Screening physicochemical,microbiological and bioactive properties of fruit vinegars produced from various raw materials

Food Science and Biotechnology - In the present study, variety of fruit vinegars were investigated in terms of their physicochemical, microbiological and bioactive properties. Total phenolic and...     

Osmotic dehydrofreezing of strawberries: Polyphenolic content, volatile profile and consumer acceptance

We evaluated dehydrofreezing in strawberries in terms of retention of healthy compounds (i.e. polyphenolics) and sensory qualities for direct consumption in substitution of fresh fruit. Different osmodehydration (OD at 30 °C and 5 °C), vacuum osmodehydration (VOD at 30 °C) and immersion chilling freezing (ICF) processes were applied in sucrose syrup. Samples were analyzed for dry matter, soluble solids, pH, titratable acidity, mass transfers, polyphenolic content by HPLC-DAD/MSD, volatile profile by SPME-GC/MSD and consumer acceptance. The results of sensory evaluation, in particular, confirmed the cryoprotective effects of osmotic processes of fruits with respect to untreated frozen control samples. The OD samples at 5 °C presented a water loss to solid gain ratio comparable to OD at 30 °C and VOD samples. Moreover, while osmo-dehydrofreezing at relatively high temperatures caused a slight depletion of phenolic compounds, the samples osmodehydrated at 5 °C showed higher polyphenolic retention. Data on aromatic compounds showed that some compounds increased (e.g. ethanol and acetaldehyde), while others did not appear to be affected by the pre-treatments.     

The effect of direct acidification on the microbiological,physicochemical and sensory properties of probiotic Minas Frescal cheese

Minas Frescal cheeses produced with the addition of the probiotic culture Bifidobacterium Bb‐12 and without (C1) or with (C2) lactic acid were evaluated in relation to the microbiological, physicochemical and sensory properties. After 28 days of storage, the cheeses without lactic acid showed lower moisture and pH, in addition to higher acidity and syneresis. This behaviour influenced the texture profile of the cheeses, making them harder and chewier. The colour attributes L* and b* diminished during the storage. The majority of the consumers classified the cheeses as having good acceptability and they would buy this type of functional food.     

Some physicochemical, microbiological, and sensory properties of tulum cheese produced from ewe's milk via a modified method

The purpose of this research was to investigate an alternative way to manufacture Erzincan tulum cheese in order to shorten production time and improve food safety. By adding 0.5% starter culture ( Streptococcus salivarius ssp. thermophilus and Lactobacillus delbrueckii ssp. bulgaricus cultures at a 1 : 1 ratio) to pasteurized ewe's milk (65°C for 30 min), the required time for manufacturing Erzincan tulum cheese was shortened from the traditional 10–12 days to 2 days. The cheeses manufactured with the modified method were ripened in three different packaging materials: goatskin, plastic, and ceramic. Physicochemical, microbiological, and sensory properties of the Erzincan tulum cheese were obtained during the ripening period at intervals of 2, 30, 60, and 90 days, and compared with those properties of samples manufactured by the traditional method. Significant microbiological and physicochemical differences were found between the modified samples and the traditional samples ( P <  0.01). However, the modified samples and the traditional samples were statistically similar in sensory properties to the exception of the modified sample packaged in plastic.     

Irradiated vacuum-packed lamb meat stored under refrigeration: Microbiology,physicochemical stability and sensory acceptance

Reducing spoilage and indicator bacteria is important for microbiological stability in meat and meat products. The objective was to evaluate the effect of different doses of gamma radiation on the shelf-life of lamb meat, vacuum-packed and stored under refrigeration, by assessing the microbiological safety, physicochemical stability and sensory quality. Lamb loin cuts (Longissimus dorsi) were irradiated with 1.5 kGy and 3.0 kGy. The samples, including control, were stored at 1 ± 1 °C during 56 days. Samples were analyzed on zero, 14, 28, 42 and 56 days by their microbiological and physicochemical characteristics. Sensory quality was carried out on day zero. The results showed a reduction (p < 0.05) in the microbial load of the irradiated samples. The acceptance of lamb loins was not affected (p > 0.05) by the radiation doses. Thus gamma irradiation at 3.0 kGy was effective in reducing the content of microorganisms, without harming the physicochemical characteristics evaluated.     

