Influence of storage and preservation on microbiological quality of silo ovine milk

This study was designed to analyze the effects of the storage and preservation conditions on counts of mesophilic, thermoduric, psychotrophic, coliform, Escherichia coli, Streptococcus agalactiae, and Staphylococcus aureus organisms in silo ovine milk. A total of 910 analytical determinations were conducted from aliquots of 10 silo ovine milks. The conditions tested were unpreserved and azidiol-preserved milk stored at 4°C, and unpreserved milk stored at −20°C. Milk aged 2, 24, 48, 72, and 96 h post-collection for refrigerated aliquots, and 7, 15, and 30 d post-collection for frozen aliquots. The factors silo and storage conditions significantly contributed to variation of all microbiological variables, although milk age effect within storage was only significant for mesophilic, psychrotrophic, and coliform bacteria counts. In refrigerated raw milk, mesophile, psychrotroph, and coliform counts significantly increased over 96 h post-collection, whereas the other groups and bacteria species tested maintained their initial concentration. In all cases, azidiol preservation maintained the initial bacterial concentration in raw sheep milk under refrigeration throughout 96 h. Thus, azidiol was a suitable preservative for microbiological studies in sheep milk. Smallest counts were registered for frozen samples, particularly for coliforms, E. coli, Strep. agalactiae and Staph. aureus. Estimates of mesophilic, thermoduric and psychrotrophic organisms showed similar values on both azidiol-preserved and frozen milk samples. Coliforms and E. coli counts significantly decrease over time after freezing. Consequently, freezing at −20°C could also be appropriate for analysis of mesophilic, thermoduric, and psychrotrophic bacterial groups, but not for coliforms or mammary pathogens.     

Sensory,microbiological and chemical assessment of the freshness of red mullet (Mullus barbatus) and goldband goatfish (Upeneus moluccensis) during storage in ice

The shelf life of red mullet and goldband goatfish during ice storage were studied in terms of sensory, microbiological and chemical changes. The sensory acceptability limit was 8 days for goldband goatfish (Upeneus moluccensis) and 11 days for red mullet (Mullus barbatus) stored in ice. The TVC level was correlated with sensory assessment. The TVC exceeded 7 log cfu g⁻¹ after 8 days for goldband goatfish, and 11 days for red mullet. At the end of storage period, pH, TVB-N, TBA, FFA and PV for red mullet were 7.84, 47.19 mg/100 g, 0.69 mg MA kg⁻¹, 1.17% oleic acid and 1.58 meq O₂/kg and for goldband goatfish they were 7.53, 43.97 mg/100 g, 0.74 mg MA kg⁻¹, 1.62% oleic acid and 1.68 meq O₂/kg, respectively. In red mullet, agmatine, serotonin, histamine and dopamine became the dominant amines, reaching 7.30, 5.97, 2.52 and 2.31 mg/100 g, respectively. Also the dominant amines for goldband goatfish were 4.37, 3.88, 3.38 and 2.00 mg/100 g for histamine, agmatine, dopamine and putrescine, respectively.     

The inhibitory potential of feed supplementation with rosemary and/or α-tocopheryl acetate on microbial growth and lipid oxidation of turkey breast during refrigerated storage

