Staling of fresh and frozen gluten-free bread

The difficulty in finding gluten-free bread and its high price make it necessary to prolong its shelf life to facilitate its availability. Freezing is an interesting alternative. The storage of bread at over zero temperatures, 20 °C and 4 °C, showed faster staling at refrigerator temperatures. A good relationship between crumb firmness and the extent of starch recrystallization was obtained, although the effect of water loss was also detected. The study of freezing and frozen storage at −14 °C and −28 °C for 7 days showed a substantial effect of the storage temperature on gluten-free bread quality and shelf life. Breads stored at −28 °C retained a quality similar to that of fresh breads while a marked deterioration of the breads stored at −14 °C was observed. This effect, the strongest on bread texture, was a result of starch recrystallization. The glass transition, T_g’ and onset of ice melting, T_m’ of the maximally freeze-concentrated bread crumb were −37.1 ± 0.6 °C and −19.3 ± 0.2 °C respectively. The higher amount of unfrozen water at −14 °C could explain the acceleration of reactions responsible for bread staling during frozen storage. The use of storage temperatures below T_m’ is recommended to retain high quality of the gluten-free bread during frozen storage.     

An evaluation of the effect of Bacillus cells and Bacillus spores in association with cowpea granules as starter cultures for the fermentation of African oil bean (Pentaclethra macrophylla Bentham) to `ugba'

Studies on the improvement of the traditional production of `ugba',a protein-rich fermented African oil bean seed product, were undertaken,by developing starter cultures of Bacillus subtilis cells andspores in association with cowpea granules. The viability of the cellsin association remained stable at 94.5% for 6 months at 30 <sup>°</sup>C and for up to 10 months at 4 <sup>°</sup>C while the viability of the sporesin association remained stable at ca. 96% for up to 10 months at both4 and 30 <sup>°</sup>C. The starter cultures resulted in high increases inprotease activity from ca 2.8 mg N/min to about 51.6 ± 0.4 mg N/minin 48 h and a corresponding increase in amino-nitrogen content of ca2.0 ± 0.2 mg N 100 g dry matter (DM) to ca 18.5 ± 0.3 mg N/100g (DM) during the same period. Changes in the protease activity of thenatural process were gradual and increased from 3.0 mg N/min to 38.0 ±0.8 mg N/min after 5 days of fermentation. The maximum amino nitrogencontent of `ugba' produced by the starter cultures (18.5 ± 0.3 mgN/100 g DM) after 2 days was significantly (p < 0.05) higher than themaximum amino nitrogen content (12.5 ± 0.8 mg N/100 g DM), of `ugba'obtained by the natural process. `Ugba' produced by the starter cultureswere well accepted and compared favorably with the natural product.     

Retrogradation of waxy and normal corn starch gels by temperature cycling

Gelatinized waxy and normal corn starches at various concentrations (20–50%) in water were stored under temperature cycles of 4°C and 30°C (each for 1 day) up to 7 cycles or at a constant temperature of 4°C for 14 days to investigate the effects of temperature cycling on the retrogradation of both starches. Compared to starches stored only at 4°C, both starches stored under the 4/30°C temperature cycles exhibited smaller melting enthalpy for retrogradation (ΔH_r), higher onset temperature (T_o), and lower melting temperature range (T_r) regardless of the starch concentration tested. Fewer crystallites might be formed under the temperature cycles compared to the isothermal storage, but the crystallites formed under temperature cycling appeared more homogeneous than those under the isothermal storage. The effect of starch content on the retrogradation was greater when the starch gels were stored under cycled temperatures. The reduction in ΔH_r and the increase in conclusion temperature (T_c) by retrogradation under 4/30°C temperature cycles became more apparent when the starch concentration was lower (20 or 30%). Degree of retrogradation based on melting enthalpy was greater in normal corn starch than in waxy corn starch when starch content was low.     

High temperature storage of potato (Solanum tuberosum L.) for processing — a feasibility study

Tubers of three potato cultivars were stored at room temperature (20–39°C, 30–75% RH), under an insulated storage run on passive evaporative cooling (16–30°C, 70–90% RH) and a refrigerated storage (2–4°C, 90–95% RH) for 14 weeks and studied periodically for storage losses, reducing sugar content and dry matter percent of tubers, in order to explore the possibility of storing potatoes for processing at higher temperatures. Physiological losses in tubers remained less than 10% until 12 weeks of storage under evaporatively cooled storage. Reducing sugar contents increased by only 52.4–242.1% in tubers stored in evaporatively cooled storage as compared to 90.5–484.2% increase in tubers stored in refrigerated storage until 14 weeks. Potatoes stored in evaporatively cooled store were more suitable for processing into chips and french fries due to lower physiological losses and lower reducing sugar content of tubers.     

