Treatment of Potato Processing Wastewater with Coagulating and Polymeric Flocculating Agents

Reduction of wastewater strength in abrasive-peeled, lye-peeled, and steam-peeled potato processing wastewater using 4 inorganic salts and 11 polymers was investigated. Treatment of wastewater with 150 mg/ L FeCl₃ 6H₂O + 20 mg/L Purifloc Anionic Polymer #23 aided in coagulation and flocculation of suspended solids of effluent from abrasive-peeled potatoes including greater than 90% reduction in chemical oxygen demand (COD), total suspended solids (TSS) and turbidity. Treatment with 300 mg/L CaCl₂+ 25 mg/L Purifloc #23 reduced COD and TSS levels in wastewater from lye-peeled potato by 69% and 76%, respectively. In steam-peeled effluent, 350 mg/L CaCl₂+ 25 mg/L Nalco 7122 reduced TSS by 90% and COD by 60%. Waste strength of effluent from processing potatoes can be substantially reduced by treating with coagulating and flocculating agents before discharging into municipal or other treatment systems.     

A COMPARISON OF FRUIT OF HIGHBUSH AND RABBITEYE BLUEBERRY CULTIVARS1

In 1986, 1988 and 1989, fruit from highbush blueberry (Vaccinium corymbosum L., cvs Collins, Bluecrop, and Herbert) and rabbiteye blueberry (V. ashei Reade, cvs Climax, Tifblue, and Menditoo) grown at the same location were compared for size, raw product quality, storage, and sensory attributes. Compared with rabbiteye blueberry fruit, fruit of highbush cvs were generally larger in size, volume, and surface area and higher in titratable acidity, higher Hunter color attributes of ‘L’, ‘a’, ‘b’, and chroma, protein, P, Ca, Mg, Mn, Fe, Cu, B (dry wt. basis), and higher in decay and water loss after 3 weeks storage at 7 C. Rabbiteye fruit, compared with highbush fruit, were generally higher in pulp pH, percent soluble solids, percent dry matter, seed weight per fruit, weight per seed, fruit height/width ratio, periderm dry weight per fruit, periderm wt. per surface area (in mg/cm²), sugar:acid ratio, firmness (as shear), and in sensory seediness. Fruit soluble solids, dry matter, hue, titratable acidity, pulp pH, and firmness of both species were influenced by weather (years).     

Prediction of Sensory Profile of Mango Using Textural Attributes During Ripening

Mango is an important commercial fruit and is marketed based on their colour, firmness and taste. These sensory parameters vary with individual mango and person involved in testing. There is little or no information available on the instrumental estimation of these sensory attributes. The present study, therefore, was conducted to correlate sensory and instrumental textural attributes to explore the possibility of predicting them for seven major cultivars of mango influenced by harvesting dates and ripening period (10 days). In general, the textural property of peel, pulp and fruit decreased while sensory attributes increased during fruit ripening. Sensory qualities like taste, flavour and overall acceptability were significantly affected by harvesting date, cultivar and ripening period. Harvesting time and cultivars, however, did not influence the fruit appearance. Among textural attributes, peel firmness was closely associated with all the sensory parameters indicating that textural parameters could be useful to predict sensory profile of mango cultivars during their ripening. Cultivar-specific variations were observed while evaluating various equations (linear/polynomial/exponential/logarithmic/power) for correlating their textural and sensory attributes. Polynomial equation was found to be the best fit (highest coefficient of determination, R ²) for prediction of sensory quality using textural properties of majority of mango cultivars. All cultivars under study except Alphonso collected from Maharashtra showed R ² value above 0.911 which indicated potentiality of the fitted equations for the prediction of sensory attributes using textural characteristics of mango.     

Isolation of ursolic acid from apple peels by high speed counter-current chromatography

Cuticular waxes of four varieties of Malus domestica were investigated regarding their content of ursolic acid. Peels from Fuji, Gala, Smith and Granny Smith apples were extracted with chloroform, ethyl acetate and/or ethanol. The crude extracts were purified by high speed counter-current chromatography (HSCCC), by using mobile and stationary phases derived from the two-phase solvent system composed by n-hexane:ethyl acetate:methanol:water in the proportion of 10:5:2.5:1. The phase proportions and the relative distribution of ursolic acid between the two-phases were optimized by TLC and optical densitometry, by comparison with an authentic sample of ursolic acid. The amount of ursolic acid present in the extracts as well as the characterization of the isolated compound were made by high resolution gas chromatography coupled to mass spectrometry (GC–MS), ¹³C nuclear magnetic resonance (¹³C NMR), Infrared; and by comparing thin layer chromatography and flame ionization detection gas chromatography (GC–FID) patterns with the commercial sample. The average content of ursolic acid of 0.8 mg/cm² in the peel (around 50 mg per medium sized fruit with a surface area of 50–70 cm²) was found in the Fuji and Smith varieties, whereas 0.5 mg/cm² and 0.2 mg/cm² were the amounts calculated for Granny Smith and Gala, respectively. The HSCCC technique was shown to be a good method to purify free ursolic acid from apple peels and could represent a new technological tool to be developed to exploit industrially this source of product.     

