Heated Ascorbic/Citric Acid Solution as Browning Inhibitor for Pre-Peeled Potatoes

Treatment of pre-peeled potatoes with heated ascorbic acid (AA)/citric acid (CA) solution to extend shelf-life was investigated. Potatoes were abrasion or high pressure steam peeled, heated for 5–20 min in 1% AA + 2% CA at 45–55°C cooled, and then dipped for 5 min in browning inhibitor (BI) solution containing 4% AA +1% CA +1% sodium acid pyrophosphate. Combined treatment inhibited potato discoloration for 14 days at 4°C compared to 3–6 days with BI treatment alone. Raw material and treatment conditions were selected to minimize graying and textural abnormalities encountered with some treatments. Treatment with heated AA/CA may be an alternative to use of sulfites to control browning in pre-peeled potatoes.     

Quality Changes in Fresh-cut Peach and Nectarine Slices as Affected by Cultivar, Storage Atmosphere and Chemical Treatments

The shelf-life of slices from 13 cultivars of peaches and 8 cultivars of nectarines, varied (between 2 and 12 days at 0°C). Controlled atmospheres of 0.25 kPa O₂ and/or 10 kPa or 20 kPa CO₂ extended the shelf-life at 10°C of ‘O'Henry’ or ‘Elegant Lady’ peach slices by 1–2 days beyond the air control. Low (0.25 kPa) O₂ acted synergistically with CO₂ levels of 10 and 20 kPa to induce fermentative metabolism as indicated by ethanol and acetaldehyde production. A 2% (w/v) ascorbic acid + 1% (w/v) calcium lactate postcutting dip resulted in limited reduction of cut surface browning and tissue softening in ‘Carnival’ peach slices.     

Storage Stability of Chicken as Affected by Map and Lactic Acid Treatment

The effects of MAP and/or pretreatment with lactic acid buffer were studied on the shelf-life of broiler carcasses, under conditions simulating market storage (4 and 7°C) in the State of Kuwait. Pretreatment with lactic acid buffer increased treated carcass shelf-life by 6–7 days when stored at 4°C and 5–6 days at 7°C. Likewise, pretreatment of MAP carcasses with the same buffer extended the shelf-life to >36 and 35 days, compared with 22 and 13 days for the untreated MAP carcasses. Pretreatment of poultry with lactic acid buffer, with or without MAP, provides a potential alternative for improving the storage quality of poultry.     

Control of Listeria monocytogenes in Vacuum-Packaged Pre-Peeled Potatoes

Growth of Listeria monocytogenes on the surface of fresh peeled potatoes, treated with sulfite or a commercial browning inhibitor (CBI), packaged under vacuum and stored at 4,15 and 28°C was determined. At 4°C, L. monocytogenes did not grow in all treated potatoes even after 21 days. At 15°C, L. monocytogenes grew to 7 log₁₀ CFU/g within 12 days in the potatoes treated with sulfite or CBI. At 28°C, L. monocytogenes population was greater than 3 log₁₀ CFU/g by 24 h in all samples regardless of treatment. Sulfites or a CBI appeared to provide a measure of safety in pre-peeled potatoes packaged under vacuum when kept at proper refrigeration temperatures.     

Effect of Heat Treatment and Selected Antimicrobials on the Shelf-life and Safety of Cooked, Vacuum-Packaged, Refrigerated Pork Chops

The shelf-life of refrigerated (2–4°C) pork chops inoculated with Clostridium sporogenes PA3679 and Staphylococcus aureus Z88 was examined in products sliced from loins cooked to 66°C (150°F), dipped in 5% polyphosphate blend, 2.5% potassium sorbate or 2% acetic acid solutions, vacuum-packaged and stored at 2–4°C. The effect of a second in-the-bag cooking step to 66°C (150°F) after vacuum packaging was also studied. Pork chops not reheated after packaging showed incipient spoilage after 15 days at 2–4°C, depending on surface treatment. The second cooking increased the shelf-life of refrigerated product to more than 60 days and reduced counts of inoculated cultures to undetectable levels. However, on exposure of the chops to simulated mishandling (24–25°C), clostridial growth was detected in all samples except those dipped in polyphosphate or acetic acid solutions.     

