Studies on stability of blue grape anthocyanins

The stability of grape anthocyanins in grape squash and juice is influenced by the nature of packaging materials and preservatives. In grape squash losses were 65–70% in glass bottles, 64–67% in paper-aluminium foil-polyethylene (PFP) laminate pouches, 77–81% in polypropylene (PP) pouches and 68–73% in metallized polyester-polyethylene (MPP) laminate pouches during 60 days storage at 15–35°C. After 60 days, loss of anthocyanins was lower in samples preserved with sorbate than with benzoate, but not after 120 or 180 days storage. Sugar increased losses of anthocyanins, which were more stable in isolated model systems of sugar and benzoate than in grape squash and juice. Anthocyanins were most stable in anhydrous systems, and their rate of degradation progressively increased with water activity.     

The response of unripe Conference pears to modified atmosphere retail packaging

Unripe green Conference pears with initial firmness values of 46–55 N were sealed in modified atmosphere (MA) low density polyethylene (LDPE, 30μ) pillow packs and in perforated control packs on three dates during 1985–1986. Changes in pack atmosphere composition, skin chlorophyll content, flesh firmness and sensory quality were monitored during 14–20 days simulated shelf-life at 20°C. In MA packs, equilibrated atmospheres containing 5–9% CO₂ and < 5% O₂ developed within c. 3 days. Chlorophyll degradation was completely inhibited by MA and resumed when packs were perforated, but MA only partially retarded the rate of flesh softening. Variations in the rate of ripening changes in duplicate MA packs could not be explained simply by differences in pack atmospheres. Furthermore, pears retarded by MA packaging failed to develop the normal sweet, aromatic flavour and succulent, juicy texture of 'eating-ripe' fruit, even when the packs were perforated after 4 days.
The differences in the responses of pears and apples to MA packaging, and the limitations of using this technique for the commercial marketing of English pears are discussed.     

Chemical and colour changes related to the use of sorbates and ascorbic acid in pickled cucumbers and caperberries during long‐term storage

The evolution of two additives, potassium sorbate and ascorbic acid, during long‐term storage of pickled vegetables, as well as the impact of these additives on product colour, was investigated. For this investigation, cucumbers and caperberries packed in both glass bottles and plastic pouches were used. In general, the added sorbate level remained unchanged during long‐term storage irrespective of the packaging material. However, the ascorbic acid gradually disappeared at a significantly higher rate in plastic than in glass containers, and its level was higher in caperberries than in cucumbers. In the latter, the presence of sorbate caused a higher degradation rate of ascorbic acid compared to the absence of sorbate. Ascorbic acid had a protective effect against surface colour degradation in cucumbers packed in plastic pouches, whereas sorbate enhanced such degradation. However, in both pickled vegetables, ascorbic acid degradation had a significant impact on brine browning, particularly in plastic pouches.     

CHANGES IN QUALITY OF DEHYDRATED KIBBLED ONIONS DURING STORAGE

SUMMARY— Dehydrated kibbled onions. of the Egyptian variety, containing 4-5% moisture, were stored under different conditions and their keeping quality as influenced by storage variables determined. 3 packaging materials, namely cans, polyethylene and Saran pouches were used. Samples were stored at temperatures of 15, 25 and 35°C at 44% relative humidity for 39 wk. Temperature of storage was found to have the largest effect on product quality. The can package was found to be superior to the flexible pouches; however, Saran pouches could be used under certain conditions. Moisture content increased significantly in polyethylene pouches at all temperatures, but in Saran pouches only at 25° C Absorbance of onion extracts, as measure of browning, increased significantly with storage temperature and to a smaller extent due to packaging materials. Products in polyethylene deteriorated most, while the difference between Saran- and can-packed products was small. A similar trend in results was found in tristimulus color determinations. All products stored at 15° C and those in cans at 25°C were found to be of good organoleptic quality. The pyruvic acid development potential could not be used as a sensitive indicator for determination of product quality.     

