Oxidative stability of soybean oil in oleosomes as affected by pH and iron

The oxidative stability of oil in soybean oleosomes, isolated using the Enzyme-Assisted Aqueous Extraction Process (EAEP), was evaluated. The effects of ferric chloride, at two concentration levels (100 and 500 μM), on lipid oxidation, was examined under pH 2 and 7. The peroxide value (PV) and thiobarbituric acid-reactive substance (TBARS) value of oil, in oleosome suspensions stored at 60 °C, were measured over a 12 day period. The presence of ferric chloride significantly (P < 0.05) affected the oxidative stability of oil in the isolated oleosome, as measured by the PV and TBARS. Greater lipid oxidation occurred under an acidic pH. In the pH 7 samples, the positively charged transition metals were strongly attracted to the negatively charged droplets. However, the low ζ-potential and the high creaming rate at this pH, may have limited the oxidation. Freezing, freeze–drying or heating of oleosomes have an insignificant impact on the oxidative stability of oil in isolated soybean oleosomes. Manufacturers should be cautious when adding oleosomes as ingredients in food systems containing transition metal ions.     

Oxidative stability of UHT milk as influenced by fatty acid composition and packaging

Control milk and milk enriched with unsaturated fatty acids (3.3% fat) were heated using an indirect ultra-high temperature treatment, then stored at 20 °C in containers from different packaging materials: glass (no exposure to light), high density polyethylene (HDPE) packaging with light barrier (3-HDPE; no exposure to light) and monolayer HDPE (1-HDPE; 1000 lx). The decrease in antioxidant content and the formation of oxidation products were monitored over three months. For milk stored in 1-HDPE packaging, the available antioxidants were consumed at the same rate for both milk types, suggesting that oxidation is initiated in the serum phase. After depletion of these antioxidants, oxidation products were formed according to the fatty acid profile. When using a light barrier in the packaging, no oxidation products could be detected over three months.     

Comparative study of flavor, texture, and sensory in cream cheese and cholesterol-removed cream cheese

This study was performed to compare flavor, texture, and sensory profiles of cream cheese and cholesterolremoved cream cheese made from whole milk and cream. The cholesterol was removed by crosslinked β-cyclodextrin and the cheeses were stored at 7°C for 4 week. To quantify the flavor compounds, the cheeses (0, 1, 2, 3, and 4 week) were extracted by solid-phase microextraction, analyzed by GC-MS and quantified by GC-flame ionization detector (FID). Tentatively identified flavor compounds were 11 acids, 2 ketones, 1 amine, 1 alcohol, 2 lactone, and 1 alkene. In texture profile analysis such as hardness, cohesiveness, adhesiveness, and sensory analysis such as appearance, flavor, taste, and texture properties were not significantly different (p>0.05) between two cheeses. On the basis of our results, it is concluded that no adverse changes was shown in the cholesterol-removed cream cheese in flavor, texture, and sensory characteristics during 4-week storage.     

Changes in flavour volatiles of whole pasteurized milk as affected by packaging material and storage time

Changes in volatile profiles of whole pasteurized milk stored under fluorescent light at 4 °C, packaged in different containers were monitored for a period of 7 days in a study designed to differentiate between light-induced oxidative and purely autoxidative effects related to packaging material. Changes in volatiles were measured using solid-phase microextraction–gas chromatography/mass spectroscopy, while microbiological and sensory analyses were used to assess milk quality. Two distinct patterns of milk flavour deterioration were observed. In light-exposed samples, a light-induced oxidation mechanism prevailed while in light-protected samples, an autoxidation mechanism was apparent. Under both conditions, the concentration of selected odorous compounds increased with storage time. Microbiological data correlated poorly with both sensory and GC/MS data. Sensory data correlated well with selected volatile compounds pointing to dimethyl disulphide, pentanal, hexanal and heptanal as potential markers of fresh milk quality. Based on sensory analysis, the optimal shelf life of the whole pasteurized milk used in this study was approximately 5 days.     

