Effect of curing and pre-storage dip treatments on the control of storage mould of kola nuts

 The effect of curing kola nuts at 30  °C was evaluated at the Cocoa Research Institute of Nigeria, Ibadan, to determine the effect of curing time and delay between inoculation and initiation of curing on storage rot. For nuts inoculated 24 h prior to curing, 48–72 h curing at 30  °C gave optimal disease control. The incidence of rot was higher when the treatment was delayed for 48 h after inoculation. When artificially wounded and inoculated kola nuts were dipped in a solution of 1.0 g l^–1 of sodium bicarbonate for 2 mins, disease development was significantly reduced compared to the 0.5% sodium hypochorite treatment. Sodium metabisulphite also reduced disease development but the level of disease control achieved was not significantly different from that of the water-dipped controls. The in vivo results were consistent with the in vitro results.     

Effect of temperature on the cell wall composition of raisins during storage under a modified atmosphere

 Raisins obtained from seedless grapes ("Flame" variety) were kept under a modified atmosphere (MA) composed of CO₂ (60%) and N₂ (40%), and stored at 10  °C (10MA), 20  °C (20MA), 30  °C (30MA) and 40  °C (40MA). An additional sample was stored under air at 20  °C (20A). Colour, and changes in cell wall components were monitored during storage. At the end of the storage period, the 40MA and 20A samples showed a significant decrease (∼18–19%) in the yield of cell wall material (CWM), whereas less than 6% of CWM had been degraded in the 10MA sample. The decrease in CWM was mainly due to pectic polysaccharide degradation, although for 20A and 40MA samples, hemicelluloses were also affected. Throughout storage, 10MA, 20MA and 30MA samples exhibited similar CWM solubility; however, that of the 40MA sample underwent a significant decrease, from 10% to 4.5%, probably due to the formation of new pectic chains of higher molecular weight. In contrast, the CWM solubility of sample 20A increased from 10% to 15%, suggesting that MA may have promoted the inhibition of pectic-polysaccharide-degrading enzymes. In general, the combined use of relatively low temperatures and a MA helped to preserve both the colour of raisins and maintain the levels of their CWMs at values similar to initial concentrations. Received: 5 October 1998     

Effect of gluten addition and storage time on white pan bread quality: instrumental evaluation

 Continuing an investigation into the different factors affecting the quality of white pan bread and the changes taking place during storage, on the basis of instrumental determinations of firmness using compression and bending tests, this second instalment addresses the influence of adding gluten to the dough. Three types of bread were prepared using three different water contents and three proportions of added gluten each. Firmness was evaluated at 24, 48 and 72 h. Addition of gluten significantly increased flexibility and significantly decreased firmness in the bread at the higher water content levels. It also improved the keeping properties of the bread by slowing the increase in firmness with time; this effect was also higher at the higher water content levels. Received: 4 May 1998     

Effect of storage environment on carrot root rots and biochemical changes during storage

 The optimum temperature and relative humidity for the development of carrot root rot during storage were found to be 20°C and 60%, respectively, and rot development increased as these environmental factors increased in magnitude. Temperature and relative humidity both enhance the biodeterioration of the carrot root through an increase in the diameter the rotted area of infected roots. The rot during storage was found to be caused by Rhizopus oryzae, Trichoderma harzianum, Botryodiplodia theobromae, Aspergillus niger and Aspergillus flavus. The fungi enter through wounds and natural openings. The amounts of total soluble sugar in rotted carrot root were substantially decreased 2 – 4 days after infection and paper chromatography showed the presence of glucose, maltose, sucrose, lactose and galactose in healthy carrot roots, while only lactose and galactose were present in infected roots. The ascorbic acid, total nitrogen, crude protein, crude fibre, fat and mineral contens in infected carrot roots reduced as the storage period was prolonged. Received: 16 October 1996     

Variations in the phenolic composition of fruit juices with different treatments

 In this work we have determined the variations in the composition of phenolic compounds of natural peach and apple juice with different thermal and enzymatic treatments. The following phenolic compounds were identified and quantified in samples of treated and untreated fruit juices: cinnamic acids (caffeic, p-coumaric and ferulic acids), cinnamic derivatives (chlorogenic and p-coumarylquinic acids and feruloylglucose), flavonols (quercetin glycosides), dihydrochalcones (phloretin glycosides), flavan-3-ols [(+)-catechin and (−)-epicatechin], and procyanidins (dimer B₂, trimer C₁ and tetramer T₄). Furfural derivatives, compounds widely used as indicators of prior thermal treatment, were also studied using these samples. The results indicate that the different processes tested gave rise to a series of changes in composition that may make it possible to identify the type of treatment employed on the basis of the composition of phenolic compounds in the fruit juices. Received: 18 March 1996     

