained by the sous-vide method was higher in terms of attributes such as color tone, tenderness, juiciness, and overall quality. At the same time, it was lower in terms of the odor of cooked meat and the flavor of cooked meat as compared to meat subjected to traditional cooking.

Effects of a High-Grain Diet With a Buffering Agent on Milk Protein Synthesis in Lactating Goats

Chinese dairy industries have developed rapidly, providing consumers with high-quality sources of nutrition. However, many problems have also appeared during the development process, especially the low quality of milk. To improve milk quality, a large amount of concentrated feed is usually added to the diet within a certain period of time, which increases the milk production to a certain extent. However, long-term feeding with high-concentration feed can lead to subacute rumen acidosis. Therefore, the present study aimed to determine the effect of adding a buffer on subacute rumen acidosis, and the improvement of milk production and milk quality. We also aimed to study the mechanism of promoting mammary gland lactation. A total of 12 healthy mid-lactating goats were randomly divided into two groups, they were high-grain diet group (Control) and buffering agent group. To understand the effects of high-grain diets with buffers on amino acids in jugular blood and the effects of amino acids on milk protein synthesis, Milk-Testing™ Milkoscan 4000, commercial kits, and high-performance liquid chromatography (HPLC) measurements were integrated with the milk protein rate, the amino acid concentration in jugular venous blood samples, quantitative real-time PCR, comparative proteomics, and western blotting to study differentially expressed proteins and amino acids in mammary gland tissues of goats fed high-grain diets. Feeding lactating goats with buffering agent increased the percentage of milk protein in milk, significantly increased the amino acid content of jugular blood (p < 0.05), and increase the amino acid transporter levels in the mammary gland. Compared with the high-grain group, 2-dimensional electrophoresis technology, matrix-assisted laser desorption/ionization-time of flight/time of flight proteomics analyzer, and western blot analysis further verified that the expression levels of beta casein (CSN2) and lactoferrin (LF) proteins in the mammary glands of lactating goats were higher when fed a high-grain diets and buffers. The mechanism of increased milk protein synthesis was demonstrated to be related to the activation of mammalian target of rapamycin (mTOR) pathway signals.

Impact of Mild Oven Cooking Treatments on Carotenoids and Tocopherols of Cheddar and Depurple Cauliflower (Brassica oleracea L. var. botrytis)

The effect of steam and sous-vide oven procedures on liposoluble antioxidants of colored cauliflower (orange and purple) was assessed for the first time and compared with domestic practice (boiling). In raw samples, the total carotenoid content was 10-fold higher in Cheddar than in Depurple (20.9 ± 2.1 vs. 2.3 ± 0.5 mg/kg dry weight), whereas the level of tocopherols was similar (28.5 ± 4.4 vs. 33 ± 5.2 mg/kg dry weight). The Cheddar liposoluble antioxidant matter contained violaxanthin, neoxanthin, α-carotene and δ-tocopherol, not detected in Depurple. All tests increased the bioactive compounds extractability with steam oven and sous-vide displaying similar effects, lower than boiling. In boiled Cheddar cauliflower, the total carotenoids and tocopherols contents increased with cooking time until they were 13-fold and 6-fold more than in raw cauliflower, respectively. Conversely, in the Depurple variety, contents increased by half with respect to the orange variety. However, from a nutritional point of view, no differences were revealed among the three different cooking treatments in terms of vitamin A and E levels expressed in μg/100 g of fresh vegetable because of the higher water content of boiled samples that must be considered when evaluating the effect of thermal treatment on cauliflower nutritional traits.

Sous-Vide as a Technique for Preparing Healthy and High-Quality Vegetable and Seafood Products

Sous-vide is a technique of cooking foods in vacuum bags under strictly controlled temperature, offering improved taste, texture and nutritional values along with extended shelf life as compared to the traditional cooking methods. In addition to other constituents, vegetables and seafood represent important sources of phytochemicals. Thus, by applying sous-vide technology, preservation of such foods can be prolonged with almost full retention of native quality. In this way, sous-vide processing meets customers' growing demand for the production of safer and healthier foods. Considering the industrial points of view, sous-vide technology has proven to be an adequate substitute for traditional cooking methods. Therefore, its application in various aspects of food production has been increasingly researched. Although sous-vide cooking of meats and vegetables is well explored, the challenges remain with seafoods due to the large differences in structure and quality of marine organisms. Cephalopods (e.g., squid, octopus, etc.) are of particular interest, as the changes of their muscular physical structure during processing have to be carefully considered. Based on all the above, this study summarizes the literature review on the recent sous-vide application on vegetable and seafood products in view of production of high-quality and safe foodstuffs.