Postharvest Changes in Antioxidant Capacity,Enzymatic Activity,and Microbial Profile of Strawberry Fruits Treated with Enzymatic and Divalent Ions

Strawberry fruits are highly perishable and cannot be stored for more than 1–2 days at ambient condition. Therefore, it was thought desirable to enhance the shelf-life of harvested strawberry using pectin methyl esterase and divalent ions. The freshly harvested fruits of strawberry were treated with different concentrations of pectin methyl esterase (50–300 units) and divalent calcium ions (calcium chloride) for 5–30 min using response surface methodology—Box–Behnken design. The treated and untreated (control) fruits were packed in plastic punnets and stored at two different temperature conditions, viz., 7 °C with 80 % relative humidity (RH) and 25 °C with 60 % RH, for evaluating the shelf-life. Appropriate physico-chemical and microbiological parameters were determined at alternate days during their storage. Overall firmness and color values (L, a, b) decreased, while physiological weight loss (percent) increased during their storage. No food-borne pathogens, viz., Salmonella, Staphylococcus, and coliforms, were observed during storage. Total antioxidant capacity and ferric reducing antioxidant power decreased, while lipoxygenase and polyphenol oxidase activities increased during storage at 7 and 25 °C. The shelf-life of treated strawberry was found to be 10 days at 7 °C as against 6 days for control fruits under similar conditions. The treated strawberry had shelf-life of 2 days compared to 1 day for control maintained at 25 °C.     

BROWNING BEHAVIOR OF TAURINE AND PROLINE IN MODEL AND DRIED SQUID SYSTEMS

Model systems containing taurine or proline mixed with glucose at pH 6.4 were adjusted for water activity (Aw) to 0.99, 0.90, 0.84, 0.75 and 0.60 with celite. The browning rates measured during 96 h at temperatures between 5° and 45°C increased with increased temperature and reduced water activity. The model system containing taurine had a higher browning rate than that with proline at the same Aw and temperature. The browning rate with taurine at Aw = 0.60 increased 34 times at 45°C and 7 times at 35°C compared to that at 25°C. Decreases in Aw from 0.90 to 0.60 resulted in increased browning rate, 4.1 times at 45°C and 1.3 times at 35°C. The browning rate in model systems with proline followed the same pattern. Temperature had a more pronounced effect on browning rate than Aw. Browning was very slow in model systems at temperatures below 25°C. Evidence is provided that the Maillard reaction occurred in the mantle of squid (Illex argentinus) during air drying at 35°C. Dehydration resulted in loss of 50% of the taurine (from 22.3 to 11.6 mmoles/100g dry mass) and more than 60% of the proline (from 23.4 to 8.9 mmoles/100g dry mass). Total free amino acids remained unchanged when the moisture level was above 50% or Aw = 0.95. The browning intensity of the squid mantle increased 5 fold during drying. Taurine and proline were digested most at water activity above 0.95, while other amino acids were lost at a greater rate in the intermediate water activity range.     

Quality of Fungicide Treated and Individually Shrink-Wrapped Tomatoes

Fungicide-treated mature green and pink tomatoes were individually shrink-wrapped with plastic films and stored at 13°C and 18°C. Shrink-wrapped pink tomatoes lost less water than unwrapped tomatoes, but there were no significant shelf-life or quality differences. The shelf-life of mature green tomatoes at 18°C, however, was increased 10 days by shrink-wrapping. Color development of wrapped mature green tomatoes at 18°C was delayed. Wrapped fruit at both temperatures were firmer than the controls. Titratable acidities and soluble solids of wrapped fruit were lower than those of the unwrapped fruit at 13°C, while no significant changes were observed in citric acid or monosaccharide concentrations. The differences in titratable acidities and soluble solids in the wrapped and unwrapped fruit stored at 18°C were not significant.     