Sorbic and benzoic acid in non-preservative-added food products in Turkey

Sorbic acid (SA) and benzoic acid (BA) were determined in yoghurt, tomato and pepper paste, fruit juices, chocolates, soups and chips in Turkey by using high-pressure liquid chromatography (HPLC). Levels were compared with Turkish Food Codex limits. SA was detected only in 2 of 21 yoghurt samples, contrary to BA, which was found in all yoghurt samples but one, ranging from 10.5 to 159.9?mg/kg. Both SA and BA were detected also in 3 and 6 of 23 paste samples in a range of 18.1–526.4 and 21.7–1933.5?mg/kg, respectively. Only 1 of 23 fruit juices contained BA. SA was not detected in any chips, fruit juice, soup, or chocolate sample. Although 16.51% of the samples was not compliant with the Turkish Food Codex limits, estimated daily intake of BA or SA was below the acceptable daily intake.     

Effects of palm oil quality and packaging on the storage stability of dry vegetable bouillon paste

Vegetable bouillon paste, prepared by dry-mixing of pre-produced dry ingredients with addition of semisolid palm oil, was stored at the slightly elevated temperature of 40 °C for up to 12 weeks for comparing modified atmosphere packaging (MAP; oxygen concentration initially below 0.5%) packaging with free availability of oxygen in order to identify the mechanisms leading to quality degradation. An increased browning and increased formation of volatile compounds related to Maillard reactions and oxidation of secondary lipid oxidation products were observed for the vegetable bouillon paste stored without limiting the oxygen availability. The use of palm oil (kept liquid by heating to 50 °C for one week) was further found to promote quality degradation as compared to fresh palm oil when the availability of oxygen was not limited by the packaging of the vegetable bouillon paste. For modified atmosphere packaging, the effect of the quality of the oil on storage stability of the product was less pronounced.     

Effect of temperature on chlorophyllase activity, chlorophyll degradation and carotenoids of Cavendish bananas during ripening

Changes in chlorophyllase activity, chlorophyll and carotenoid content of Giant Cavendish banana fruit peel during ripening were measured at tropical temperatures (30–34°C) and at 20°C to relate them to the greenish and yellow colours of the fruit ripened at these temperatures. At 30–34°C bananas remained green on ripening due to incomplete chlorophyll degradation while at 20°C complete degreening occurred and fruits turned yellow. Peel total carotenoid content remained constant during ripening and did not change with temperature. Free xanthophylls decreased while xanthophyll esters increased on ripening. Chlorophyllase activity increased during ripening and paralleled the respiratory climacteric, although activity was not consistently related to the differential degradation of chlorophyll at these temperatures. Exogenous application of ethylene and ethrel accelerated ripening, but had no effect on chlorophyllase levels, chlorophyll degradation and carotenoid content of bananas ripened at either 30–34°C or at 20°C.     

THE AROMA OF CANNED BEEF: PROCESSING AND FORMULATION ASPECTS

The influence of processing techniques and formulations on chemical and sensory aroma properties has been studied with the purpose of finding ways to improve the flavor of canned meat. HTST-sterilization, "aseptic" canning and sterilization in various packaging materials including flexible pouches have been investigated. It was found that "aseptic" canning and, especially, HTST-sterilization had a pronounced positive effect on aroma, in the latter case for samples packed in thin layers (flexible pouches). It was shown that addition of e.g., fumarate or maleate in small amounts (0.06–0.15%) before sterilization decreased the concentrations of hydrogen sulfide and mercaptans, and the additions of certain amino acids, e.g., arginine, decreased the concentrations of the aldehydes. Both types of ingredients resulted in an improved aroma. Storage changes have also been investigated. It was found that there was a tendency towards a more accelerated change in flexible pouches compared with rigid cans.     

Modified atmosphere packaging of common mushroom

Until recently, the films used for packaging fresh fruits and vegetables were not permeable enough to balance the high respiration rate of mushrooms. Consequently, modified atmosphere packaging (MAP) in sealed pouches or punnets was not appropriate for this commodity. Four microporous films in oriented polypropylene (OPP) and one film currently used to overwrap mushroom punnets (stretchable PVC) were tested. Mushroom punnets placed into pouches were stored at 4 and 10°C for 8 days. the influence of the modified atmosphere on the marketing quality of pre-packed mushrooms was assessed by measuring the external and internal colour, development stage, firmness and microbial growth. A mathematical model was used to predict the gas composition within the pouches at steady state as a function of the film properties and the characteristics of the plant tissues. the equation calculated from the simplified model shows a linear relationship between the reciprocal of O₂ concentration at steady state, (1/x) at 10 and 4°C and the reciprocal of the film permeability, (1/PmO₂).     