Twenty-four 12-week-old female turkeys divided into four equal groups were fed a basal diet (CONT) or basal diet supplemented with 300 mg α-tocopheryl acetate/kg (TOC), or 5 g rosemary/kg (ROS5), or 10 g rosemary/kg (ROS10), for 4 weeks. Following slaughter, fillets from breast were stored at 4 °C in the dark for 12 days, and lipid oxidation was assessed on the basis of the malondialdehyde formed, whereas microbial growth on the basis of total viable counts (TVC), lactic acid bacteria (LAB), Enterobacteriaceae (ENB) and psychrotrophic (PSY) bacteria. Results showed that incorporation of dried rosemary in turkey diets delayed lipid oxidation in raw breast meat during refrigerated storage. Dietary rosemary at the level of 1 g/100 g was significantly (P<0.05) more effective in delaying lipid oxidation compared to 0.5 g/100 g but inferior to the dietary supplementation of 300 mg α-tocopheryl acetate/kg. TVC, LAB, ENB and PSY bacterial counts were all significantly increased (P<0.05) in breast samples of all groups throughout the refrigerated storage. The TOC and CONT groups presented TVC, LAB, ENB and PSY counts that did not differ (P>0.05) among each other, during the whole storage period. However, the rosemary-supplemented groups presented bacterial counts that were significantly lower (P<0.05) than the CONT and TOC groups, at day 2 of storage period and thereafter. During this period, the ROS5 group presented TVC, LAB, ENB and PSY counts that were significantly higher (P<0.05) than the ROS10 group.     

Chemical,microbiological and sensory changes of dried Acetes chinensis during accelerated storage

Chemical, microbiological and sensory changes of dried Acetes chinensis during 28 days of accelerated storage at 37 °C were studied. Eighty volatile components including alcohols, aldehydes, acids, ketones, esters, alkanes, nitrogen-containing components, aromatic components and terpenes were identified by headspace sampling and gas chromatography–mass spectrometry (GC–MS) method during storage. Among these volatile components, the relative content of trimethylamine was the highest during storage, which increased from 11.36 ± 1.02% at day 0 to 14.60 ± 0.58% at day 28. Values of total volatile base nitrogen (TVB-N), trimethylamine (TMA), thiobarturic acid reactive substances (TBARS), total viable mesophilic count (TVC) and sensory characteristics of colour and odour for dried A. chinensis changed significantly during storage. Volatile components, TVB-N, TMA, pH, TBARS, TVC, colour and odour characteristics at different storage time were statistically interpreted by principle component analysis (PCA) method in order to found the main indices for the freshness of dried A. chinensis. The results suggested that colour, TMA, TVB-N, TBARS, odour, TVC and some volatile components could reflect the quality changes perfectly.     

Shelf-life extension of crucian carp (Carassius auratus) using natural preservatives during chilled storage

The effect of the natural preservatives, tea polyphenols and rosemary extract, on microbiological [total viable count (TVC)], chemical [pH, total volatile base nitrogen (TVB-N), K-value and thiobarbituric acid (TBA) values], texture and sensory changes of air-packaged whole crucian carp (Carassius auratus) stored at 4 ± 1 °C was investigated for 20 days. The shelf-life of crucian carp was found to be 7–8 days for untreated group (control), 13–14 days for tea polyphenols group and 15–16 days for rosemary extract treated group according to sensory assessment results, for which the corresponding microbiological assessment also showed an increased shelf-life. Meanwhile, the increases of pH, TVB-N, K-value and TBA values were significantly delayed in both treated groups of samples compared to the control group. Thus, either tea polyphenols or rosemary extract could be used as potential preservatives to extend the shelf-life of crucian carp during chilled storage.     

Chemical and sensory quality changes of fish fingers,made from mirror carp (Cyprinus carpio L., 1758), during frozen storage (−18 °C)

The effects of frozen storage at −18 °C on the chemical and sensory qualities of fish fingers produced from unwashed and washed mirror carp (Cyprinus carpio) mince were investigated. The amounts of moisture, crude protein, lipid, crude ash, ω3 polyunsaturated fatty acids (PUFA ω3), and ω6 polyunsaturated fatty acids (PUFA ω6) in fish fingers produced from unwashed mince (UWF) were found to be 68.50%, 15.5%, 6.00%, 2.20% 2.31%, and 55.2%, respectively, while they were found to be 70.23%, 10.8%, 2.14%, 1.80%, 2.28%, and 54.6%, respectively, in carp fingers produced from washed mince (WF). The thiobarbituric acid value (TBA, mg malonaldehyde/kg) was found to be significantly higher in mince of WF than in mince of UWF and increased significantly during frozen storage in both the mince of UWF and WF (p < 0.05). A significant decrease in pH was obtained throughout the washing treatment (p < 0.05). There were no significant differences of pH in either the mince of UWF or WF between the beginning and end of the storage periods (p > 0.05), whereas a sharp increase was observed in the fourth month in both groups. The protein solubilities of the mince of both UWF and WF decreased significantly throughout the storage periods (p < 0.05). Sensory parameters of colour, odour, flavour, and general acceptability for both groups decreased during the frozen storage period (p < 0.05) but were still within acceptable limits. It was also concluded that mirror carp was a good source for fish fingers and that product could be stored for five months in a frozen state without undesirable changes of sensory and chemical qualities.     