Effect of selected mould strains on lipolysis in dry fermented sausages

 Several batches of fermented sausages were prepared and inoculated with five strains of moulds belonging to the genera Penicillium and Mucor, selected for their enzymatic activity, and a strain of Penicillium nalgiovense obtained as a commercial starter culture. Control batches were manufactured similary, but without inoculation. Sausages were produced with either artificial or natural casings, and very similar results were obtained with both. The evolution of the different lipidic fractions was monitored, paying special attention to the free fatty acid (FFA) fraction. Two strains presented a high lipolytic activity as indicated by the rise in FFA in comparison to control batches. In conclusion, not all the mould strains contributed to the lipolytic process occurring during sausage ripening and, therefore, not all of these had a positive effect on the final quality of the product. If moulds are to be used for this purpose it is, therefore, necessary to carefully select suitable moulds beforehand. Received: 25 September 1998 / Revised version: 4 February 1999     

Influence of extraction method and storage conditions on the volatile oil of wormwood (Artemisia absinthium L.)

 In order to determine the best extraction procedure for volatile oil composition studies in wormwood (Artemisia absinthium L.), several extraction techniques have been investigated. In pentane extracts obtained using microwave or ultrasound sources of radiation, no thermic degradations occurred, but high amounts of heavy oils and waxes resulted, causing trouble in the gas chromatographic analysis. Headspace extraction provided the most volatile constituents, but high molecular weight compounds were not extracted. Simultaneous distillation-extraction resulted in the most adequate extraction procedure for volatile oil composition studies since the required compounds were extracted with minimum degradations when the distillation time was no longer than 30 min. Freezing and drying processes did not greatly affect the percentage composition of wormwood volatile oil. Received: 29 June 1998 / Revised version: 8 October 1998     

Effect of frozen storage on lipids and lipolytic activities in the longissimus dorsi muscle of the pig

 Samples of longissimus dorsi muscle from pigs were vacuum-packed and stored at –18  °C for a 6-month period. The quantity of total lipids, non-polar lipids, phospholipids and cholesterol remained unchanged during storage. However, there was a decrease (1.4%) in the polyunsaturated fatty acid percentage of the phospholipid fraction after 6 months of frozen storage, mainly due to the decrease in linoleic fatty acid. Nevertheless, there was no change in fatty acid composition of the non-polar lipid fraction. Phosphatidylethanolamine was the phospholipid most affected during the frozen storage, with a significant decrease from an intial percentage of 26.6% to 23.0% after 6 months of storage. Important activities of muscle lipolytic enzymes were still recovered after the storage, which explains the continuous release of free fatty acids reported during the process, with a net increase of 50.6 mg/100 g dry matter. The highest release of free fatty acids was reported during the 1st month of frozen storage. At the 6th month of frozen storage the compositions of both the free fatty acid and phospholipid fractions were similar. With respect to oxidation, the thiobarbituric acid test number showed a slight increase during the process while the peroxide value remained unchanged. Received: 16 March 1998 / Revised version: 17 June 1998     

Quality control charts for storage of raisins and dried figs

 Shewhart control charts are constructed by using the Hunter Lab color scale parameters to assure maintenance of the color of raisins and dried figs during storage in modified atmosphere packages, vacuum packages, or nylon bags. These control charts may be used to maintain the quality within acceptable limits and make it possible to readjust storage conditions if the acceptable limits should be violated. Received: 11 March 1996     

减压处理对水蜜桃保鲜效果的影响

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Efficacy of preharvest and postharvest Candida sake biocontrol treatments to prevent blue mould on apples during cold storage

This study compared the biocontrol efficiency of preharvest and postharvest applied yeast cells of Candida sake to apples (cv. Golden Delicious) wounded before and after harvest and inoculated with Penicillium expansum prior to cold storage conditions in two seasons, 1994/95 and 1995/96. The establishment of populations of C. sake during this period also was determined. In both years, postharvest treatment with the antagonist resulted in significant (P<0.05) and effective control of Penicillium rot whether pre- or postharvest wounds were made. Maximum disease control achieved, in terms of incidence and severity, was greater than 80% reduction in lesion diameter and 50% reduction in the incidence of lesions. However, preharvest application of the antagonistic yeast at a concentration of 3·10⁶ CFU/ml was less effective against Penicillium rot than postharvest treatment. No advantages in biocontrol were observed when apples were treated with the yeast antagonist both pre- and postharvest. Candida sake population levels during cold storage of apples receiving only preharvest application of the antagonist decreased prior and more rapidly than levels in apples receiving a postharvest application. High populations of C. sake were present in postharvest-treated apples, even after 90 days in cold storage.     