Coagulation of buffaloe's milk and resultant Domiati cheese characteristics as affected by salting and replacement with sour cream butter milk

The action of rennet on buffaloe's milk replaced by 5, 10 or 15% of sour cream butter milk salted by either 6 or 10% before renneting or after the rennet action was studied as the non protein nitrogen (NPN) content. Buffaloe's milk without replacement of butter milk was taken as a control. Results revealed that addition of salt to milk before renneting inhibited the rennet action and consequently increased the coagulation time. The inhibition increased with the increase in the salting percent. In contrast, replacement of buffaloe's milk by sour cream butter milk enhanced the rennet action and shortened the coagulation time compared with the control. This effect was increased proportionally by the increase in sour cream butter milk. Enhanced protein breakdown, slightly higher accumulation of free fatty acids and good quality were observed in Domiati cheese treated with sour cream butter milk compared with the control. This effect was pronounced in case of 15% sour cream butter milk.     

Oxidative stability of virgin olive oil as affected by the bene unsaponifiable matters and tertiary-butylhydroquinone

During 16 h heating at 180 °C, the oxidative stability (OS) of virgin olive oil (VOO) as affected by the same concentrations (200 ppm) of tertiary-butylhydroquinone (TBHQ) and unsaponifiable matters of bene kernel (UKO) and hull (UHO) oils in terms of the inhibitory effect on the formation of conjugated diene hydroperoxides (OS(CDV)) and off-flavor carbonyl compounds (OS(CV)) was investigated. TBHQ was not able to considerably increase the OS(CDV) (7.51) of the VOO (7.2) and showed no synergistic effect with indigenous antioxidative compounds of the VOO (IOV) in this respect. However, it could significantly improve the OS(CV) (from 2.49 to 4.52), which was mainly due to its synergism with the IOV. The UKO increased considerably the OS(CDV) (to 11.8), and its OS(CV) (4.22) was nearly the same as that of TBHQ. The IOV still had marked contributions to the prevention of VOO oxidation but the majority of stabilizing effect was related to the UKO and its synergism with the IOV. The OS(CDV) in presence of the UHO was less than that of the VOO (5.96), although it significantly increased the OS(CV) (to 5.2), mainly due to the stabilizing effect of UHO and its synergism with the IOV.     

Proteolysis of Mahon cheese as affected by acoustic-assisted brining

 Mahon cheeses were brined in the presence of an ultrasonic field and ripened during 75 days at 12  °C and 85% RH. Secondary proteolysis (water-soluble N, non-protein N, and free amino acids) was measured and compared to that obtained for cheeses conventionally brined. There were no differences in water-soluble and non-protein N attributable to the brining treatment. However, cheeses acoustically brined exhibited higher concentrations of free amino acids. The release of total free amino acids was more pronounced during the first 15 days of ripening for both types of brining treatments. The changes in proteolysis (free amino acids) during cheese ripening caused by acoustic-assisted brining are indicative of a higher extent of proteolysis and may also improve cheese flavor. Received: 13 March 2000     

Sensory changes in extruded oat stored under different packaging,light and temperature conditions

The sensory quality of extruded oat, stored in light and darkness in packages with different oxygen transmission rates (including the use of an oxygen absorber), was evaluated after 3 months of storage at 38 °C and 10 months of storage at 23 °C. To reduce the costly and time consuming shelf life and packaging evaluation, the possibility of reducing the number of sensory attributes to be analyzed and to accelerate shelf life testing was studied.The intensity of oat odor, paint odor and crispiness were found to describe the main differences among the samples. By increasing the temperature from 23 to 38 °C for samples stored in darkness, packaging evaluation tests for extruded oat might be performed in approximately one third of the time. Changes in headspace oxygen concentration in the packages due to oxygen consumption were in agreement with the sensory changes in the oat.     