Short communication: Gelatinization and enzymatic hydrolysis characteristics relevant to digestion and analysis of glycogen granules isolated from ruminal protozoa

Glycogen is an α-glucan produced by rumen microbes from various feed carbohydrates. It may be digested ruminally or intestinally to provide nutrients. The physicochemical and enzymatic hydrolysis characteristics of microbial glycogen have not been described in detail, but do influence its conversion to absorbable nutrients in vivo, its nutritional comparability with plant starch sources, and its accurate analysis in vitro. The objectives of this study were to determine presence or absence of a gelatinization response and to describe enzymatic digestion characteristics of glycogen granules isolated from ruminal protozoa obtained from lactating dairy cows. Protozoal glycogen granules were determined to be 98.3% α-glucan. Granules displayed gelatinization, the breaking of hydrogen bonds between molecules or branches, at 65°C compared with purified wheat and corn starches, which initiated gelatinization at 50 and 65°C, respectively. Digestion of ungelatinized samples with amyloglucosidase for 2 h at 39°C showed approximately 3-fold greater hydrolysis to glucose for protozoal glycogen (25.2% of dry matter; DM) than for wheat (9.9% of DM) or corn (8.2% of DM) starches. Based on enzymatic digestion results, protozoal glycogen may be more readily digested than intact corn or wheat starches and should be gelatinized or the hydrogen bonds otherwise disrupted to allow more complete recovery in enzymatic analysis.     

静电场协同阻隔性包装对鲜切马铃薯贮藏过程中品质的影响

为了延长鲜切马铃薯的货架期,采用静电场处理与阻隔性材料真空包装相结合的方式贮藏鲜切马铃薯。以新鲜马铃薯切片为试材,以感官、白度值、褐变度、失重率、可溶性固形物含量及V_C含量为评价指标,选用高阻隔性材料尼龙/聚乙烯(polyamide/polyethylene,PA/PE)复合膜、聚乳酸(Poly(L-lactic acid),PLLA)薄膜进行真空包装及无任何包装的空白组为对照,分别置于电场和无电场两组环境贮藏,均设4℃、85%相对湿度。结果显示,通过单一变量对比分析发现,同种包装材料下,电场环境下的鲜切马铃薯褐变减缓,失重率减慢,在空白组中,施加电场贮藏下的马铃薯失重率可减少30%。而同一贮藏环境下,阻隔性相对较高的PA/PE膜所包装的样品较另外两组能更好地延缓褐变和减少失水。综合静电场和高阻隔包装的电场-PA/PE组保鲜效果最佳,贮藏期间反应色泽的指标白度值和褐变度始终优于其他组,失重率最小,贮藏第15 d时感官评分为6分,而其他组则均低于6分失去食用价值,并较好的保持了V_C含量及可溶性固形物的含量。     

Prevention of enzymatic browning of apple cylinders using different solutions

Inhibition of enzymatic browning and decay on cut surfaces of Golden Delicious apple using ascorbic acid, cysteine, sodium chloride, calcium chloride, citric acid and sodium ascorbate alone or in combinations was investigated at 4 and 10 °C for a storage period of 0, 7 and 14 days, in an attempt to find the most effective treatment. Apple segments immersed in ascorbic acid and citric acid alone showed visual traces of browning after 7 days storage at 4 °C. After 14 days storage, only ascorbic acid and ascorbic acid plus sodium chloride had moderate browning, while all other treatments were severely affected. However, at 10 °C, only ascorbic acid was effective in reducing the level of browning, although its effect was minimal after 14 days storage. Browning was more severe at 10 °C than 4 °C in all solutions. The browning measurement (a* value) became increasingly positive from 7‐ to 14‐day storage. Microbial decay was absent in all treatments within 7 days at 4 and 10 °C. However, three test solutions showed microbial decay after 14 days storage at 10 °C in addition to the control solution, which showed decay at both 4 and 10 °C storage temperatures.     

Changes in Quality Attributes During Storage of High-Pressure and Thermally Processed Pineapple Puree

The primary issue of the pineapple puree processing industry is its limited stability. The study compares the quality changes in high-pressure and thermally processed pineapple puree at different storage conditions and estimates the shelf-life. The untreated (S1) and treated samples (S2, S3, and S4 treated at 600 MPa/50 °C/13 min, 600 MPa/70 °C/20 min, and 0.1 MPa/95 °C/12 min, respectively) packed in ethylene vinyl alcohol (EVOH) and multi-layered (ML) polyethylene terephthalate (PET) pouches were stored up to 125 days at 5, 15, and 25 °C. The total color change (?E*) and browning index during storage increased according to zero-order kinetic model, whereas ascorbic acid (AA), total phenolics, and total antioxidant capacity followed the first-order decay. The overall sensory acceptability (OA) of S2 was higher than both S3 and S4 at 5 °C, and it dropped rapidly at 15 and 25 °C. The activity of polyphenol oxidase and pectin methylesterase in S3 and S4 was less than 10 % up to 120 days at 5 °C. The consistency (κ) and residual enzyme activity in S2 decreased with storage duration and temperatures. For estimating the shelf-life, the change in OA was crucial for S2 and S3, whereas retention of AA served as the critical parameter for S4. The sample S2 packed in ML pouch was found to be the best sample having the shelf-life (microbial count?<?6-Log cfu g^?1, ?E*?<?12, OA?>?5, and AA?>?200 mg kg^?1) of 120, 50, and 25 days at 5, 15, and 25 °C, respectively.     