Physicochemical,microbiological and sensory changes in stored plantain chips

Plantain chips were produced from unripe plantain fruits.The chips were packed in polyethylene bags and stored at30 ± 2 ^°C for 1, 2 and 3 months, respectively.The storage stability of the chips was evaluated by analyzing periodically for changes in the physicochemical,microbiological and sensory characteristics. Protein andash contents of the chips did not change (p > 0.05) overtime. Fat decreased slightly (p > 0.05) over time. VitaminC decreased and was negatively correlated with storagetime (r = –95; p < 0.05). Peroxide value and microbialcount increased with storage (p < 0.05). Sensory scoresfor chips did not change (p > 0.05) at 2 months storage,but, thereafter, decreased (p < 0.05).     

Effects of seed treatments and storage on the changes in lipids of pearl millet meal

Lipids in pearl millet meal showed a rapid hydrolytic decomposition during storage. The magnitude of such degradation was influenced significantly by the nature of the storage container used, the temperature and heat treatments given to the seeds. The hydrolytic breakdown of lipids was significantly low in the meals stored in polyethylene bags, plastic boxes and under refrigerated (5±2 °C) conditions. Hot water blanching at 98 °C for 10 sec and dry heating of seeds at 100 °C for 120 min were found to be most effective in minimising the undesirable changes in lipids of the meal during storage.     

Control of brown rot of stone fruits by brief heated water immersion treatments

The effectiveness of brief (30 or 60 s) immersion in water at 24, 50, 55, 60, 65, or 70 °C was evaluated for the control of brown rot, caused by Monilinia fructicola, on California-grown peaches, nectarines, and plums. Inoculated fruits were treated and either stored at 20 °C for 5 days or at 0 °C and 95% RH for 30 days followed by 5 days at 20 °C to simulate commercial marketing conditions. Immersion in water at 55 °C for 60 s or at 60 °C for 30 or 60 s significantly reduced both decay incidence and severity among the remaining wounds that developed the disease. Water temperatures of 65 °C or higher were phytotoxic and caused moderate to severe surface injuries. Immersion in water at 60 °C for 60 s was effective for plums and it reduced the incidence of brown rot from more than 80% among control fruit to less than 2%. In nectarines, this treatment reduced decay incidence from 100 to less than 5% on fruit stored at 20 °C and from 73 to 28% on cold-stored fruit. Therefore, brief immersion in heated water can be an effective approach to manage postharvest brown rot of stone fruits, especially for the organic fruit industry.     

Effects of fruit dipping in hydrochloric acid then rinsing in water on fruit decay and browning of longan fruit

The objective of this study was to find alternative methods for the control of pericarp browning in longan fruits (Dimocarpus longan Lour.) cv. Daw in order to replace the use of sulfur dioxide (SO₂). Experiments were conducted by dipping fruits in 1.5 N HCl solution (pH 0.21) for 20 min followed by draining. The effects of subsequent rinsing in water were also investigated. Untreated fruits and SO₂ fumigated fruits were used as controls. Fruits from each treatment were then packaged in commercial perforated plastic baskets and stored at 3 ± 1 °C, 85% RH for 60 days. It was found that dipping the fruits in HCl controlled disease development compared with the untreated fruits. In addition, dipping the fruits in HCl as well as fumigating with SO₂ gave the best control of pericarp browning. After 5 days, the pericarp of untreated fruits became brown. Dipping fruits in HCl without rinsing reduced pericarp and juice pH and increased titratable acidity which lowered eating quality. Sensory analysis was carried out to determine aril color as well as appearance, firmness, flavor and taste. Dipping in 1.5 N HCl for 20 min and rinsing exhibited higher efficacy than dipping for 0, 10 or 15 min in controlling fruit decay and maintaining fruit color and eating qualities during 7 days storage at 25 °C following 45 days storage at 5 ± 1 °C. Therefore, dipping in 1.5 N HCl for 20 min, followed by rinsing in water can be considered for commercial application in extending shelf life, decreasing fruit decay and maintaining fruit quality of longan fruits.     