Yield and functionality of Cheddar cheese as influenced by homogenization of cream

Cheese milk was standardized (casein-to-fat ratio of 0.7) by blending 0.64% fat milk and 35% fat cream. Cream was homogenized at 0/0 MPa (CO), 3.5/3.5 MPa (H05), 6.9/3.5 MPa (H10) or 10.4/3.5 MPa (H15). Cream homogenization did not influence rennet-clotting time, but it increased rate of curd firming and increased curd firmness of cheese milk. Moisture and salt in moisture phase of cheese increased with homogenization. Moisture (37%) and salt (1.5%) adjusted yield increased 1.42, 3.44 and 3.85% in H05, H10 and H15, respectively, over CO. Homogenized treatment cheeses melted faster with age. Free oil in 1 week old cheeses was lowest in H10 and highest in H05 and increased in all treatments with age. Cheese hardness was not influenced by homogenization but decreased with age. Cheeses with homogenized cream had improved body and texture and flavor. Cream homogenized at 6.9/3.5 MPa was optimal for enhancing Cheddar cheese yield and functionality.     

Quality of fresh‐cut baby spinach grown under a floating trays system as affected by nitrogen fertilisation and innovative packaging treatments

BACKGROUND: Alternative techniques for cultivation of leafy vegetables such as a floating tray system and unconventional gas mixtures for post‐harvest active modified atmosphere packaging (MAP) could be of interest in the minimally processed vegetable industry. RESULTS: The combined effect of three pre‐harvest fertilisation doses (8, 12 or 16 mmol N L^?1) and three post‐harvest MAP conditions (passive, super‐atmospheric or N₂O‐enriched) on the main quality attributes of fresh‐cut baby spinach leaves throughout 10 days at 5 °C was studied. After 8 days of shelf life, spinach leaves fertilised with 8 and 16 mmol N L^?1 and stored under N₂O‐enriched MAP showed the lowest microbial growth, with good sensory quality. Such combined treatments also preserved the total antioxidant capacity sampled at harvest (8 g ascorbic acid equivalent antioxidant capacity kg^?1 f.w.). A decrease of 10–20% in total vitamin C content regardless of N fertilisation and packaging treatment was found during shelf life. Total phenolics content at harvest was 2 g gallic acid equivalents kg^?1 f.w., which was slightly decreased or preserved during shelf life while total chlorophylls were preserved for all treatments assayed around 550 mg kg^?1 f.w. CONCLUSION: No clear effect of fertilisation doses was observed during post‐harvest storage on overall quality of fresh‐cut baby spinach leaves, while N₂O‐enriched atmospheres seems to be a promising alternative to passive MAP for extending shelf life. Copyright © 2010 Society of Chemical Industry     

Quality of enoki mushrooms as affected by packaging conditions

Fresh enoki mushrooms (100 g) were packaged under various conditions and stored at 10 °C for 14 days. Package atmosphere, weight loss, stipe elongation, surface colour and sensory quality of the mushrooms were measured during storage. Different levels of initial vacuum application did not have a significant influence on the in‐package atmosphere after 2 days. The half‐vacuum package was best in terms of quality preservation of the fresh mushrooms. A polyolefin film with respective gas permeabilities of 166 and 731 ml m⁻² h⁻¹ atm⁻¹ to O₂ and CO₂ established an equilibrated atmosphere of 1.7–2.4% O₂ and 4.1–5.6% CO₂ inside the package at 10 °C. This polyolefin film was shown to contribute to preserving the freshness of the mushrooms. Temperature fluctuations between 5 and 15 °C did not induce a harmful atmosphere inside the polyolefin package, though high temperatures accelerated the quality loss. © 2000 Society of Chemical Industry     

Application of multiple factor analysis for the descriptive sensory evaluation and instrumental measurements of bryndza cheese as affected by vacuum packaging

Multiple factor analysis was used to examine naturally white, mature and spreadable bryndza cheese varieties. Sensory and physiochemical properties were evaluated during storage in vacuum and non-vacuum packed conditions at 4 ± 2°C. The results of statistical method showed similarity in varieties made from pasteurized ewe milk and mixed bryndza cheese before and after storage at both package conditions (p < 0.05). The statistical method used in the study was a suitable tool for assessing differences in food quality and provided an opportunity to visualize and categorize the results with regard to shelf life and packaging.     