Chemical Changes during Storage of an Alcoholic Orange Juice Beverage

Chemical stability of a pasteurized, noncarbonated, alcoholic orange juice beverage, (8% ethanol and 30% reconstituted Valencia frozen concentrated orange juice), was investigated. It was hot-filled into clear glass bottles under nitrogen and subjected to 14-wk storage at 4, 25, and 40°C. pH, °Brix, titratable acidity, and % alcohol remained constant throughout storage. Accumulation of furfural and darkening paralleled ascorbic acid degradation. The beverage exhibited 25 times more browning at 40°C and 9 times more at 25°C than at 4°C after 14-wk. d-Limonene decreased at all temperatures. Nitrogen headspace slightly improved stability at 40°C. Time and temperature were most significant in storage and long-tem shelf-life could only be achieved with refrigeration.     

Oxidative stability,shelf-life and stir-frying application of Torreya grandis seed oil

Torreya grandis seed oil, with a feature of Δ5-sciadonic acid (SA, 20:3 Δ5, 11, 14 ω-6), is an attractive woody oil as its potential health benefits in lowering blood and hepatic lipids and anti-inflammatory properties. In the present study, its oxidative stabilities at both room temperature and heating conditions were investigated by analysing oxidation stability index (OSI), shelf-life, changes of fatty acids, acid value and peroxide value during stir-frying tests. Also, its effects on the sensory qualities of stir-fried shredded potatoes were evaluated. The OSI of T. grandis seed oil was 2.97 h at 120 °C, which was 11.24% higher than that of the control soybean oil, contributing to a longer predicted shelf-life of 135–195 d for T. grandis seed oil than 127–180 d for soybean oil. T. grandis seed oil also exhibited superior thermal stability compared to soybean oil. The feature fatty acid, SA, only lost 2.48–5.73% (decreasing from 14.14 to 13.33–13.79%) under the optimised stir-frying conditions at 140–180 °C for 3–5 min. For the stir-frying shredded potatoes, T. grandis seed oil made it more pleasing in colour, odour and palatability. Due to its desirable oxidative stability at room temperature and stir-frying performance at high temperature, T. grandis seed oil is suitable for use as a domestic cooking oil.     

High temperature storage of infant formula milk powder for prediction of storage stability at ambient conditions

Hexanal formation and pentanal formation were found to be early signs of quality deterioration of both a high lipid infant formula milk powder and a high protein infant formula milk powder with similar lactose and water content; these aldehydes were sensitive predictors for shelf-life at ambient conditions using short term storage at temperatures up to 55 °C. Higher temperature loads such as 70 °C were found to induce rapid lactose crystallisation entailing a rising water activity, higher levels of free radicals, rapid browning and formation of Strecker aldehydes from protein degradation, of which all were found to be unsuitable for shelf-life prediction. Advanced glycation end products were not detected during storage at 25 °C for up to 18 weeks and the rate of oxygen consumption for the reconstituted milk drink was not affected by storage of the infant formulas at 25 °C; neither can be recommended for shelf-life prediction.     

Application of Browning Inhibitors to Cut Apple and Potato by Vacuum and Pressure Infiltration

Vacuum and pressure infiltration were investigated as means of applying ascorbatc- or erythorbate-based enzymatic browning inhibitors to apple and potato cut surfaces. Apple plugs infiltrated at 34 kPa pressure showed more uniform uptake of treatment solution and less extensive water-logging than plugs vacuum-infiltrated at 169–980 mB. Delicious and Winesap plugs and dice gained 3–7 days of storage life at 4°C when treated by pressure infiltration, compared to dipping. However, infiltrated dice required dewatering by centrifugation or partial dehydration to prevent water-logging. Pressure infiltration at 108 kPa extended the life of potato plugs by 2–4 days, compared to dipping, but was ineffective with potato dice.     