Effect of electrolyzed oxidizing water and continuous ozone exposure on the control of Penicillium digitatum on tangerine cv. ‘Sai Nam Pung’ during storage

The effect of electrolyzed oxidizing (EO) water in combination with ozone to control postharvest decay of tangerine cv. “Sai Num Pung” was investigated. The spore suspension containing 10⁵ conidia ml⁻¹ of Penicillium digitatum was prepared. EO water was generated by electrolysis of various concentrations of NaCl solution (5, 25, 50% and saturated NaCl). The spore suspension was inoculated into EO water and incubated at 27 °C for 1, 2, 4, 8 and 32 min. It was found that the EO water with saturated NaCl completely inhibited the spore germination of the fungus within 1 min. When the fruits inoculated with P. digitatum were washed in EO water at the same concentrations as previous experiment for 4, 8 and 16 min and stored at 5 °C for 18 days, it was found that immersion of the fruit in EO water for 8 min was the most effective to reduce disease incidences. Moreover, washing fruit in EO water and kept in a refrigerated chamber at 5 °C with continuous ozone exposure at a concentration of 200 mg l⁻¹ for 2 h day⁻¹ to extend storage life suppressed the disease incidence until 28 days. However, none of the treatments had any effect on the quality of fruit such as total soluble solids, titratable acidity, percent weight loss and peel color. Therefore EO water may be useful for surface sanitation and ozone has potential to control the recontamination of postharvest diseases in tangerine fruit in storage room.     

Quality and shelf life of calcium-enriched wholemeal bread stored in a modified atmosphere

Calcium-enriched wholemeal bread packed in a modified atmosphere (60% CO₂, 40% N₂), was examined for stability and microbiological changes throughout 32-day storage. The product was still acceptable after 24 days at 20 ± 1 °C. At this time no microbiological changes were observed; however, there was a continuous decline in sensory quality, mainly due to deterioration of the texture. Crumb hardness increased, whereas its springiness and cohesiveness decreased. These observations were accompanied by physical and chemical changes characterized by a steady increase in acidity and a sharp decrease in blue value, especially at the beginning of storage. The first microbiological changes occurred only after 27 days of storage and were due to the growth of moulds and amylase-negative Gram-positive cocci, cocci-bacillus or bacillus. The principal component analysis showed that nearly 86% of the variance in ten considered variables could be represented by two new variables: PC1, defined by eating quality and physicochemical attributes, and PC2 defined mainly by chewiness. Three groups of stored bread were identified on the score plot. The first group, fresh and 3-day stored bread, was characterized by low hardness and sourness; the second, bread stored from six to twenty days, scored lower for overall sensory quality, low springiness, cohesiveness and blue value; and the third group, the product during the final stages of storage, exhibited a clear increase in chewiness and hardness and showed the first indications of microbial deterioration.     

Acceptability and keeping quality of soymilk in Tanzania

Acceptability and keeping quality of two soymilk samples produced by hot water grinding and by presoaking in NaHCO₃ was determined in Morogoro town. In terms of flavour and taste the two samples were significantly different from cow's milk (p<0.05) but when vanilla was added (0.5 ml/l) the two samples were not significantly different from cow's milk. As estimated by using pH, titratable acidity and standard Plate Count, the milk samples could be kept at room temperature (25±2 °C) for up to 12 hours. To destroy 99% of the trypsin inhibitors in the soymilk samples, 45 minutes at 98 °C were needed for the alkaline presoaked milk while 75 minutes were needed for the plain water presoaked soymilk.     

Effects of roasting and storage on proteins and oil in peanut kernels

Peanut kernels, untreated or soaked in salt solution, were roasted at 160°C for 30 min in a hot air oven or oil roasted at 147°C for 2 min and, stored at 27°C and 5°C up to 150 days. The heat treatments significantly decreased methionine, tryptophan and in vitro protein digestibility (IVPD) and, increased the soluble proteins and acid value of kernel oil. Storage of heated peanuts caused an increase in water-soluble proteins, IVPD, acid value and saponification value and a decrease in methionine, tryptophan and iodine value. The oil roasting was found to be more detrimental to nutritional quality and storage stability of peanuts as compared to dry roasting. The storage of heated peanuts at 5°C was found to be beneficial in lowering the undesirable nutritional changes in the peanut kernels.     