Effect of delayed icing on quality changes of iced rainbow trout (Onchorynchus mykiss)

The effect of delayed icing on quality deterioration of rainbow trout (Onchorynchus mykiss) iced 0, 4 and 8 h after catch was assessed by chemical, microbiological and sensory methods. Total volatile basic nitrogen (TVB-N), free fatty acids (FFA), peroxide value (PV) and thiobarbituric acid (TBA) values increased during the pre-icing duration. Delayed icing led to significant increased (p < 0.05) in total viable counts (TVC) throughout the period of storage. This study showed that sensory analysis of rainbow trout correlated well with microbiological analysis. Results of this study according microbiological and sensory data indicated that the shelf-life of rainbow trout stored in ice immediately after catch was approximately 9–11 days, while delay in icing for 4 and 8 h shortened the shelf-life was around 5–7 and 1–3 days, respectively.     

Effect of frozen storage conditions (temperature and length of storage) on microbiological and sensory quality of rustic crossbred beef at different states of ageing

The effect of frozen storage conditions on meat from 36 Morucha × Charolais crossbred yearlings was studied. Slices of M. Longissimus thoracis were randomly assigned to groups arising from the combination of experimental factors. These factors were: ageing extent (3 and 10 days), length of frozen storage (0, 30, 75 and 90 days) and temperature (−20 and −80 °C). Regarding microbiological counts, although values were acceptable in all cases, longer storage time and longer previous ageing extent provided higher phychrotrophic bacteria counts. As frozen storage period increased, colorimetric parameters L^∗, a^∗ and C^∗ decreased, but H^∗ increased. Regarding Warner–Braztler shear force and tenderness values, an interaction (p < 0.05) between frozen storage and post-mortem ageing resulted from larger differences between frozen storage periods at shorter ageing periods than those at longer ageing periods. Frozen storage for 90 days resulted in a reduction in water holding capacity, without differences in juiciness. No effect of freezing temperature was observed in any of the parameters studied.     

EFFECT OF PRESERVATION METHODS ON QUALITIES OF GIANT FRESHWATER PRAWNS (MACROBRACHIUM ROSENBERGII)

The effects of three common commercially-practiced preservation methods, i.e., individual quick freezing (IQF), freeze drying and canning, on the quality of giant freshwater prawns (Macrobrachium rosenbergii) were studied. Physical and chemical quality parameters of IQF prawns stored at ?25 ± 1C changed slightly during 6 months' storage. The freeze-dried and the canned prawns stored at 24 ± 0.5 C could maintain their physical, chemical and sensory qualities during 6 months of storage very well.     

Effect of freezing method and frozen storage duration on lamb sensory quality

This study assessed the effect of three freezing methods with three frozen storage durations (1, 3, and 6 months) on the sensory quality of lamb. Methods were: air blast freezer, freezing tunnel + air blast freezer, and nitrogen chamber + air blast freezer. Meat was frozen after 48 h of ageing (0-4 °C). Fresh meat (72 h ageing at 2-4 °C) was used as control. Sensory analyses (trained panel and consumer tests) were performed on loin chops (Longissimus lumborum) after 24 h of thawing. Results from the trained panel test showed that freezing (method and/or storage duration) had no significant effect. Consumers found that freezing affected sensory quality. Cluster analysis for overall acceptability divided the population into four classes with different preference patterns, and none of them showed a significant preference for fresh meat. The small differences between fresh and thawed meat shown in this study should not give consumers concerns about buying frozen meat or consuming thawed meat.     

