The effect of preliminary processing and period of storage on the quality of frozen Boletus edulis (Bull: Fr.) mushrooms

This paper investigates the effect on the quality of frozen Boletus edulis (Bull: Fr.) mushrooms of blanching or soaking and blanching in aqueous solutions containing combinations of added substances safe for human consumption, or period of frozen storage. During 12 months of storage, sensory evaluations, instrumental colour measurements and chemical analyses of the frozen products were carried out every four months. Based on the results of the sensory evaluation, a maximum storage period of four months was set for the frozen product obtained from unblanched mushrooms. Frozen products having undergone preliminary processing retained good sensory quality for up to 12 months. Soaking, blanching and freezing resulted in the appearance of colours, such as yellow, honey and pink–violet. As a result of freezing, decreases in the contents of thiamine, riboflavin and vitamin C were noted. Blanching in water, as a method of pre-processing, was sufficient for maintaining acceptable sensory quality.     

Effects of blanching and storage conditions on soluble sugar contents in vegetable soybean

Vegetable soybean is becoming increasingly popular in the U.S. because of its rich source of isoflavones, folic acid, and other nutrients. The objective of this study was to investigate various blanching and storage conditions in order to identify the proper post-harvest management strategy in preserving sugar composition of vegetable soybean during storage. Fresh soybean pods of two vegetable soybean genotypes were stored at 4 °C for 30 days or 25 °C for 8-12 days in fresh air or nitrogen atmosphere. Shelled seeds and intact pods were blanched in boiling water or steamed at 100 °C for 10 min. All blanched soybean was stored at −20 °C and sampled monthly for 6 months for sugar analysis. Glucose, fructose and sucrose decreased gradually in fresh soybean when stored at 4 °C in air or nitrogen atmosphere for 28 days. Soybean stored at 25 °C in open air showed a rapid decrease of sucrose in the first 24 h, and then followed by a gradual increase; whereas oligosaccharides accumulated significantly during storage. Significant degradation in all sugars was found in soybean stored in nitrogen atmosphere at 25 °C. Soluble sugars decreased from leaching during the water blanching and cooling treatment of vegetable soybean seeds. Steam blanching and the presence of pod effectively retained soluble sugars in vegetable soybean during thermal treatment.     

Physical, textural and sensory characteristics of 7-day frozen part-baked French bread

Bread partially baked for 7 min at 250 °C, after cooling, was frozen until core temperature reached −18 °C and stored at this same temperature up to 7 days. Samples were removed daily from the freezer, thawed and baked at 250 °C for 6 min. Analyses were performed 1 h after final baking, and were also conducted on fresh French bread daily produced (control). Weight and specific volume of frozen part-baked bread presented significant difference (P<0.05) compared with fresh one. Sensory analysis was carried out by a trained panel using the Difference from Control test to evaluate the difference and the degree of difference between frozen part-baked French bread (FPBFB) and fresh bread regarding appearance, tactile by direct touch and mouthfeel. All scores obtained indicated that the panelists, during the studied period, considered FPBFB to be slightly different compared with fresh one. Consumer Acceptance test was applied to compare appearance (gloss, roughness and cut on bread surface), oral texture (crust crispness and crumb firmness) and overall flavor between frozen part-baked bread and a commercial brand. All sensory scores obtained from Consumer test indicated that the 4-day frozen part-baked presented a superior acceptance to the commercial brand.     

Effect of addition of cryoprotectants on the mechanical properties, colour and sensory attributes of fresh and frozen/thawed mashed potatoes

Cryoprotectants such as hydrocolloids (amidated low-methoxyl (ALM) and high methoxyl (HM) pectins), kappa- and iota-carrageenans (k-C and i-C), xanthan gum (XG)) and dairy proteins [whey protein (WP), sodium caseinate (SC)] were added to mashed potatoes to investigate ways of improving the effects of freezing and thawing. It was found that each hydrocolloid and protein, depending on concentration, affected the mechanical properties [instrumental textural profile analysis (ITPA), cone penetration (CP) test], the total colour difference (ΔE*) with respect to fresh control (FC) and the sensory attributes of fresh (F) and frozen/thawed (F/T) mashed potatoes in a different way. In the F/T samples, adding 5 and 8 g kg⁻¹ ALM, 3, 5 and 8 g kg⁻¹ k-C, 1.5, 3, 5 and 8 g kg⁻¹ i-C and 1.5, 5 and 15 g kg⁻¹ WP significantly increased ITPA consistency. Also, adding 2.5 and 5 g kg⁻¹ XG significantly increased ITPA consistency of the F/T product. In both F and F/T samples, k-C provided the highest ITPA consistency and also high CP average force evidencing a stronger synergistic effect in κ-C/denatured milk protein systems, although the excessive thickening and stickiness provided was judged undesirable by the panellists. Adding 8 g kg⁻¹ HM pectin had a disruptive effect on the mashed potatoes and decreased both ITPA consistency and CP average force. In all cases, freezing and thawing reinforced the gel structure of the products as compared to F and FC counterparts. The ΔE* values were higher in F samples containing ALM and HM pectins. Dairy proteins affected the taste and odour of the mashed potatoes and were judged unacceptable in the sensory analysis. Samples containing 0.5 and 1.5 g kg⁻¹ added XG were preferred organoleptically due to the creamy mouthfeel it produced. ITPA consistency correlated well with sensory texture attributes.     