Kenaf seed storage duration on germination,emergence, and yield

Kenaf (Hibiscus cannabinus L.) is a potential alternative crop being developed for fiber production. Because planting area varies dramatically from year to year, seed supplies may greatly exceed use so that the excess seed must be stored for one to several years. The objectives of this study were to determine the effect of seed storage duration at 10 °C on germination, vigor, emergence, and yield. Replicated trials were established at Starkville, MS in 1999 and 2000 to evaluate field emergence and biomass yield of kenaf seed from five ‘Everglades 41’ (‘E41’) harvest year seed lots stored at 10 °C in ambient relative humidity for up to 4 years. Germination of these same seed lots under standard (20–30 °C) and cool (20 °C) temperatures, and seed vigor was evaluated over time. Field emergence was the same for the different seed storage durations up to 4 years, but was directly affected by drought conditions for each planted year. Biomass yields ranged from 12.39 to 14.57 Mg ha⁻¹ in 1999 and 16.82 to 18.47 Mg ha⁻¹ in 2000, but were not different between storage durations. Seed germination remained greater than 80% regardless of storage duration. Electrolyte leakage, based on conductivity, was 38–50% less with freshly harvested seed than seed stored for 4 years at 10 °C. However, neither the conductivity nor accelerated aging test were reliable predictors of field emergence. Kenaf seed stored up to 4 years at 10 °C retained germination rates acceptable for commercial use. Neither field emergence nor biomass yield was affected by seed storage duration.     

Increased stored soybean dietary fibre concentration is positively correlated to testa darkening measured chromaticity

To assess efficacy of seed testa chromaticity indicator of dietary fibre changes in soybean (Glycine max L.), soybean samples were stored for zero (0 M), three months (3 M), six months (6 M) or nine months (9 M) at three moisture contents (MC) (9, 11 and 13%) and three temperatures (10, 20 and 30 °C). Stored soybean samples were analysed for seed testa colour and dietary fibre content. Extended storage (9 M) at high MC (13%) and temperature (30 °C) resulted in reduced chromaticity (C*ab) and L* (darkening) of the testa colour value by 6.7% and 4.7% respectively. Furthermore, storage time and elevated MC (13%) had the biggest effect on dietary fibre levels with insoluble and soluble dietary fibre increasing significantly up to 9 M of storage, by 4.90% and 15.09% respectively with a total dietary fibre increase of 4.62%. This effect was enhanced with increased storage time. Use of testa colour as an indicator of the effect of storage time and conditions on soybean dietary fibre levels contributed to understanding the related impact on the nutritional quality of soybean. This study elucidated the role of post-harvest storage time and conditions on soybean dietary fibre levels as related to chromaticity.     

Efficacy of composting infected plant residues in reducing the viability of Pepper mild mottle virus, Melon necrotic spot virus and its vector,the soil-borne fungus Olpidium bornovanus

Survival of Pepper mild mottle virus (PMMV) and Melon necrotic spot virus (MNSV) in diseased plant residues of pepper and melon, respectively, was studied in several experiments investigating drying and composting conducted in experimental heaps. The viability of the soil-borne fungus Olpidium bornovanus, the vector of MNSV, in infected melon root residues was also evaluated. Maximum temperatures in the heap reached 61.9–73.8 °C during composting processes. Drying of plant residues reduced the infectivity of MNSV whereas the infectivity of PMMV and O. bornovanus was unaffected by drying. Neither the virus nor the fungus was viable after composting. PMMV antigens where detected by serology after 30 and 60 days composting in the four experiments, but virus infectivity was detected only in one process after 30 days. Our results show that the use of composts using plant residues from PMMV and MNSV-infected crops as organic amendments in SE Spain do not appear to pose a risk of re-introducing pathogens to soil. Environmental conditions in that area are suitable for the adequate elimination of these pathogens from infected vegetable residues through composting even during winter.     

The Effects of Storage Temperature on the Staling of Wheat Flour Tortillas

Wheat flour tortillas (31·9% moisture) were stored at −60, −12, 0, 4, 22, and 35 °C to evaluate textural changes during staling. Subjective rollability and two-dimensional extensibility tests revealed that tortillas stored at ≥0 °C had increasing force, work and modulus of deformation values during storage. Tortillas stored at ≤−12 °C retained their fresh attributes over 25 days. Tortillas staled more as defined by rheological changes when stored at 22 °C than at 0, 4, or 35 °C. Optimum storage temperatures of wheat flour tortillas are ≤−12 °C while optimum staling temperatures are between 4 and 35 °C.     

Effect of domestic processing on total and extractable calcium and zinc content of Bathua ( Chenopodium album) and Fenugreek (Trigonella foenum graecum) leaves

Bathua (Chenopodium album) and fenugreek (Trigonella foenum graecum) stored in polyethylene bags and without packaging for 24 or 48 hours in a refrigerator at 5 or 30 ^°C in polyethylene bags. The fresh leaves were also dried (oven and sun); blanched (5, 10 or 15 min) and cooked in an open pan and a pressure cooker. The processed leaves were analyzed for total and extractable calcium and zinc content. The Ca and Zn content of these leaves varied from 970 to 2230 and 10.50 to 12.30 mg/100 g DM and the percentage HCl-extractability was 80.34 to 83.04 and 82.43 to 83.90, respectively. Non significant effects of drying and storage were observed on total Ca and Zn content and HCl-extractability while blanching and cooking resulted in significant improvement of HCl-extractability of these two minerals. Thus, cooking and blanching are good ways to improve the HCl-extractability of Ca and Zn.     