Nucleotide degradation and biogenic amine formation of wild white grouper (Epinephelus aeneus) stored in ice and at chill temperature (4 °C)

Sensory (cooked and uncooked), chemical (proximate composition, TVB-N, nucleotide degradation products and biogenic amines) and microbiological quality (TVC and total coliform) changes were investigated during storage of ungutted white grouper kept in ice and at chill temperature (4 °C). According to the sensory assessment, the shelf life of white grouper was 16 days in ice and 4 days for fish stored at chill temperature. TVB-N values increased with storage time. Amines found in white grouper stored in ice were TMA, putrescine, cadaverine, 2-phenylethylamine, dopamine, agmatine, tryptamine and serotonin. Histamine, spermine, spermidine were never detected with either storage condition. The acceptability limit in terms of microbial count was exceeded at 8 days in ice and at 4 days for fish stored at chill temperature. Total coliform count was 2.8 log₁₀ cfu/ml at 1 day and reached 10⁵ cfu/ml for both storage conditions.     

Influence of the frozen storage on some characteristics of ripened Manchego-type cheese manufactured with a powdered vegetable coagulant and rennet

A study was made of the effect of freezing and nine months’ frozen storage on the chemical, microbiological and sensorial characteristics of fully ripened Manchego-type cheese. Chemical components, water activity and nitrogen compounds were not altered by freezing and frozen storage. Soluble and non-protein nitrogen were significantly higher in cheeses produced with the powdered vegetable coagulant (PVC) compared to those made with rennet. Proteolysis continued slowly during frozen storage, with higher amino acid and ammonia nitrogen rates at the end of the storage period. Micrococci (P-value <0.05, in cheese made with PVC) and staphylococci counts tended to decrease during frozen storage; however total viable, lactic acid bacteria and mold-yeasts counts were similar throughout the nine months. Changes in sensorial parameters were observed (P-value <0.05) throughout freezing and frozen storage, affecting the creaminess of cheeses made with chymosin and the taste intensity and salty taste of cheese obtained with vegetable coagulant. Cheeses obtained with PVC proved to have a more acid taste and greater taste intensity (P < 0.01) as well as displaying a more bitter taste, greater creaminess and lower degree of hardness (P-value <0.001) than those produced with rennet.     

Textural Attributes of Mechanically and Cryogenically Frozen Whole Crayfish (Procambarus clarkii)

Textural quality of quick frozen and conventionally frozen whole crayfish was evaluated. Toughness, as measured by Kramer shear press, increased significantly (p≤ 0.05) as a result of freezing. Between 6 and 16 wk of frozen storage, toughness increased (p≤ 0.05) in seasoned (SCF) samples but remained the same in all other treatments. In all treatments, toughness declined after 16 wk of frozen storage. Individually quick frozen (IQF) samples were more tender (p≤ 0.05) than conventionally frozen (CF) samples. Seasoned crayfish had the greatest degree of toughness (p≤ 0.05). Extractable protein decreased (p≤ 0.05) during frozen storage, with IQF samples showing the smallest changes. SCF samples had significantly ( p ≤ 0.05) lower moisture retention and more (p≤ 0.05) lipid oxidation.     