The antioxidant activity and composition of fresh, frozen, jarred and canned vegetables

Regular consumption of dietary antioxidants may reduce the risk of several serious diseases. As vegetables are a major source of antioxidants it is desirable to assess their antioxidant activity and compare different processing and preparation methods. The total antioxidant activity was determined in water- and lipid-soluble extracts from fresh, stored and frozen vegetables. The contribution of individual compounds to total antioxidant activity was estimated. In stored vegetables at ambient or chill temperatures antioxidant activity declined. Blanching and freezing of peas and spinach reduced water-soluble antioxidant activity by 30 and 50%, respectively, thereafter levels remained constant on storage at −20 °C. Samples of frozen peas and spinach purchased from retail outlets had substantially higher antioxidant activity than canned or jarred samples. In a comparison of cooking methods, microwave and boiling for short periods had a negligible effect on total antioxidant activity, but substantial losses occurred after prolonged boiling in water.     

Phenolic content and antioxidant capacity versus consumer acceptance of soaked and vacuum impregnated frozen nectarines

Nectarines (Prunus persica L. cv. Maria Laura) were manually selected, cut in slices and divided into four groups: fresh, untreated frozen, soaked in osmotic solution and subsequently frozen, and vacuum impregnated (VI) and subsequently frozen. This investigation was focused on evaluation of consumer acceptance with respect to treated versus untreated frozen nectarine slices. In a preliminary acceptance test of untreated frozen nectarine slices, fruits were generally rejected on the basis of a darkened appearance and “oxidized” taste. These negative attributes were probably linked to the activity of polyphenol oxidase (PPO) and depletion of phenols due to cell rupture during freeze–thaw procedures. For these reasons, in order to evaluate the tendency of fruit to oxidation, several analyses were performed: the antioxidant capacity of phenolic fraction and the o-diphenol content were estimated by spectrophotometric assays, whereas the hydroxycinnamic acid (chlorogenic and neochlorogenic acids) composition was evaluated by high performance liquid chromatography (HPLC). Phenolic content and antioxidant capacity were found to correlate well with the acceptance level of frozen nectarine slices. In this regard a higher phenolic content associated with a higher acceptance level of nectarine samples.     

Effect of grape seed extract on oxidative, color and sensory stability of a pre-cooked, frozen, re-heated beef sausage model system

To compare grape seed extract (GSE) to common antioxidants in a pre-cooked, frozen, stored meat model system sausage was manufactured from lean beef (70%), pork fat (28%), and salt (2%). Antioxidants added for comparison with control included grapeseed extract (100, 300, and 500 ppm), ascorbic acid (AA, 100 ppm of fat) and propyl gallate (PG, 100 ppm of fat). Product was formed into rolls, frozen, sliced into patties, cooked on a flat griddle to 70 °C, overwrapped in PVC, then frozen at - 18 °C for 4 months. GSE- and PG-containing samples retained their fresh cooked beef odor and flavor longer (p < 0.05) than controls during storage. Rancid odor and flavor scores of GSE-containing samples were lower (p < 0.05) than those of controls after 4months of storage. The L* value of all samples increased (p<0.05) during storage. Thiobarbituric acid reactive substances (TBARS) of the control and AA-containing samples increased (p < 0.05); those of GSE-containing samples did not change significantly (p > 0.05) over the storage period.     