Effects of different cooking methods on the antioxidant capacity and flavonoid, organic acid and mineral contents of Galega Kale (Brassica oleracea var. acephala cv. Galega)

Brassica spp. are good sources of bioactive substances, which are known to have beneficial health effects. The objective of this work was to evaluate the effect of different cooking methods (boiling, steaming, microwaving, pressure cooking and vacuum cooking) on the antioxidant capacity and on the flavonoid, organic acid and mineral contents of Galega kale. Results indicate that this vegetable has a high antioxidant capacity and high contents of total flavonoids, organic acids, and minerals such as potassium and calcium. All of the cooking methods yielded losses of antioxidant capacity and of total flavonoids, organic acids and minerals, relative to the contents in fresh kale. Steaming proved to be the best method of preserving the antioxidant capacity and bioactive compounds. Although cooking did not cause large losses of oxalic acid, the resulting oxalate:calcium ratio was rather low (<2). The present data demonstrate that the different cooking methods have different effects on the bioactive compounds in kale, and that it is important the optimisation of such methods in order to minimise losses of the nutritional properties.

Efficacy of Combined Sous Vide-Microwave Cooking for Foodborne Pathogen Inactivation in Ready-to-Eat Chicory Stems

There is a variety of different food processing methods, which can be used to prepare ready-to-eat foods. However, the need to preserve the freshness and nutritional qualities leads to the application of mild technologies which may be insufficient to inactivate microbial pathogens. In this work, fresh chicory stems were packed under a vacuum in films, which were transparent to microwaves. These were then exposed to microwaves for different periods of time. The application of sous vide microwave cooking (SV-MW, 900 W, 2450 MHz), controlled naturally occurring mesophilic aerobic bacteria, yeasts and molds for up to 30 d when vacuum-packed vegetables were stored at 4 °C. In addition, the process lethality of the SV-MW 90 s cooking was experimentally validated. This treatment led to 6.07 ± 0.7 and 4.92 ± 0.65 log cfu/g reduction of Escherichia coli and Listeria monocytogenes inoculated over the chicory stems (100 g), respectively. With an initial load of 9 log cfu/g for both pathogens, less than 10 cfu/g of surviving cells were found after 90 s cooking. This shows that short-time microwave cooking can be used to effectively pasteurize vacuum-packed chicory stems, achieving >5 log cfu/g reduction of E. coli and L. monocytogenes.

Potential use of microwave treatment on fresh-cut carrots: physical, chemical and microbiological aspects

BACKGROUND

The effect of microwave treatments (900 and 750 W for 45 and 60 s) on the microbial, physicochemical and sensory properties of fresh-cut carrot slices and the contents of several bioactive compounds was studied. Carrot samples were stored for 7 days at 5 °C.

RESULTS

The microwaving of fresh-cut carrots reduced the initial respiration rate (8.6 CO2 mL kg(-1) h(-1)) by 55-74% compared with untreated samples, although the rates then increased during storage. The initial pH (6.7), titratable acidity (0.036%), soluble solid content (8.2 °Brix) and shelf-life of the samples did not differ greatly from those of the untreated samples. Microwaving prevented the incipient whitening and surface dryness during storage. In general, no significant changes in phenylalanine ammonia lyase activity (5.5 µmol t-cinnamic acid kg(-1) h(-1)), total phenolics (TP, 81.3 mg chlorogenic acid equivalent kg(-1) fresh weight (FW)) or total antioxidant capacity (TAC, 74.2 µmol Trolox equivalent kg(-1) FW) were observed on the processing day or over storage. However, the mildest treatment (750 W for 45 s) caused TP and TAC enhancements of 118 and 394% respectively after 7 days of shelf-life. Microwave treatments reduced the initial microbial loads of the samples by up to 1.8 log units, although their microbial growth was greater than that of the untreated samples throughout storage.

CONCLUSION

Mild microwave treatments such as 750 W/45 s and 750 W/60 s are a good sustainable alternative to the use of NaOCl; however, combining them with other sanitizing techniques is needed to control microbial growth throughout the shelf-life of fresh-cut carrot slices.