Effect of pressure and time on bioactive content,PPO inactivation,physicochemical and sensory properties of aonla (Emblica officinalis) juice during hydrodynamic cavitation processing

Food Science and Biotechnology - Physical and nutritional attributes of aonla juice treated with hydrodynamic cavitation (HC) at a pressure range of 5–15 psi and time between 5 to...     

A comparison between E-beam irradiation and high pressure treatment for cold-smoked salmon sanitation: microbiological aspects

The effectiveness of electron beam irradiation and high pressure treatment for the sanitation of cold-smoked salmon from two points of view, microbial safety and shelf-life extension, was compared. From the response of L. monocytogenes INIA H66a to irradiation, a D value of 0.51 kGy was calculated. For samples stored at 5 °C, 1.5 kGy would be sufficient to attain a Food Safety Objective (FSO) of 2 log₁₀cfu/g L. monocytogenes for a 35-day shelf-life, whereas 3 kGy would be needed in the case of a temperature abuse (5 °C + 8 °C). Pressurization at 450 MPa for 5 min was considered to be an insufficient treatment, since the FSO of 2 log₁₀cfu/g L. monocytogenes was only attained for a shelf-life of 21 days at 5 °C. However, treatment at 450 MPa for 10 min achieved this FSO for samples held during 35 days at 5 °C, or during 21 days under temperature abuse (5 °C + 8 °C) conditions. Irradiation at 2 kGy kept the microbial population of smoked salmon below 6 log₁₀cfu/g after 35 days at 5 °C, with negligible or very light changes in its odor. Pressurization at 450 MPa for 5 min also kept the microbial population below 6 log₁₀cfu/g after 35 days at 5 °C and did not alter odor, but affected negatively the visual aspect of smoked salmon.     

Stabilised cocosoy beverage: physicochemical and sensory properties

Beverages formulated from extracts of blanched coconut meat and germinated soybean were compared for their proximate composition to achieve the recommendations for vegetable milks. The stability of cocosoy beverage treated with varying levels (0.2–1.0%, v/v) of a 20% gum acacia solution was determined visually and objectively after 5 days of quiescent refrigerated storage. Cocosoy beverage (50:50, v/v coconut milk to soy milk) had 3.51% protein, 3.53% fat and 5.17% carbohydrate. Similarly, it contained 13.0, 5.2, 14.7, 18.7, 0.5 and 0.3 g kg⁻¹ K, Na, Ca, Mg, Fe and P, respectively. Compared with whole coconut milk and reconstituted whole milk powder, cocosoy beverage had significantly higher total solid contents and viscosity but lower pH and buffer index. A total solids top to bottom (T/B) ratio and protein (T/B ratio) of 0.97 and 1.0, respectively, corresponding to a separation index of 1.0, was obtained in cocosoy beverage stabilised with 1.0% gum acacia. Cocosoy beverage stabilised with 1.0% (v/v) gum acacia was rated significantly higher for all the tested sensory attributes. Cocosoy beverage, similar to whole coconut milk, had high contents of glucose and sucrose, a moderate content of fructose, low content of raffinose and no trace of stachyose. Copyright © 2006 Society of Chemical Industry     

Changes of physicochemical, microbiological, and textural properties during ripening of Italian low-acid sausages. Proteolysis, sensory and volatile profiles

In this study low-acid sausages were studied to characterize their physicochemical, microbiological, and textural properties during ripening. The final a(w) was 0.87-0.88, whereas pH values stayed around their initial values during processing. Lactic acid bacteria increased very slowly in number and a small increase of Micrococcaceae was also noticed. Low-acid sausages showed low hardness and cohesiveness, and were easily distinguishable by sensory analysis from other industrial and artisan sausages. Under the conditions of the study, observed volatile compounds were mainly from spices and wine. The respective contribution of muscle and indigenous bacterial enzymes to proteolysis was determined by comparing changes in low-acid sausages to those containing an antibiotic-antimycotic mixture or sugar. A large part of the degradation of myofibrillar proteins appeared due to endogenous enzymes, although bacterial proteinases contributed to the degradation of these proteins. The role of microorganisms in proteolysis was more evident in the degradation of sarcoplasmic proteins.     