Sensory quality of short- and long-term frozen stored pork products. Influence of diets varying in polyunsaturated fatty acid (PUFA) content and iodine value

Predicting aspects of pork quality is becoming increasingly important from a nutritional as well as a technological point of view. Here, the influence of increasing PUFA and iodine values (IV) in feed and pigs on sensory qualities of short- and long-term frozen stored products was investigated. Entire male and female grower-finisher pigs were fed diets with iodine value products of 48 (LowIVP), 77 (MedIVP) or 99 (HighIVP) according to a restricted feeding scale. Ribs, chops and meat balls were short- (0-3 months) and long-term (6-9 months) frozen stored before sensory profiling. C18:2n−6 increased linearly in backfat with increased dietary inclusion. No negative effect on sensory quality was found in short-term stored products. After long-term storage the lean chops was the product most affected. Increasing the dietary IVP led to an increased rancid and total odour and flavour intensity, and to reduced meat and sour odour and flavour.     

Effect of frozen and dried leek on processing and quality characteristics of Greek traditional sausages

Blanching of leek at boiling temperature for 1min reduced (p<0.05) the nitrate content. Freezing of leek at -18°C and storage for 5 months, with or without vacuum, also reduced (p<0.05) the nitrate content, while drying at 85°C for 2h and storage for 5 months, with or without vacuum, had no effect (p>0.05) on nitrate content. Frozen leek as a whole plant was unsuitable for the production of traditional sausages. The most appropriate level of dried leek for sausage production was 20g/kg of meat mixture. The nitrate content of sausages with frozen and dried leek ranged on the 7th day from 24.5±14 to 36.3±13ppm and the nitrite content from 1.4±0.4 to 2.6±1ppm. Sausages with dried leek had better (p<0.05) colour, higher (p<0.05) pH and lower (p<0.05) TBA values. Sausages with frozen and dried leek had the same (p>0.05) sensory attributes as those produced with fresh leek. Vacuum packaging affected (p<0.05) the odour of fresh sausages with frozen and dried leek and the overall acceptability of fresh sausages with frozen leek. Sausages with frozen and dried leek stored under vacuum had higher scores for sensory attributes, which were not always significant.     

Effect of vacuum impregnation on the phenolic content of Granny Smith and Stark Delicious frozen apple <Emphasis Type="Italic">cvv</Emphasis>

ABTS•+ test, o-diphenols (spectrophotometric) and HPLC-DAD phenolic content in vacuum impregnated apple slices from Stark Delicious and Granny Smith cvv. were studied. Vacuum impregnation (VI) was carried out in a pilot plant using an aqueous solution containing 37.9% dextrose, 15.2% sucrose, 1.0% ascorbic acid, 0.25% calcium chloride and 0.25% sodium chloride. The impregnation time was 30 min and the vacuum pressure was 100 mbar; the temperature was 25 °C during all processing steps and the solution/fruit ratio was 11:1. At the end of VI, samples were left 5 min in syrup. They were then rinsed with water, drained in a vibrating screen and quickly frozen. A significant decrease (p < 0.05) of the o-diphenol content was seen (17.84 and 12.32% of the initial content in Stark and Granny varieties, respectively). The same trend was confirmed by HPLC-DAD where reductions in total phenols were 21.57 and 26.86% in Stark and Granny, respectively. Individual phenolic compounds showed different rates of depletion, although in some cases there was no reduction. The ABTS•+ test was strongly affected by the presence of ascorbic acid (AA), which was much higher in treated samples. Sensory evaluation showed higher values of hardness, crispness, juiciness and sourness in VI Granny Smith than VI Stark delicious, with a higher retention of texture parameters in the former. Finally, sweetness was slightly higher in VI Stark. An erratum to this article can be found at     

Effects of storage temperatures on the antioxidative activity and composition of yam

The effects of storage temperatures on the composition and antioxidative activities of one kind of Taiwanese yam tubers, Tainung No. 1 (TNG1) (Dioscorea alata), were investigated at room temperature (20 ± 8 °C), 17 ± 2 and 10 ± 1.5 °C. Measurements of the antioxidative activities included reducing power and α,α-diphenyl-β-pricryl-hydrazyl radical-scavenging activity. The crude lipid and fibre contents decreased with storage time at all three temperatures, but the reducing sugar contents increased during storage. Both the reducing power and DPPH radical-scavenging activity of TNG1 decreased after 3 and 11 weeks at room temperature and 17 °C, respectively. At 10 °C, significant decline in the reducing power was found after 14 weeks, while the DPPH radical-scavenging activity tended to increase after 7 weeks due to the microbes causing rottenness.     

