Biochemical and Nutritional Changes in Corn (Zea mays) during Storage at Three Temperatures

Two cultivars of corn (Zea mays), yellow and white were stored at 0°, 20° and 55°C for 7 months as whole grains and flours at 13-14% moisture. The changes in the soluble sugars and titratable acidity of the grains at 55°C and the titratable acidity of yellow corn grains stored at 0° and 20°C were significant (P < 0.05). Changes also occurred in the moisture content of all the samples and browning in the grains at 55°C (P < 0.05). The decrease in the Hunter L-values was greater in the grains than in the flour (P < 0.05). There were no significant differences in the pH, free amino nitrogen and protein digestibility (P > 0.05).     

Quality Changes in Stored Raw Grated Beetroots as Affected by Temperature and Packaging Film

The effects of atmospheric composition and temperature on quality of grated beetroots were analyzed. Beetroots ( Beta vulgaris L.) were washed, grated and packaged in trays wrapped with two films of different gas permeabilities. Trays were stored at 0°C or 4°C for a week and then transferred to 20°C. Changes in atmospheric composition, pigment content, pH, titratable acidity and production of exudate were monitored. Shelf-life of grated beetroots was 7 d at 0°C and 3 to 4 d at 4°C. There was a notable decrease in pigment content during storage.     

Functional, Nutritional, Mycological, and Akara-making Properties of Stored Cowpea Meal

ABSTRACT: Cowpea meal was packaged in high-density polyethylene bags, stored at -18 °C, 21 °C/55% RH, 37 °C/55% RH, and evaluated at 0, 4, 8, 12, 18, and 24 mo for functional, nutritional, mycological, and akara-making properties. Moisture content of meal varied no more than 0.5% and there were no marked changes in yeast and mold populations. Meal stored at -18 and 21 °C retained color, foam capacity, and akara-making quality for 24 mo. Overall, storage of cowpea meal at 37 °C was detrimental to its foaming characteristics, a key measure of performance in akara-making. A decline in protein solubility was also observed in the 37 °C samples.     

Application of response surface methodology for studying the quality characteristics of cowpea-fortified nixtamalized maize

Studies were conducted on the chemical and functional properties of fermented cowpea-fortified nixtamalized maize using response surface methodology. The central composite rotatable design for K=3 was used to study the combined effect of lime concentration (0–1%), moisture content (55–65%) and cowpea level (0–30%) on pH, titratable acidity, water absorption, protein and viscosity of fermented nixtamalized maize. Regression models were developed to predict the variables. The presence of lime and cowpea influenced the pH, titratable acidity, water absorption, protein content and the cooked paste viscosity of the fermented cowpea-fortified maize. The presence of lime during fermentation generally decreased titratable acidity, water absorption and cooked paste viscosity while the addition of cowpea increased most of the studied indices. Cowpea fortification can therefore be used to increase the nutritive value of nixtamalized maize with acceptable product quality characteristics.     

A comparison of the functional characteristics of wheat stored as grain with wheat stored in spike form

In this study, wheat grain and wheat spike with 12%, 14% and 16% moisture content were stored at 10, 20 and 30 °C for 0, 3, 6 and 9 months. After storage, wheat samples were investigated for hectolitre weight, gluten content, Zeleny sedimentation volume, enzyme activity, acidity, phytic acid and L colour value. Storage of wheat at different storage forms (spike and grain) and storage conditions showed considerable changes in grain quality. In general, the storage period of 3 months positively affected wheat quality. However, hectolitre weight, gluten, Zeleny sedimentation, enzyme activity, acidity and colour of wheat got worse at storage periods beyond 3 months. Hectolitre weight, wet and dry gluten, Zeleny sedimentation, phytic acid content and L Colour value of wheat stored in both spike and grain form significantly decreased during storage. However, the increase in grain moisture content, storage time and temperature resulted in significant increase in total titratable acidity and falling number values of wheat. Falling Number and phytic acid values of wheat stored in spike form were generally lower than wheat stored in grain form. Storage in spike form had a positive effect on especially wet gluten content of wheat stored at non-optimal storage conditions such as high grain moisture content and high temperature. Wet gluten of wheat stored in spike form was higher than that of wheat stored grain form after storage at 30 °C for 6 and 9 months. Wheat stored in spike form is more resistant than wheat stored in grain form against adverse storage conditions such as high moisture content and temperature and longer storage time.     