Effect of water content and storage time on white pan bread quality: instrumental evaluation

 The firmness of white pan bread was measured using compression and bending tests to determine the influence of the water content of the dough on bread quality and on the changes taking place with storage time. Three sample breads were prepared using different flours and three different water contents, and firmness was tested at 24, 48 and 72 h. For gluten-enriched flours, higher water contents tended to bring about a decrease in compression force and bending values, improving shelf-life by reducing the increase in firmness over time. Received: 24 March 1997     

Effect of water content and storage time on white pan bread quality: instrumental evaluation

 The firmness of white pan bread was measured using compression and bending tests to determine the influence of the water content of the dough on bread quality and on the changes taking place with storage time. Three sample breads were prepared using different flours and three different water contents, and firmness was tested at 24, 48 and 72 h. For gluten-enriched flours, higher water contents tended to bring about a decrease in compression force and bending values, improving shelf-life by reducing the increase in firmness over time. Received: 24 March 1997     

Effect of turgor pressure on the cutting energy of stored potato tissue

 Potato tissue samples with varying cell turgor pressures were prepared by soaking them in mannitol solutions (0 M to 0.9 M). Increased concentration of mannitol in the soaking solutions decreased the cell turgor pressure in potato tissues, providing samples with varying degrees of turgidity or plasmolysis. The firmness of potato tissues with different turgor pressures was periodically examined over a 12-week period using cutting tests. The occurrence of incipient plasmolysis was evident after soaking in 0.7 M mannitol solution as supported either by microscopic observations or cutting energy values. The cell turgor pressure of unsoaked tissue decreased during the first 2 weeks, increased between 2 and 4 weeks and finally decreased again up to 12 weeks. The cutting energy of unsoaked tissue showed an inverse trend between 2 and 8 weeks, demonstrating the ability of this mechanical parameter to detect the increase of cell wall stiffness as a function of storage time. Received: 8 June 1999     

Effect of dietary levels of fat, α-tocopherol and astaxanthin on colour and lipid oxidation during storage of frozen rainbow trout (Oncorhynchus mykiss) and during chill storage of smoked trout

 Female rainbow trout (Oncorhynchus mykiss) with an initial weight of 0.8–0.9 kg were raised in two experiments including a total of 2550 fish divided into 17 groups. The fish were raised for 6 months on 13 different feeds (four fish groups were replicates) varying in dietary levels of fat (27% or 32%), astaxanthin (40, 70 or 100 mg astaxanthin/kg feed) and vitamin E (α-tocopherol; 100, 300 or 600 mg all-rac-α-tocopheryl acetate/kg feed). The levels of fat, astaxanthin and α-tocopherol in the fillets all increased with increasing dietary levels of each feed component. Furthermore, astaxanthin deposition was found to be significantly improved by increasing the dietary fat level from 27% to 32%, but was not affected by dietary levels of α-tocopherol. The highest deposition of α-tocopherol was found in fish fed the lowest level of astaxanthin (40 mg/kg), whereas α-tocopherol deposition was unaffected by the dietary fat level. Frozen storage (–28  °C) of gutted, cleaned and glazed raw fish for 18 months significantly reduced astaxanthin and α-tocopherol levels, while lipid oxidation, measured as thiobarbituric acid reactive substances (TBARS) was limited. In the first experiment, the highest TBARS levels were found during frozen storage in fish fed the lowest level of astaxanthin (40 mg/kg versus 70 mg/kg or 100 mg/kg); unaffected by dietary levels of α-tocopherol (100 mg/kg versus 600 mg/kg), whereas the dietary astaxanthin level (70 mg/kg versus 100 mg/kg) did not influence lipid oxidation in frozen fish in the second experiment. After brine injection, fillets of fish were smoked and a vacuum-packed (95%), sliced product in a transparent laminate was produced. The quality (pigmentation and lipid oxidation) during 3 weeks of illuminated, chill storage (3  °C) was compared for smoked products produced from fresh fish and from fish stored at –28  °C for 12 months and 18 months. Smoked fillets from fish fed 32% fat were found to be less red than those from fish fed 27% fat, and the astaxanthin content and surface redness of the smoked product decreased during chill storage. Lipid oxidation was pronounced in smoked trout, but a high level of α-tocopherol in the fillet significantly reduced lipid oxidation during chill storage of the smoked product. Lipid oxidation in smoked fillets from fish fed 32% fat was more pronounced than in fish fed 27% fat, but increasing the dietary α-tocopherol level from 300 mg/kg feed to 600 mg/kg feed effectively counteracted the negative effect of the high-fat diet on lipid oxidation in the smoked product. Astaxanthin did not affect lipid oxidation in the chill-stored smoked product, in contrast to the frozen, raw fish. Astaxanthin seems to protect against the very early stages of lipid oxidation, while α-tocopherol is more important as an antioxidant at more advanced stages of lipid oxidation. Received: 8 January 1998 / Revised version: 23 March 1998     