加速氧化测试辣椒茎叶提取物对大豆油氧化稳定性的影响

食用油氧化稳定性是产品的一个重要指标,影响产品的安全性和货架期。采用加速氧化测定法,通过测定过氧化值(PV)、β-茴香胺值(p-AV)、共轭二烯烃(CD)和共轭三烯烃(CT)等指标研究辣椒茎叶提取物(PLSE)对大豆油氧化稳定性的影响。结果显示,在加速氧化测定条件下空白对照组大豆油4个指标逐渐增加,抗氧化剂BHT、BHA、TBHQ和提取物PLSE对大豆油氧化具有不同程度的抑制作用;10、100、200mg/kg剂量组PLSE对大豆油4个氧化指标的抑制作用均小于TBHQ(200 mg/kg),10、100、200 mg/kg剂量组PLSE对大豆油氧化指标PV和p-AV的抑制作用强于BHT(200 mg/kg)和BHA(200 mg/kg);而仅200 mg/kg剂量组PLSE对大豆油氧化指标CD和CT的抑制作用强于BHT和BHA。     

Oxidative stability and fatty acid composition of pig muscles as affected by rearing system, crossbreeding and metabolic type of muscle fibre

Muscle fibre type, fatty acid composition of phospholipids (PLs) and triacylglycerols (TGs) and susceptibility of muscle to lipid oxidation were studied in Biceps femoris (BF) and Tibialis cranialis (TC) muscles from Iberian and Iberian×Duroc pigs reared indoors and outdoors. Fatty acid composition of TGs was not affected by muscle fibre type and crossbreeding, but was strongly influenced by rearing system. In PLs crossbreeding slightly affected monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) content in BF muscle, whereas rearing system showed a great influence on fatty acid composition of PLs. Oxidative fibres showed a positive relationship with saturated fatty acid (SFA) and MUFA contents and a negative one with PUFA content of PLs. Susceptibility of muscle to lipid oxidation was strongly influenced by diet, animals reared indoors and fed on concentrates showing higher levels of 2-thiobarbituric acid reactive substances (TBARS). Iberian×Duroc pigs tended to show slightly higher values of lipid oxidation than pure Iberian pigs. With regards to muscle fibre type, BF had lower TBARS values than TC, although within muscle no relationship was found between muscle fibre type and lipid oxidation.     

Interaction between sodium chloride and texture in semi-hard Danish cheese as affected by brining time,dl-starter culture,chymosin type and cheese ripening

Reduced NaCl in semi-hard cheeses greatly affects textural and sensory properties. The interaction between cheese NaCl concentration and texture was affected by brining time (0–28 h), dl-starter cultures (C1, C2, and C3), chymosin type (bovine or camel), and ripening time (1–12 weeks). Cheese NaCl levels ranged from <0.15 to 1.90% (w/w). NaCl distribution changed during ripening; migration from cheese edge to core led to a more homogeneous NaCl distribution after 12 weeks. As ripening time increased, cheese firmness decreased. Cheeses with reduced NaCl were less firm and more compressible. Cheeses produced with C2 were significantly firmer than those produced with C1; cheeses produced with C3 had higher firmness and compressibility. In NaCl reduced cheese, use of camel chymosin as coagulant resulted in significantly higher firmness than that given using bovine chymosin. Overall, cheese NaCl content is reducible without significant textural impact using well-defined starter cultures and camel chymosin.     

Microbiological and visual quality of fresh-cut cabbage as affected by packaging treatments

Microbiological behavior of fresh-cut cabbage as affected by packaging treatments including high oxygen (MAP1: 70 kPa O₂+15 kPa CO₂/balanced N₂), low oxygen (MAP₂: 5 kPa O₂+15 kPa CO₂/balanced N₂), and moderate vacuum (MVP), in combination with gas permeable (LDPE) and barrier (Ny/PE) films, was investigated. Spoilage bacteria and pathogens were inoculated on shredded cabbage, and observed for viable cell counts during storage at 5°C. Overall population of the tested bacteria was noticeably reduced in MAP1 with Ny/PE, but was little influenced by MAP2. However, the inoculated bacteria in MVP with Ny/PE significantly increased or leveled off. In sensory evaluation, the barrier packages maintained better visual quality compared to the permeable. Results indicate that packages with high O₂ and CO₂ in the barrier film showed considerable microbial inhibition without deteriorating visual quality. Therefore, it can be applied as a promising tool to secure microbial safety of fresh-cut vegetables at refrigerated temperatures.     