Effect of Hot Water Treatments on Quality of Highbush Blueberries

ABSTRACT:  Highbush blueberries, cv 'Burlington', were treated with 22, 45, 50, or 60 °C water for 15 or 30 s along with an untreated control. Fruit were then stored for 0, 1, 2, or 4 wk at 0 °C and 2 or 9 d at 20 °C prior to evaluation of microbial population and fruit quality. After 4 wk of storage, the hot water treatment at 60 °C resulted in 92% marketable berries, followed by 90% at 50 °C, 88% at 45 °C, and 83% at 22 °C compared with 76% in untreated controls. Decay incidence was reduced to 0.6%, 1.2%, 1.4%, or 2.8% with 60, 50, 45, or 22 °C water treatments, respectively, compared with 5.1% in controls following 4 wk at 0 °C and 2 d at 20 °C. After an additional 7 d at 20 °C, decay in fruit treated at 60 °C for 15 or 30 s remained at 1.8% and 0.4%, respectively, compared to 37.4% in controls. Weight loss of berries treated with hot water was 0.4% against 3.8% in controls, and shriveled and split berries were also reduced compared to controls ( P < 0.001). Aerobic plate count and yeast and mold count were reduced by 0.45 to 0.7 log at 60 °C for 30 s. Botrytis cinerea and Colletotrichum sp. were the dominant fungal pathogens causing decay of Burlington blueberries during storage. Hot water treatments also immediately induced an increase in ethanol and reduced fruit titratable acidity and soluble solids content, but had no significant effect on fruit firmness, pH, or most flavor volatile concentrations.     

Effect of carbon dioxide on improving the keeping quality of raw milk

Fresh cows' milk samples were treated with CO₂ to give a calculated CO₂ content of 77mM. The treated samples as well as the control were stored at 7° and 20 ± 5°C for three days and analysed periodically. The increase in the total count as well as the counts of psychrotrophic, lactic acid and coliform bacteria during storage at 7°C was found to be inhibited by the addition of CO₂. The treated samples had higher titratable acidity and lower pH values than the controls but satisfied the clot-on-boiling test. The keeping quality of cooled milk can therefore be improved by the addition of CO₂.     

Changes in the free -NH2, free -CO2H and titratable acidity of meat proteins

The 2, 4, 6-trinitrobenzene sulphonic acid (TNBS) spectrophotometric assay and formol titration were used to measure changes in free -NH₂ and free -CO₂H respectively, in meat proteins dissolved in 3% sodium dodecyl sulphate (SDS). Changes in the titratable acidity of the meats was also determined. The free -NH₂ groups were found to decrease markedly with cooking while -CO₂H remained relatively constant. Intermediate moisture beef ( Longissimus dorsi ) processed and stored at 38°C showed the free groups increasing for up to 8 weeks' storage due to proteolysis, followed later by a sharp fall due to cross-linking. But titratable acidity of the IM beef samples continued to rise with storage.     

Effect of sonication on orange juice quality parameters during storage

Freshly squeezed orange juice was sonicated at various amplitude levels (40%, 70%, 100%), treatment times (2, 6 and 10 min) at a constant frequency of 20 kHz. Samples were stored for periods of up to 30 days at 10 °C. The combined effect of amplitude level, treatment time and storage period on pH, ^oBrix, titratable acidity, colour values ( L* , a* , b* ), non-enzymatic browning (NEB), cloud value and ascorbic acid content were investigated. Second order polynomial models were employed to investigate the effect of independent variables. No significant differences ( P <  0.05) in ^oBrix and titratable acidity were observed. Significant changes were observed in juice pH and colour values. During storage NEB increased while both cloud value and ascorbic acid content decreased. Predictive models developed for colour values, cloud value, NEB and ascorbic acid content were highly significant and were closely correlated to experimental data. Degradation mechanisms are proposed for the key quality parameters.     

Effect of 1-Methylcyclopropene on the Quality of Fresh-cut Apple Slices

ABSTRACT: The objective of this project was to treat fresh-cut apple slices with the ethylene inhibitor 1-methylcyclopropene (1-MCP) to retard ethylene-induced deterioration and senescence and to prolong the shelf life of such products. Intact Braeburn and Pacific Rose apples were treated at different times with 1-MCP, cut, and stored at 0 °C. Samples were analyzed initially and then weekly for ethylene, respiration, flesh firmness, tissue color, titratable acidity, and soluble solids content during 5 wk of storage. 1-MCP treatment was effective in reducing ethylene production, respiration, and loss of firmness and color of slices when applied to whole apples directly after harvest. Total sugar and acidity levels were not affected significantly.     