Effect of saffron addition on the microbiological,physicochemical, antioxidant and sensory characteristics of yoghurt

The impact of added saffron on the characteristics of yoghurt was evaluated during storage. The fat content was lower in the saffron yoghurt. All colour variables were significantly affected by saffron and storage. From the 15th day of storage, bacterial numbers in the saffron yoghurt were higher than those of the control yoghurt. Sensory analysis data suggested that colour, odour and texture impacted consistently on the overall acceptability of the saffron yoghurt. Saffron addition significantly increased polyphenol content and antioxidant activity, providing evidence that the enrichment of natural yoghurt with saffron yields an innovative fermented product useful for supplementing antioxidant dietary intake.     

Influence of nano-ZnO on microbial growth,bioactive content and postharvest quality of strawberries during storage

A rapid decline of quality causes economic loss of strawberries after harvest. Treatments based on nano-ZnO at different concentrations (0.03%, 0.07% and 0.5%) were used to prolong the shelf-life of strawberry fruit in cold storage. After treatments microbial growth, weight loss, firmness, titratable acidity, soluble solid content, pH value, vitamin C, anthocyanin and total phenolics and antioxidant activity were evaluated at 0, 3, 6, 9, 12, 15 and 18 days of storage. Furthermore, the levels of zinc and the sensory attributes of treated strawberries were evaluated three days after treatment. Nano-ZnO treatments decreased the microbial load during fruit storage (total mesophilic bacteria in control and 0.5% nano-ZnO treated strawberries were 4.35 and 3.67 Log CFU g^− 1, respectively). Treatments delayed weight loss, retained fruit firmness and maintained anthocyanin, vitamin C, phenol content and antioxidant activity at higher concentration than those of untreated fruit. Fruit sweetness and aftertaste attributes were not affected by treatments but the 0.5% ZnO treated fruit was less luminous (1.6) compared to control (5.6). 0.5% nano-ZnO was the most effective in delaying changes in the ripening and reducing microbial populations among the treatments. These findings indicated that the nano-ZnO might provide an alternative to maintain quality and control decay of fresh strawberries during extended storage.Industrial relevanceStrawberries are a highly perishable fruit and postharvest life is limited to 4 days or even shorter at room temperature or 2 weeks at cold storage, therefore finding a method to extend the shelf life of strawberries is important. Modified atmosphere packaging is a useful method but control of spoilage microorganisms is still a problem. Fruit coating has great potential to extend fruit postharvest life and maintain nutritional quality. Nano-ZnO may be an effective alternative.     

Effect of Enterococcus faecium on microbiological,physicochemical and sensory characteristics of Greek Feta cheese

Greek Feta cheese was prepared using as adjunct starter cultures Enterococcus faecium FAIR-E 198, E. faecium FAIR-E 243, and their combination. Numbers of enterococci in the control and in the batches containing E. faecium strains as adjunct starters rapidly increased until day 15 of ripening, and then remained constant. Both E. faecium strains positively affected the counts of non-starter lactic acid bacteria (NSLAB), micrococci and coliforms, while thermophilic cocci were not influenced. Moreover. E. faecium FAIR-E 243 enhanced the growth of mesophilic cocci and thermophilic bacilli. Physicochemical characteristics, such as pH, moisture, ash, salt in moisture and fat in dry matter (FDM) were not influenced by the addition of the E. faecium strains. The most pronounced effect was observed in the case of proteolysis. Both E. faecium strains, either as sole adjunct starter or in combination, increased the proteolytic index and the free amino groups concentration, and enhanced degradation of alpha(s1)- and beta-caseins in comparison to the control. Furthermore, the reverse-phase (RP)-HPLC peptide profiles of the water-soluble nitrogen (WSN) fractions were significantly affected by the addition of enterococci. The main volatile compounds produced were ethanol, acetate, acetone, acetaldehyde, acetoin and diacetyl, with highest amounts determined for ethanol, followed by acetate. Both E. faecium strains positively affected taste, aroma, colour and structure of the full-ripened cheeses, as well as the overall sensory profile. The present work emphasizes the technological significance of E. faecium strains and supports their use as adjunct cultures in the manufacture of Feta cheese.