Role of sorbic acid in nonenzymic browning reactions in liquid and solid model food systems

Role of sorbic acid (SA) in browning development in model systems has been studied. In liquid model systems containing water-glycerol-glucose (WGG), water-glycerol-sucrose (WGS), 45% sucrose and 30% sucrose plus 15% glucose, SA degraded when stored at 37°C forming brown pigments. Addition of amino acids (glycine or lysine monohydrochloride) increased the rate of browning development while Cu²⁺ reduced SA degradation and browning development. In the absence of amino acids and SA, WGG and WGS systems did not brown appreciably.
In solid systems with SA adsorbed on microcrystalline cellulose, the maximum rate of browning occurred at 0.73 a_w , but maximum rate of SA loss was at 1.0 a_w . In all systems inclusion of amino acids reduced SA degradation but increased browning development. The rate of SA-induced browning was considerably higher than that caused by sugar-amino acid interactions.     

Stability of monosodium glutamate in green table olives and pickled cucumbers as a function of packing conditions and storage time

The effects of different packing conditions and storage times on the stability of monosodium glutamate (MSG) added to two different fermented vegetables (Spanish-type green table olives and pickled cucumbers) were studied. Factors such as packaging material (glass bottle versus plastic pouch), heat treatment (pasteurisation versus non-pasteurisation), and the presence or not of a preservative compound (potassium sorbate) were considered. The MSG content of pickled cucumbers was stable for up to 1 year of storage in all packing conditions studied. The MSG content also remained stable in pasteurised green table olives. On the contrary, MSG was extensively degraded (>75% degradation) after 54 weeks of storage in unpasteurised green olives with a higher degradation rate in glass bottles compared with plastic pouches. In the presence of potassium sorbate, MSG was also considerably degraded in olives packed in plastic pouches (>50% degradation), but hardly degraded in glass bottles. The results indicate that MSG degradation in olives is due to the action of both lactic acid bacteria and yeasts, with the formation of γ-aminobutyric acid as the major end-product.     

Modified atmosphere packaging to extend the shelf life of tomatoes

An experimental retail packaging system was used to compare the atmospheric com-position and relative humidity which developed within packs sealed with a range of plastic films with different permeability properties, and to study the effects of these conditions on the rate of ripening (as indicated by colour change) and sensory quality of tomatoes. In packs sealed with several polyvinylchloride (PVC) films or with K-resin (a butadiene-styrene copolymer), an atmosphere containing 3–9% CO₂+3−9% 0₂ developed within circa 3–4 days at 10 or 12.5°C. Ripening of part ripe fruit was retarded, but continued normally after the packs were perforated, with no obvious adverse effects on the smell, flavour or texture of the fruit. In packs sealed with less permeable films (e.g. cellulose acetate), the internal atmosphere equilibrated to 10–18% CO₂+ < 2% O₂, resulting in complete inhibition of ripening, a high incidence of rotting and tainting of the fruit. Very high (98% or above) relative humidity within sealed packs also encouraged fungal spoilage. The possible commercial applications and benefits of this type of modified atmosphere (MA) packaging are discussed.     

Storage Stability of Nonpackaged Irradiated Indian Mackerel (Rastrelliger kanagurfa) in Ice

The storage stability of eviscerated Indian mackerel (Rastrelliger kanagurta) irradiated at a dose of 1.5 kGy and held under melting ice was examined. Packaging in polyethylene pouches prior to irradiation gave a shelf-life of 25 days, while, nonpackaged, irradiated fish remained in acceptable condition up to 20 days. The nonpackaged irradiated fish has less irradiation odor and better appearance as compared with packaged irradiated fish during the course of ice storage. Uni-radiated and nonpackaged mackerel kept in ice were acceptable only for 14 days. The results suggest that pre-irradiation packaging was not essential for commercially adequate extension in shelf-life of the iced fish.     

EFFECT OF STORAGE CONDITIONS, PACKAGING MATERIAL AND METABISULPHITE TREATMENT ON THE COLOR OF DEHYDRATED GREEN BELL PEPPERS (CAPSICUM ANNUUM L.)