The effects of different incubation temperatures on the acetaldehyde content and viable bacteria counts of bio-yogurt made from ewe's milk

Yogurt and bio-yogurt were manufactured from ewe's milk using a starter culture and a probiotic culture. Incubation was carried out at 37°C and 42°C until pH 4.6 was reached and the yogurts were stored at 4 +1°C for 14 days. Analysis after 1, 7 and 14 days showed that incubation temperature and storage time significantly influenced overall properties of the samples. During the storage, whey separation and pH decreased, but titratable acidity, lactic acid and volatile fatty acid contents increased. Viable bacterial counts in all bio-yogurts were above 10⁷ cfu g⁻¹ at the end of storage.     

Maintaining the quality of sugarcane juice with blanching and ascorbic acid

The physicochemical changes in fresh sugarcane juice stored at 10 °C were studied by determining juice yield, color, reducing sugar, titratable acidity, viscosity, pH, polyphenol oxidase (PPO), sucrose neutral invertase (SNI) and total microbial count. Results showed that blanching of stems before squeezing effectively prevented degreening and/or browning, and reduced activities of PPO and SNI in fresh sugarcane juice. Added ascorbic acid delayed the increase of reducing sugar, titratable acidity, viscosity and total microbial count, and also prevented degreening and/or browning with reduced PPO and SNI activities in fresh sugarcane juice during storage. Addition of 0.1% ascorbic acid seemed to be more effective than blanching of sugarcane stems, and was able to maintain the quality of fresh sugarcane juice for up to 5 days at 10 °C. Deterioration of fresh sugarcane juice was demonstrated as a rapid increase of titratable acidity and viscosity with a obvious browning.     

Flavor, Aroma, and Compositional Changes in Strawberry Juice Concentrate Stored at 20° C

Strawberry juice concentrate (68°Brix) was stored at 20°C for 0–6 days. Samples were analyzed for changes in taste, aroma and color degradation, and these changes were related to composition change. Astringent taste, musty/moldy and pungent aromas and brown color developed rapidly over 6 days. This decrease in quality was accompanied by CO₂ production and a decrease in free amino acids, while reducing sugar and titratable acidity concentrations remained stable.     

Reduction of chilling injury in ripe Alphonso mango fruit in cold storage by temperature conditioning

The influence of ripening temperature and cold conditioning of pre-climacteric fruits on the incidence of chilling injury (CI) in ripe mango fruits cv. Alphonso during refrigerated storage was investigated. Fruits previously held and ripened at tropical ambient temperature (AT, 27–34°C) developed CI (skin staining or browning) when ripe fruits were subsequently stored at 5, 10, or 15°C for shelf-life extension. Fruits held and ripened at 20°C1°C, RH 85–90% showed little evidence of CI when subsequently stored at 5 or 10°C up to 14 days. Chilling injury in ripe mangoes was also avoided by holding pre-climacteric fruits for a minimum period of 30 days at 10°C and then ripening them at 27–34°C. The quality of the ripe mangoes remained good during cold storage for 7 days and were acceptable until 10–14 days with minimal changes in texture, flesh colour, carotenoids, total soluble solids, titratable acids and ascorbic acid. Shelf-life of ripe mangoes can thus be extended under refrigeration by pre-storage conditioning.     

Effect of calcium on the storage life of oro (Antiaris africana)

The effects of calcium on the ascorbic acid, chlorophyll, titratable acidity and texture (firmness) of stored oro (Antiaris africana (Mill)) friuits (average weight 100 g ) were studied. Three groups of the fruits were dipped in 20 g litre^?1, 40 g litre^?1 CaCl₂ solutions and deionised water respectively for I0 min. The fourth group, which was untreated, served as the control and was also packaged in heat-sealed cellophane bags. The fruits were displaced and stored at ambient temperature (28 ± 2°C). The calciumtreated fruits which kept better were firmer and had a slight colour change (chlorophyll) which also produced a progressive increase in ascorbic acid level during storage. The titratable acidity of the fruits did not fluctuate as signijcantly as that of the untreated (control) fruits.     

Sugar metabolism and involvement of enzymes in sugarcane (Saccharum officinarum L.) stems during storage

Sugarcane (Saccharum officinarum L. cv. Badila) was harvested at the mature stage and stored at 2, 10, and 20 °C for 30, 90, and 120 days, respectively. Metabolic changes in the contents of sucrose and reducing sugar in relation to the activities of soluble acid invertase (SAI), neutral invertase (NI) and sucrose-phosphate synthase (SPS), in sugarcane juice, were studied. Extractable juice, sucrose and vitamin C declined significantly with increasing storage temperatures, while respiration rate increased. There was a rapid increase in titratable acidity during storage, with a more rapid rate at higher temperatures. A sharp increase in reducing sugar was observed within 20 days at 20 °C and 70 days at 10 °C, followed by a rapid decrease. Both SAI and NI activities showed a sharp increase within 15 days at 20 °C, followed by a rapid decrease, while a moderate increase occurred within 40–60 days at 10 °C. Slight increases were observed in SPS activity within 20 days at 20 °C and 50 days at 10 °C. Enzyme activities remained steady or underwent a small change in canes stored at 2 °C. Enzyme activities were significantly correlated with reducing sugar content.     