Effect of processing treatments (frozen,frying) on contents of minerals in tissues of ‘frutti di mare’

The objective of this study was to determine the effect of thermal treatment (frying) of frozen seafood on the content of minerals and heavy metals. An analysis was conducted to compare concentration of sodium, magnesium, potassium, calcium, copper, iron, manganese, zinc, as well as lead, cadmium and mercury in the analysed tissues of invertebrates (shellfish – blue mussel, Japanese squid, white shrimp and octopus). Thermal processing (in this case, frying) applied to the frozen invertebrates was found to affect significantly the content of macro‐ and microelements as well as the content of heavy metals, except for potassium and manganese content in mussels and shrimps, respectively. Frozen and thermally treated (frying) mussels are characterised by significantly higher concentrations of the analysed minerals (except Na⁺, Ca⁺², Cu⁺²), as well as higher concentrations of cadmium and mercury. In turn, shrimps and squids are invertebrates with lower content of both macro‐ and microelements.     

Stability of arsenic compounds in seafood samples during processing and storage by freezing

In this study, the stability of arsenic compounds in fresh and frozen samples of raw, boiled and fried Atlantic cod (Gadhus morhua), Atlantic salmon (Salmo salar) and blue mussel (Mytilus edulis) were examined. Results show that the total arsenic concentrations of the fresh Atlantic cod and Atlantic salmon samples were not different from the frozen samples within the same seafood type. For blue mussel, the total arsenic concentration decreased significantly after storage. Inorganic arsenic was found only in blue mussels and, importantly, no significant increase of inorganic arsenic was observed after processing or after storage by freezing. The content of tetramethylarsonium ion was generally low in all samples types, but increased significantly in all fried samples of both fresh and frozen seafood. Upon storage by freezing, the arsenobetaine content was reduced significantly, but only in the samples of blue mussels.     

Effect of preliminary processing and method of preservation on the content of selected antioxidative compounds in kale (Brassica oleracea L. var. acephala) leaves

Vitamin C and polyphenol content as well as total antioxidative activity were investigated in fresh leaves of kale; in leaves after blanching or cooking; and in frozen and canned leaves. In 100 g fresh matter, kale leaves contained 384.9 mg polyphenols and 112.1 mg vitamin C, with a Trolox equivalent antioxidant capacity (TEAC) level of 1175 μM Trolox. Of the polyphenols identified in kale leaves, ferulic acid occurred in the highest amount (240.44 mg/100 g, constituting 62% of total polyphenols). Freezing was a better method of preserving kale leaves since the loss of nutritive constituents was lower than in the case of canning. Depending on preliminary processing and storage temperature, after one-year storage frozen leaves contained 82.9–171.3 mg polyphenols and 39.3–65.4 mg vitamin C, with TEAC at the level of 501–681 μM Trolox in 100 g. In canned leaves these values were: 91.3–94.1 mg polyphenols, 16.1–19.3 mg vitamin C and 268–293 μM Trolox.     

Changes in some nutritional,bioactive and morpho-physiological properties of common bean depending on cold storage and seed moisture contents

Seed moisture content is one of the most important storage parameters affecting the quality of stored common beans. This study was conducted to investigate the changes in some nutritional, bioactive and morpho-physiological properties of common bean stored at three different seed moisture contents (6.4, 11.7 and 17.3%), 4 °C and 65% RH for 12 months. Significant differences were determined in terms of examined properties depending on different seed moisture contents before and after storage. Protein, essential mineral contents, total phenolic content, bulk density, true density and electrical conductivity decreased consistently as seed moisture content increases both before and after storage. On the contrary, dimensional properties, shape index values, thousand grain weight and total flavonoid content increased linearly with increase of seed moisture content both before and after storage. As a result, protein, essential mineral contents (potassium, magnesium, calcium, iron, zinc, manganese), antioxidant activity, total phenolic and total flavonoid content of common bean significantly decreased at the end of 12 months storage compared with before storage, while the contents of heavy metals such as Co, Sn and Pb increased after storage. In addition to, highly significant and positive correlations were determined between L* and WI, b* and C*, Dg and Da, Dg and Sa, Sa and Sv, P and K, P and Ca, ash and pH, Zn and Cu, Se and As. The results of this study clearly indicated that low seed moisture content was the most suitable to maintain the quality of common beans for long-term storage.     