Effect of CIPC on Sprout Inhibition and Processing Quality of Potatoes Stored Under Traditional Storage Systems in India

Indigenous non-refrigerated methods like heaps and pits are used in India for short-term storage of potatoes (Solanum tuberosum L.) to avoid distress sale. Storing untreated potatoes generally results in high losses from sprouting, moisture loss and rotting. To reduce storage losses by inhibition of sprouting and to determine the suitability of stored potatoes for processing into crisps, a single spray application of a commercial formulation of 3-chlorophenyl carbamate (CIPC or chlorpropham) 50% a.i., (Oorja, United Phosphorus Limited, Mumbai, India) of CIPC (or chlorpropham) was tested on potatoes during storage from March to June under two traditional storage methods [heap (17–33 °C, 58–92% relative humidity (RH)) and pit (17–27 °C, 72–95% RH)] in 2 years [2005 up to 90 days of storage (DOS) and 2006 up to 105 DOS], using four cultivars and two rates of CIPC application (20 and 30 mg a.i. kg⁻¹ tubers). The two rates of application were comparably effective in reducing weight losses, sprouting and sprout growth in stored tubers, and the effect was more pronounced in pit storage than in heap storage. By contrast to untreated tubers, CIPC-treated potatoes remained turgid under the two storage methods and fetched market prices comparable to those for cold-stored (2–4 °C) potatoes after 105 days of storage. Reducing sugar concentrations in treated potatoes decreased during storage especially in 2006 when the initial reducing sugar concentration was higher than in 2005. Crisp colour improved only in 2005 after 90 DOS, but it deteriorated in 2006 during storage up to 105 DOS. Sucrose concentration increased tremendously during storage in 2 years. Only one cultivar (Kufri Chipsona-1) with low initial reducing sugar concentration and less sucrose accumulation during storage could produce acceptable colour crisps after storage in both years. The remaining three cultivars—with high initial reducing sugar concentration—were suitable for processing after storage in heap and pit in 2005, but not in 2006. Stored potatoes were safe for human consumption as the CIPC residue concentrations were far below the permissible level of 10 mg kg⁻¹ as prescribed by the European Union. Single spray application of CIPC (20 mg kg⁻¹ treatment) can effectively reduce storage losses in potatoes stored in traditional non-refrigerated methods of heap and pit and extend the storage life by 90 to 105 days.     

Effect of processing method on the quality of cowpea (Vigna unguiculata) flour for akara preparation

An indigenous food mixture containing rice flour, milk coprecipitate, sprouted green gram paste and tomato pulp (2: 1: 1: 1 w/w) was developed and called a RCGT food mixture. It was autoclaved (1.5 kg/cm², 15min, 121 °C), cooled and fermented with 2% liquid culture (containing 10⁶ cells/ml broth). Two types of fermentations were carried out i.e. one step single culture fermentation [L. casei or L. plantarum (37 °C, 24 hr.)] and sequential culture fermentation [S. boulardii (25 °C, 24 hr.) +L. casei (37 °C, 24 hr.)]; [S. boulardii (25 °C, 24 hr.) + L. plantarum (37 °C, 24 hr.)]. All fermentations drastically reduced the contents of phytic acid, polyphenols and trypsin inhibitor activity while significantly improving the in vitro digestibilities of starch and protein. Sequential culture fermentations brought about further changes compared to one step single culture fermentation.     

Chilean hazelnut butter,a new alternative for consumers

Four formulations of Chilean hazelnut butter were prepared containing Chilean hazelnut paste and 5%, 10%, 15% and 20% margarine. As the level of margarine was increased to 20%, the protein and crude fiber content decreased markedly, while those of moisture, crude fat and calories increased. After 90 days of storage, neither the samples stored at 5°C nor those stored at 15°C showed any objectionable effects both from the bacteriological and chemical point of view. Sensory analyses, including quality and acceptability studies, were performed on the various blends. Flavor, color and taste were improved by the addition of margarine to the butter formulas. It is concluded, therefore, that Chilean hazelnut butter represents a new and interesting alternative for human nourishment.