Changes in qualities of minimally processed litchis: Effect of antibrowning agents, osmo-vacuum drying and moderate vacuum packaging

Litchi fruits (litchis) are highly susceptible to pericarp browning which lowers their commercial value even though the edible portion (aril) remains in excellent condition. Therefore, minimal processing of litchis was carried out. Litchis were peeled, destoned, and arils were treated with antibrowning agents (4.9 g/kg cysteine, 20 g/kg ascorbic acid and 0.134 g/kg 4-hexyl resorcinol) along with osmo-vacuum dehydration (OVD) (502 g/kg sucrose syrup for 10 min at 570 mmHg vacuum followed by a relaxation of 10 min at atmospheric pressure) and stored at 4±2 °C. The samples were analyzed for physicochemical, sensory and microbiological qualities during storage. Changes were found to become significant (P?0.05) after 4 days of storage. During storage for 24 days, a decrease in pH, TSS (°brix), sugars (g/kg), ascorbic acid (g/kg), total phenolics (g/kg), firmness (N), color (L^* value) and sensory characteristics was observed whereas an increase in microbial counts (log cfu/g), acidity (g/kg) and drip losses (ml/kg) was observed. The combined treatment of litchis with antibrowning agents and osmo-vacuum dehydration treatment were found to be most effective in preventing the changes and the samples were acceptable (sensory score >7.0) upto 24 days, whereas the samples given only OVD treatment lost acceptability due to poor color after 16 days as compared to 8 days for the control samples (dipped in water for 10 min) during refrigerated storage.     

The effect of liquid smoking of fillets of trout (Salmo gairdnerii) on sensory,microbiological and chemical changes during chilled storage

The storage time at 4 ± 1 °C of liquid smoked fillets of trout (Salmo gairdnerii) produced with a new smoking technique, using a combination of liquid smoke and steaming at 2 bar pressure for 30, 45 and 60 min, was studied. Maximum total viable counts (TVC) were reached after 25 days in the samples processed for 30 min and after 48 days in those processed for 45 and 60 min. However, panellists rejected the samples long after maximum TVC was observed. The increase of TVC was also confirmed using a particle size analyser, indicating a possible direct detection of microbial growth. A reduction of about 50% in the C22:6n − 3/C16:0 ratio was found across the whole period of storage, indicating lipid oxidation. The hypoxanthine/inosine (Hx/Ino) ratio showed a good relationship with both TVC and sensory results. Thus, when the Hx/Ino ratio was higher than 1.3, the products had reached their maximum acceptable TVC and were approaching their rejection time by the panellists, indicating that the Hx/Ino ratio is a good indicator of the shelf-life of smoked products of trout (S. gairdnerii).     

Effects of refrigeration,freezing and replacement of milk fat by inulin and whey protein concentrate on texture profile and sensory acceptance of synbiotic guava mousses

The effects of refrigeration, freezing and substitution of milk fat by inulin and whey protein concentrate (WPC) on the texture and sensory features of synbiotic guava mousses supplemented with the probiotic, Lactobacillus acidophilus La-5, and the prebiotic fibre oligofructose, were studied. The frozen storage (−18 ± 1 °C), followed by thawing at 4 °C before the analyses, and the complete replacement of the milk fat by inulin plus WPC, led to significant differences in the instrumental texture parameters of mousses (P < 0.05). Nonetheless, these changes did not affect the sensory acceptability of the products studied. The frozen storage may be employed to extend the shelf-life of synbiotic guava mousses. Additionally, to obtain a texture profile similar to the traditional product, the simultaneous addition of inulin and WPC is recommended only for the partial replacement of milk fat in refrigerated and frozen mousses, and the total proportion of both ingredients together should not exceed 2.6%.     

Impact of postharvest treatments,chlorine and ozone,coupled with low-temperature frozen storage on the antimicrobial quality of lowbush blueberries (Vaccinium angustifolium)