Effect of Initial Acidity of Plain Yogurt on Acidity Changes during Refrigerated Storage

The relationship between initial acidity of plain yogurt and the changes in this acidity during refrigerated storage has been investigated. Yogurt samples with initial pH 4.5 ± 0.1, pH 4.2 ± 0.1 and pH 3.9 ± 0.1 were prepared under laboratory conditions and stored at 4°C and 7°C for 3 wk. pH and titratable acidity were monitored weekly. Results indicated that samples with the lowest initial acidity (high pH) showed the highest increase in acidity during refrigerated storage (pH 4.59–4.15). Samples with high initial acidity (low pH) remained fairly stable (pH 3.82–3.77). Acidity changes during refrigerated storage were more pronounced at 7°C compared to 4°C (pH 4.59–4.27 at 4°C; pH 4.59–4.15 at 7°C). Changes in acidity were maximal for the first week and minimal thereafter.     

Impact of controlled atmosphere on the stability of Dhakki dates

The dates equilibrated at water activity (a_w) of 0.52, 0.58 and 0.75 were stored at 40 °C for 4 months under the controlled atmosphere of nitrogen, oxygen and air. The samples were evaluated monthly for darkening, pH, and titratable acidity. The study indicates that the darkening and titratable acidity increased whereas the pH declined gradually during the storage. The change in quality appeared to be a function of storage atmosphere and water activity. Among all the investigated options, the sample stored under the nitrogen atmosphere at lowest water activity (0.52a_w) showed the greatest stability.     

Effect of storage conditions on the chemical attributes of Ogbomoso mango juice

Mango juices were extracted from Ogbomoso variety using the method of Brekke et al. (1972). Mango juices were packaged in polyethylene films, polyethylene tetraphthalate (PET or plastic) bottles and transparent glass bottles and stored at 6 °C, 26 °C and 34 °C. Percentage ascorbic acid loss, browning index, titratable acidity, pH and soluble solids were evaluated at 2-week intervals for 8 weeks. Percentage ascorbic acid loss, non-enzymatic browning and titratable acidity increased with storage time in all packaging materials. However, pH decreased with storage time and soluble solids remained constant. Higher percentage ascorbic acid loss, browning index and titratable acidity occurred in juices packaged in polyethylene film, than in PET and glass bottles. Percentage ascorbic acid, browning index and pH increased with increased storage temperature. However, titratable acidity decreased with increased storage temperature and soluble solids remained constant throughout the period of storage.     

TEMPERATURE ACCLIMATION OF ATLANTIC COD (GADUS MORHUA) AND ITS INFLUENCE ON FREEZING POINT AND BIOCHEMICAL DAMAGE OF POSTMORTEM MUSCLE DURING STORAGE AT 0° and -3°C

The freezing point of muscle fluid from Newfoundland Atlantic cod held at ambient sea water temperature was as low as - 1.30°C in March and as high as - 0.80°C in July. Muscle fluid from cod held live at 0°C for 3 weeks had a freezing point of - 1.02°C in contrast to a muscle fluid freezing point of - 0.90°C for cod acclimated at 10°C prior to sacrifice. Muscle fluid from cold acclimated cod exhibited 0.40°C thermal hysteresis indicating freezing point depression was influenced by antifreeze substances. The following indices of deterioration were measured in muscle sections stored at 0°C or - 3°C for 21 days: extractable protein (EP), free drip (FD), extracellular area (EA), trimethylamineoxide (TMAO), trimethylamine (TMA), dimethylamine (DMA), free amino acids (AA), and pH. Muscle sections at the anterior end of fillets, from myotomes 9–20, prepared using aseptic technique and treated with antibiotic showed less evidence of biochemical deterioration: (a) when stored at - 3°C compared to 0°C with respect to EP, AA, EA; (b) when prepared from fish acclimated at 0°C compared to at 10°C and stored at 0°C or - 3°C with respect to EP, EA, FD, AA. Negligible changes in pH, TMA and DMA occurred during 21 days storage at either temperature. TMAO decreased more during storage at-3°C than at 0°C.