The sensory characteristics and rheological properties of soups containing oat and barley β-glucan before and after freezing

The aim was to study the effect of concentration and molecular weight of two oat and one barley β-glucan preparation on the perceived sensory quality of a ready-to-eat soup prototype before and after freezing. Oat1 was a bran-type preparation containing high molecular weight β-glucan; Oat2 and Barley were more processed and purified preparations with lower molecular weight. Nine soups containing 0.25-2.0 g β-glucan/100 g soup and one reference soup thickened with starch were profiled by a sensory panel and their viscosity and molecular weight of β-glucan was analysed.Freezing had no notable effects on the sensory quality of the soups. At the same concentration, soups made with the bran-type preparation were more viscous and had higher perceived thickness than soups made with processed, low molecular weight preparations. Barley soups had mainly higher flavour intensities than oat soups. Good correlations were obtained between sensory texture attributes and viscosity (r=0.70-0.84; P?0.001) and moderate correlations between flavour attributes and viscosity (r=−0.63-−0.80; P?0.001). Technologically, β-glucans are feasible thickening agent alternatives in soups. Preparations with lower molecular weight and viscosity are easier to add into a food product in higher quantities, but the role of high molecular weight β-glucan in physiological functionality has to be kept in mind.     

Effect of production process on the amino acid content of frozen and canned Pleurotus ostreatus mushrooms

The aim of the work was to determine the effects of the freezing and canning processes, followed by a 12-month storage, on the amino acid content of Pleurotus ostreatus mushrooms. The pre-treatment involved blanching, or soaking and blanching, in mushrooms in water or in solutions containing sodium metabisulphite, citric acid, l-ascorbic acid and/or low-methylated pectin. Freezing and canning resulted in significant decreases in the levels of alanine, glutamine, cysteine and tyrosine (6–39%), and, in the case of canned mushrooms arginine, glycine, serine, histidine, methionine and threonine (1–31%). Frozen products obtained from blanched mushrooms had significantly higher levels of 12 out of the 17 amino acids examined (4–28%) whereas, in canned mushrooms, only 5 amino acids showed higher levels (3–20%), than those obtained from soaked and blanched mushrooms. With the exception of samples blanched in water, frozen mushrooms had higher levels than canned mushrooms of all the investigated amino acids. Limiting amino acids were not found in mushrooms.     

Effects of 1 year long‐term freezing with different preservatives on milk cholesterol,progesterone and lactoferrin determination

This study was performed to determine the effects of long‐term freezing on milk composition and to evaluate the possible effects on analysis of four preservative substances (Azidiol, Kathon CG, NaOH and Thiomersal) on the determination of milk cholesterol, progesterone and lactoferrin concentration. Collected milk was separated in aliquots, stored at 20 °C in 10mL plastic vials and analysed after 1, 6 and 12 months. It could be shown that the preservatives are not equally appropriate for all analysing methods used in this experiment. Preservatives and storage conditions for milk samples have to be carefully selected during the study design depending on the parameters to be measured.     

Effects of freezing rates on starch retrogradation and textural properties of cooked rice during storage

The effects of freezing rates and storage temperatures on starch retrogradation and textural properties of cooked rice were evaluated. Cooked rice was frozen with different freezing rates and then stored at 4 °C for 14 days or −18 °C for up to 7 months. Starch retrogradation enthalpy (ΔH_r) of cooked rice was determined by a differential scanning calorimetry, and textural properties were determined by a texture analyser. The results showed that the ΔH_r and hardness values had a negative correlation with freezing rate, however, a positive correlation was found between adhesiveness and freezing rate. On the other hand, the advantages (lower hardness and higher adhesiveness, less starch retrogradaton) of cooked rice gained by rapid freezing, were lost quickly in the first 3 days of storage at 4 °C. However, rapid freezing combined with −18 °C frozen storage can effectively retard starch retrogradation and maintain the textural properties of cooked rice for at least 7 months. Therefore, high quality cooked rice can be produced by combined rapid freezing with frozen storage.     

Phenolic compounds and antioxidative properties of selected wines from the northeast of Thailand

The phenolic contents and antioxidative properties of selected wines, produced in the northeast of Thailand, were evaluated and compared, particularly those produced at Suranaree University of Technology (SUT) Farm as a case study. Nine wine varieties were used to evaluate their total phenolic content (TPC) by Folin–Ciocalteu method, free radical scavenging efficacy by DPPH method and reducing power by ferric reducing-antioxidant power (FRAP) method. The red wines had significantly higher (p < 0.05) amounts of total phenols, flavonoids and antioxidant activities (AA) compared to white wines. Capillary electrophoresis (CE) was used as a powerful and high performing tool for analysis of principal phenolic compounds in the wines. t-Resveratrol was found in Shiraz, Zinfandel and blended wine varieties. (+)-Catechin was found in all wine varieties, except in Chasselar Dore. (+)-Catechin was present in wines at a higher level than (−)-epicatechin. In red wine, gallic acid was the dominant phenolic acid found.