The additive antimicrobial influence of low-temperature frozen storage and oxidation treatments was investigated using 100 mg/L chlorine or 1 mg/L aqueous ozone sprays applied to lowbush blueberries (Vaccinium angustifolium) destined for individually quick frozen (IQF) markets. Following a 60 s contact time with either oxidant, treated berries were blast frozen at ?30 °C and stored at ?18 ± 2 °C for up to 12 months. Significant differences (p ≤ 0.05) between treatment effectiveness at time 0 were not observed among all populations evaluated (mesophilic bacteria, yeast, and mold), although ozone treatments resulted in the greatest log reductions in each population. In contrast, after 12-months of frozen storage, the greatest microbial reductions in all populations were observed on chlorine-treated berries. Results suggest a significant impact (p ≤ 0.05) of low-temperature frozen storage on microbial counts of both treated and non-treated blueberries yet, chlorine-treated berries stored for up to 12 months exhibited significantly greater reductions (p ≤ 0.05) in bacterial and yeast counts compared to non-treated controls and ozone-treated berries. Study results suggest an additive effect between freezing and chlorine pre-treatments in altering microbial integrity and survival on blueberries.     

The impact of dietary oil source and frozen storage on the physical,chemical and sensorial quality of fillets from market-size red hybrid tilapia, Oreochromis sp.

Red hybrid tilapia (Oreochromis sp.) were fed one of four diets containing either fish oil, crude palm oil, palm fatty acid distillates or refined palm olein as the only added oil. Post-harvest fillet quality was then evaluated at 1, 10 and 30 weeks of frozen storage. Dietary oil source did not significantly (p > 0.05) influence the liquid holding capacity and texture of fillets but both these parameters were increased by frozen storage. Fillets from fish fed palm oil-based diets exhibited significantly higher oxidative stability during frozen storage, compared to fish fed the fish oil diet. Dietary oil source and frozen storage had little impact on sensory attributes. Unlike fillet proximate composition, fillet fatty acid composition was significantly affected by both diet and frozen storage. Total n-3 polyunsaturated fatty acids decreased significantly in the fillet lipids of all fish after 30 weeks of frozen storage.     

Sensory,physical, chemical and microbiological changes in aquacultured meagre (Argyrosomus regius) fillets during ice storage

Commercial-sized meagre fillets were stored on ice at 4 °C for 18 days, in order to evaluate the loss of quality and freshness that occurs over this period of time. Physicochemical (pH, thiobarbituric acid (TBA), total volatile basic nitrogen (TVBN), trimethylamine (TMA), water activity, water-holding capacity, colour, texture and fatty acid profile), sensory and microbiological analyses were carried out at 0, 4, 7, 11, 14 and 18 days of storage. As part of the sensory analysis, attributes associated with fillet appearance, odour and texture were examined. Variations in pH, TBA, TVBN and TMA were observed throughout the storage period, although only TBA displayed a significant correlation with time (r = 0.96). L^∗ and b^∗ values increased, and the chroma and hue values decreased, reflecting the colour changes experienced by the fillets over time. With regards to the texture profile, hardness was significantly correlated with time (−0.68). All the sensory analysis attributes exhibited significant variations and correlations close to 1.00 with storage time, which is a reflection of the fillets’ loss of freshness. The correlation coefficients between aerobic mesophilic and psychrophilic bacteria, enterobacteria and coliform counts on the one hand and storage time on the other were also very high (0.99–1.00). A regression analysis using the acceptability limit set by the ICMSF standard (1986) for total aerobic mesophilic counts (7 log cfu/g) yielded a shelf-life for meagre fillets of 9 days. The TBA, sensory and microbiological analyses displayed very strong correlations with storage time, and they may be considered suitable indicators for evaluating meagre fillet spoilage during refrigerated storage.     

Effects of chitosan coating on quality and shelf life of silver carp during frozen storage

The effects of chitosan coating on quality and shelf life of silver carp during frozen storage were investigated. Fish samples were treated with aqueous solution of 2% chitosan, and then stored at −3 °C for 30 days. The control and the treated fish samples were analyzed periodically for microbiological (total viable count), chemical (pH, TBA, TVB-N, K-value), and sensory characteristics. The results indicated that the effect of chitosan coating on fish samples was to retain their good quality characteristics and extend the shelf life during frozen storage, which was supported by the results of microbiological, chemical, and sensory evaluation analyses.