Antimicrobial and preservative activity of garlic on fresh ground camel meat. I. Effect of fresh ground garlic segments

A method to prolong the shelf-life of fresh camel meat, by the use of fresh garlic as an antimicrobial and preservative agent, has been established. Three storage temperatures (room temperature 20–22°C, incubator 12°C and refrigerator 2–3°C) were used in this investigation. Irrespective of storage temperature, treatments with 5, 10 and 15% (by wt.) of fresh garlic segments, ground with fresh lean camel meat, were found to increase the period of shelf-life, two-, three- and more than four-fold, respectively, compared with the corresponding control samples. After 4 days storage at room temperature, 12 days incubation and 28 days refrigeration, it was found that treatments with 15 and 25% garlic resulted i* complete inhibition of microbial growth with no sign of any organoleptic spoilage of the meat. The treated meat samples were fried for 15 min and found to be acceptable in taste and flavour by the local people in Saudi Arabia.     

Effect of Low-Dose (100 krad) Gamma Radiation on the Microflora of Vacuum-Packaged Ground Pork With and Without Added Sodium Phosphates

Survival and growth of naturally occurring or inoculated bacteria were studied in refrigerated (5°C), vacuum-packaged ground pork irradiated at 100 krad (1kGy). Numbers of naturally occurring mesophiles, psycbrotrophs and anaerobes or facultative anaerobes were reduced (P<0.01) by irradiation, whereas lactic acid bacteria were least affected. Partial bacterial recovery during subsequent storage at 5°C suggested sublethal bacterial injury due to irradiation. Irradiation prolonged shelf-life 2.5–3.5 days (30–44%) in uninoculated and 1.0–1.5 days in inoculated (10⁵ CFU/g) meat. Added sodium acid pyrophosphate (SAPP) (0.4%) contributed two additional days to inoculated, irradiated pork shelf-life but had no effect on the naturally occurring micrbflora. Lipid oxidation did not increase (P>0.05) due to irradiation and was unaffected by phosphates.     

Effect of washing with citric acid and antioxidants on the colour and microbiological quality of whole mushrooms (Agaricus bisporus L.)

The effect of washing with citric acid followed by anti‐browning treatment involving rinsing with sodium d ‐isoascorbate or sodium l ‐ascorbate on the colour, microbiological quality and bacterial blotch of whole mushrooms when stored at 5 °C for up to 13 days at 80% RH was evaluated. Washing with 1% citric acid reduced Pseudomonas counts avoiding bacterial blotch, but caused an important deterioration of colour. When washing with citric acid was followed by an anti‐browning treatment, mushrooms colour was improved, at the same time as bacterial blotch was reduced, although the decrease of Pseudomonas counts was smaller than in mushrooms washed only with citric acid. The most effective treatment was washing with 1% citric acid followed by anti‐browning treatment with 1.5% sodium l ‐ascorbate.     

EGG QUALITY AS AFFECTED BY STORAGE AND HANDLING METHODS

The quality and shelf-life of fresh eggs were studied under simulated climatic conditions as found in Kuwait. Three groups of eggs (unwashed, washed, and washed and oil treated) were used. The treated eggs were stored at 5°, 25°, 37° and 42°C. Internal and external quality and sensory evaluation of the eggs stored up to 75 days were determined. The quality of the unwashed and washed eggs stored at 37°C and 42°C deteriorated rapidly while the wash and oil treatment extended shelf-life but decreased in quality to C over a period of time. The percent weight loss in the oil treated eggs at all temperatures was about 0.6% while the washed and unwashed lost more depending upon the temperature and storage time. All parameters studied for interior quality showed that oil treated eggs were significantly better than untreated eggs even at 42°C. Sensory evaluation on boiled eggs indicated that changes in flavor and overall quality for untreated eggs stored at high temperatures were obvious while little change in texture was observed. It was concluded that under Kuwaiti conditions eggs should be oil treated directly after collection and stored at or below 25°C so that the quality and shelf-life can be extended significantly.