Green bell pepper dices were dipped in two metabisulphite solutions, 2400 and 3600 mg. kg‐¹, respectively, and dehydrated. The dehydrated peppers were sealed in laminated pouches of different oxygen and moisture transmission rates, and stored in the dark at 0, 10 and 20C for 12 weeks. Color was evaluated by objective color measurement and a sensory panel during storage. The different packaging materials did not significantly influence color retention, while the SO₂ treatments showed only limited differences in their effect, but storage temperatures significantly affected visual and objective color. The best correlation between visual color evaluation and the objective color measurements, was obtained for the a* (greenness) measurements. Panelists could discriminate between samples stored at 0 and 10C in contrast to a* measurements which did not differ significantly. Calculated hue angles exhibited the highest discriminatory ability of any of the objective color parameters.     

脱硫对熏硫‘黑叶’荔枝采后品质及果肉亚硫酸盐代谢的影响

本实验研究了脱硫对熏硫‘黑叶’荔枝果实采后品质、亚硫酸盐残留量和果肉中亚硫酸盐代谢的影响。测定对照（施保克）、熏硫和脱硫处理的果实4 ℃贮藏期间的色度值、褐变指数、腐烂率、亚硫酸盐残留量及果肉中亚硫酸盐氧化酶（sulfite oxidase,SO）、腺苷-5’-磷酰硫酸还原酶（adenosine 5’-phosphosulfatezoline reductase,APR）、亚硫酸盐还原酶（sulfite reductase,SiR）、丝氨酸酰基转移酶（serine acetyltransferase,SAT）和乙酰丝氨酸裂解酶（O-acetylserine (thiol) lyase,OAS-TL）活力和基因表达。结果表明：贮藏期间脱硫果实较熏硫果实提前转红;脱硫和熏硫荔枝的果皮褐变指数和腐烂率均较对照组显著降低;相比熏硫,脱硫使果皮水分质量分数降低和相对电导率升高的幅度更大,抑制呼吸的效果则相近;脱硫使果皮亚硫酸盐含量大幅降低,并使得果肉亚硫酸盐含量在贮藏16 d后降至接近对照组的水平;贮藏期间除APR外,熏硫和脱硫后果肉中其他4 种酶的活力均呈现上调,即贮藏过程中处理组SO、SAT活力分别较同时期对照组上调2.0、8.6～26.7 倍,而脱硫果肉SAT活力仅在贮藏0 d较对照组上调11.1 倍,之后迅速下降,贮藏32 d后与对照组无显著差异;熏硫和脱硫果肉中5 个基因的表达则均在贮藏中后期总体高于对照。上述结果表明,脱硫可加快熏硫荔枝果皮恢复红色,获得与熏硫相当的保鲜效果,大幅降低了熏硫荔枝的硫残留,保障其食用安全。脱硫和熏硫荔枝果肉中SO和SAT活力的上调表明,SO酶促氧化反应是荔枝果肉亚硫酸盐降解中占主导和最稳定的方式,SAT和SiR主导的还原途径则可能作为氧化途径的补充。     

不同贮藏条件对发芽蒸谷米品质的影响

为探究不同贮藏条件(包装材料、氧气含量和温度)对发芽蒸谷米的理化性质、生物活性物质、抗氧化活性、微生物学特性的影响,将发芽蒸谷米在真空和常压状态下分别包装在铝层压聚乙烯(aluminum-laminated-polyethylene,ALPE)和聚酰胺-聚乙烯(polyamide-polyethylene,PAPE)包...     