Effect of edible coating and gamma irradiation on inhibition of mould growth and quality retention of strawberry during refrigerated storage

The aim of this study was to investigate the effect of edible coating and gamma irradiation treatment on mould growth and storage quality of strawberry. Strawberry fruit after harvest were treated with 0.5–1.0% (w/v) carboxymethyl cellulose (CMC) coating followed by irradiation at 2.0 kGy and subsequent storage under refrigerated conditions for 21 days. The investigations revealed that CMC coating alone at levels 0.5% and 0.75% w/v was not effective in delaying the decay and inhibiting the appearance of mould growth in strawberry fruit. Treatment of irradiation in combination with 1.0% w/v CMC coating was found significantly (P ≤ 0.05) effective compared with other treatments in maintaining the quality and delaying the decay and appearance of the mould growth in strawberry up to 18 days of refrigerated storage. Combinatory treatment of irradiation and coating can help to a greater extent in facilitating the marketing of the strawberry fruit to distant markets other than the local market, thereby benefiting growers and consumers.     

Effect of steaming on the rheological characteristics of wheat flour dough

 The effect of steaming on the various rheological characteristics of wheat flour dough was studied. Steaming of flours at atmospheric pressure for 15 min completely denatured the gluten and reduced the water absorption capacity from 58.4% to 45.0%. Even steaming for just 5 min increased the resistance to extension considerably from 500 BU (Brabender Units) to 1000 BU and the ratio figure (resistance to extension/extensibility) from 4.2 to 27.4, indicating stiffening of the dough. The dough made from steamed flour had a higher hardness value of 91.1 N than the dough made from raw wheat flour which had a value of 51.1 N. The pasting characteristics of flour steamed for 15 min measured in a Rapid Visco Analyser showed increased peak viscosity from 218 rapid visco units (RVU) to 257 RVU as well as increased cold paste viscosity from 175 RVU to 200 RVU and increased hot paste viscosity from 94 RVU to 108 RVU for flour steamed for 15 min. Received: 4 August 1998 / Revised version: 23 October 1998     

Effect of frozen storage on the quality of whole fish and fillets of horse mackerel (Trachurus trachurus) and mediterranean hake (Merluccius mediterraneus)

 Whole fish and fillets of horse mackerel (Trachurus trachurus) and mediterranean hake (Merluccius mediterraneus) were assessed for quality (physical, chemical and sensory attributes) changes throughout 12 months of frozen storage at −18 °C. The pH, expressible water (EXW), quantities of trimethylamine (TMA), dimethylamine (DMA), formaldehyde (FA), the total volatile base nitrogen (TVB-N) the thiobarbituric acid number (TBA), peroxide value (PV) and amount of free fatty acids (FFA) increased, while sensory attributes (odour, taste, texture) decreased during the frozen storage period. A comparison of quality scores between whole fish and fillets of horse mackerel and mediterranean hake showed that there were no significant differences (P>0.05) in attribute scores. There were, however, significant differences (P<0.05) in pH, EXW, TMA, DMA, FA, TVB-N, TBA, FFA and PV. Received: 19 April 1996/Revised version: 7 September 1996     

Long-term feeding effects of thermally oxidised oils on the absorption, storage and excretion of fat in rats

 The long term effects of feeding heated and fried vegetable oils namely peanut, sesame and coconut oils, at levels of 5% and 20% for 20 weeks on the absorption, storage and excretion of fat were studied in laboratory rats. Although no significant difference in the absorption rate of heated fats was observed, a marginal increase in the levels of fecal fat excretion was noted in heated/fried oil-fed rats. Deposition of fat in the perirenal adipose tissue indicated higher levels of palmitic and oleic acid in heated/fried oil-fed rats. Received: 14 June 1999 / Revised version: 2 August 1999