Quality of fresh-cut tomato as affected by type of cut,packaging, temperature and storage time

Long-life Calibra tomatoes (Lycopersicum esculentum Mill.) were minimally fresh processed in slices or wedges and packaged in polypropylene (PP) trays. Passive and active (3 kPa O₂+0 kPa CO₂ and 3 kPa O₂+4 kPa CO₂) modified atmosphere packages (MAP) were used at 0 and 5 °C. After 14 days, the gas composition within passive MAP packages was 11–13 kPa O₂+5.5–6 kPa CO₂ and 8–9.5 kPa O₂+10.5–11.5 kPa CO₂ at 0 and 5 °C, respectively. The gas composition reached in active MAP at both temperatures for both types of cuts was around 7–10.5 kPa O₂ and 7–9 kPa CO₂. The highest C₂H₄ level (15 L L^–1) was found in passive MAP at 5 °C, while in active MAP at both temperatures about 6 L L^–1 C₂H₄ accumulated. After 7 days of storage at 0 °C, the tomato pieces showed better aroma, appearance and overall quality than those stored at 5 °C. No difference between MAP treatments was found, although both led to a better appearance and overall quality than controls in air. After 14 days at 0 °C, only MAP treatments kept a good flavour, overall quality and texture, with no differences between them. After 14 days at 5 °C in all treatments, the flavour fell below a fair condition and the slices showed a slight senescence. MAP significantly reduced total plate counts (TPC) of slices at 5 °C, although only active MAP reduced TPC in wedges after 14 days at 5 °C. A visibly better appearance and overall quality was found in slices than in wedges. The main factors influencing the quality of tomato pieces were the storage duration and temperature. To keep the quality of fresh-cut tomatoes, one should consider three factors for selection: a suitable low chilling sensitive tomato cultivar, an adherent placenta and optimal maturity stage at harvest.     

Fatty acid and sensory profiles of Caciocavallo cheese as affected by management system

The effect of season of the year associated with changes in feeding and management system (pasture-based vs. confinement) on milk and cheese fatty acid profile and on sensory properties of Caciocavallo cheese was evaluated on 3 mountain dairy farms. Each farm used a pasture-based feeding system from April to June and from September to October (PS), and a confinement system for the rest of the year (CS). As a consequence of grazing, PS milk showed higher percentages of C18:3, cis-9,trans-11 conjugated linoleic acid, and trans-11 C18:1, and a reduced percentage of C16:0. The fatty acid profile of cheese largely reflected that of the corresponding raw milk from which cheese was made. This led to a significant decrease of atherogenic index in cheeses produced from cows on pasture. Based on sensory analysis, cheese from animals kept on pasture was more yellow and had a lower intensity of butter and smoked odors than did CS cheese. In addition, grazing induced a lower intensity of bitter and a higher intensity of spicy flavors compared with cheese from CS animals. In regard to texture, pasture feeding resulted in higher intensity of friability and graininess. All cheeses performed well in consumer tests; the panel found all samples more than acceptable for overall liking, and for liking according to appearance, taste/flavor, and texture. Overall liking of Caciocavallo cheese, as assessed by slope analysis, was affected primarily by taste/flavor (raw slope k = 0.88) and texture (k = 0.97), whereas appearance had a lesser effect (k = 0.72). The acidic and sensory profiles of cheese were well discriminated, with healthier cheeses produced by grazing cows. Therefore, wider use of pasture should be promoted to accentuate this favorable feature. Based on the specific nutritional and sensory characteristics of mountain Caciocavallo cheese, particularly that obtained from grazing animals, efforts should be made to indicate the quality of this cheese to the consumer and improve product recognition.