Degradation kinetics of ascorbic acid in encapsulated spray-dried honey powder packaged in aluminium laminated polyethylene and high-density polyethylene

The present study evaluated the stability of nutritionally rich encapsulated spray-dried honey powders in terms of hygroscopicity, glass transition temperature, total phenolic content, antioxidant activity and ascorbic acid using maltodextrin, gum arabic, and whey protein concentrate as carriers during a storage period of 180 days using high-density polyethylene and aluminium laminated polyethylene as packaging materials at 25°C (room temperature) and 35°C (accelerated temperature). The results revealed that temperature caused a negative influence on the glass transition temperature and stability of ascorbic acid. The kinetics of ascorbic acid degradation followed a first-order reaction with a reaction rate constant dependent on temperature and packaging material. Honey powder developed with whey protein concentrate as carrier agent and stored in aluminium laminated polyethylene pouches at 35°C possessed the highest antioxidant activity and ascorbic acid due to the presence of phenolic compounds in honey, aonla (Emblica officinalis. Gaertn), and basil (Ocimum sanctum) extract. The honey powders stored in aluminium laminated polyethylene pouches showed comparatively better antioxidant properties (total phenolic content, ascorbic acid, and antioxidant activity) and minimum hygroscopicity than the powders stored in high-density polyethylene at both the storage temperatures.     

Influence of frozen storage and packaging on oxidative stability and texture of bread produced by different processes

The influence of packaging barrier properties and frozen storage on phenolic and phytosterol content, oxidative stability and crumb texture of frozen dough, part-baked and fully baked frozen bread was investigated in comparison to conventionally produced bread. Samples were stored either in blue coloured high density polyethylene (PE-HD) or transparent polyester-polyethylene-ethylene-vinyl alcohol copolymer (PET-PE/EVAL/PE) pouches for 22 days at −18 °C. Packaging materials were different in oxygen permeability: 3.67 cm³m⁻²day⁻¹ bar⁻¹ for PET-PE/EVAL/PE and 2080 cm³m⁻²day⁻¹ bar⁻¹ for PE-HD material, which did not significantly change during storage. Total phenolic content and oxidative stability of bread samples decreased during storage depending on the process. Frozen dough bread had the lowest phenolics decrease and the highest oxidative stability. Total phenolic content and oxidative stability of frozen breads during 8 days were similar to conventional bread. The phenolics reduction was higher for samples stored in PET-PE/EVAL/PE laminate than in PE-HD packaging. Total sterol content did not significantly change during bread storage in investigated packaging and did not contribute to the oxidation. Bread firmness was affected only by the process and not by the storage time and packaging material.     

The effect of harvest date on the responses of Discovery apples to modified atmosphere retail packaging

In order to study effects of physiological maturity on responses of Discovery apples to modified atmosphere (MA) retail packaging, samples of fruit were picked at 3–4 day intervals over a 3-week period spanning the development of the climacteric rise in respiration and the normal marketing season for the variety. The apples were packed in MA (301∼.ethylene vinyl acetate) or perforated control packs and held under simulated marketing conditions at 10 or 20°C. The degree of modification of the pack atmospheres and the effects of MA packaging on fruit ripening changes were influenced by harvest date and related to the respiration rate of fruit when packed. MA packs were effective in retarding softening and skin colour changes in immediately pre-climacteric and early climacteric fruit. There was little risk of taint development, except during 14-day simulated marketing periods at 20°C. Little beneficial effect of MA packaging was found in apples harvested 4 days before the onset of the climacteric; relatively little deterioration occurred in such fruit in perforated control packs. Beneficial effects of MA packaging on ripening changes and quality attributes were reduced, and taint risk enhanced, when the technique was used for late picked fruit with much higher rates of respiration. Possible causes for the observed relationship between the different stages of physiological maturity of Discovery apples and their responses to MA packaging are discussed.     

Modeling of Active Modified Atmosphere Packaging of Endives Exposed to Several Postharvest Temperatures

Endives were sealed in low‐density polyethylene flexible pouches containing or not containing individual oxygen or carbon dioxide scavenger sachet and stored at 5 °C and 20 °C. A mathematical model has been applied to predict gas changes for these passive and active modified atmosphere packaging (MAP). The model took into account the respiration rate of endives, the transmission rate of gases through the film, the absorption kinetics of gas scavengers, and the temperature influence of all these parameters. Whatever the temperature, the model was successfully validated with root mean square error values still lower than 1 kPa and thus represented a real tool to improve the design of MAP for fresh fruits and vegetables. Oxygen scavengers reduced by half the transient period duration (50 h compared with 100 h without scavengers) and did not modify the gas equilibrium composition, suggesting a beneficial influence on keeping the quality of the product. The carbon dioxide scavengers’ influence was limited and needs further study with carbon dioxide‐sensitive products.