Effects of variety, ripening condition and ripening stage on the quality of sulphite-free dried mango slices

The influence of cultivar and fruit ripeness on sensory properties and all-trans-β-carotene contents of dried mango slices was evaluated. Different ripeness stages, quantitatively defined by a ripening index (RPI), were generated from a single lot per cultivar by subjecting mature-green mangoes of the cultivars ‘Nam Dokmai’, ‘Kaew’, and ‘Chok Anan’ to different postharvest ripening regimes. Fruits were ripened for 2 and 3 days at 24±2 °C/45–60% relative humidity (RH) and 33±2 °C/50–70% RH, with application of calcium carbide (CaC₂) or 2-chloroethylphosphonic acid (CEPA, Ride^®) beside the control, terminating postharvest ripening when fruit firmness allowed proper peeling and slicing. After ripening, fruits were washed, peeled, sliced and subsequently dried in a conventional tray dryer at 70 °C for 8–10 h, until the water activity of the dried fruits was below 0.65. Mangoes cv. ‘Kaew’, followed by ‘Chok Anan’, were more suitable for drying than cv. ‘Nam Dokmai’ because of superior all-trans-β-carotene contents of the products. Maximum β-carotene contents of dried mango slices from cvs. ‘Chok Anan’ and ‘Kaew’ corresponded to retinol equivalents of 333–383 and 483–905 per 100 g of edible portion (dry weight), meeting daily mean requirements of vitamin A for adults according to FAO/WHO. Similar to the fresh fruit, exponential rise of all-trans-β-carotene contents with increasing fruit ripeness was also observed for the dried products of cvs. ‘Nam Dokmai’ and ‘Chok Anan’. Consistently, accelerated ripening at 33 °C, instead of 24 °C, resulted in higher all-trans-β-carotene contents of dried fruits. Both good sensory acceptance and cultivar-specific maximum all-trans-β-carotene contents of 13–16 and 20–23 mg kg^?1 usually characterised the products of ‘Nam Dokmai’ and ‘Chok Anan’ fruits with RPI levels between 3 and 4. Conversely, fruits cv. ‘Kaew’ of RPI levels above 6 generally yielded products inferior in sensory acceptance and β-carotene contents, while superior product quality was found at higher RPI levels than for the other two cultivars.     

Comparative study of six pear cultivars in terms of their phenolic and vitamin C contents and antioxidant capacity

The main phenolic compounds in six pear cultivars were identified and quantified using high‐performance liquid chromatography/diode array detection (HPLC/DAD) and HPLC/electrospray ionisation mass spectrometry (HPLC/ESIMS). Major quantitative differences were found in the phenolic profiles. The peel contained higher concentrations of chlorogenic acid, flavonols and arbutin than the flesh, where only chlorogenic acid was detected. Total phenolics ranged from 1235 to 2005 mg kg^?1 in the peel and from 28 to 81 mg k g^?1 in the flesh. Ascorbic acid and dehydroascorbic acid were detected in the peel, whereas only dehydroascorbic acid was present in the flesh. The ranges of vitamin C content were from 116 to 228 mg kg^?1 in the peel and from 28 to 53 mg kg^?1 in the flesh. The antioxidant capacity was correlated with the content of chlorogenic acid (r = 0.46), while ascorbic acid made only a small contribution to the total antioxidant capacity of the fruit. Copyright © 2003 Society of Chemical Industry     

Regulation of the levels of health promoting compounds: lupeol,mangiferin and phenolic acids in the pulp and peel of mango fruit: a review

There is a demand for feasible methodologies that can increase/maintain the levels of health-promoting phytochemicals in horticultural produce, due to strong evidence that these compounds can reduce risk of chronic diseases. Mango (Mangifera indica L.), ranks fifth among the most cultivated fruit crops in the world, is naturally rich in phytochemicals such as lupeol, mangiferin and phenolic acids (e.g. gallic acid, chlorogenic acid and vanillic acid). Yet, there is still much scope for up-regulating the levels of these compounds in mango fruit through manipulation of different preharvest and postharvest practices that affect their biosynthesis and degradation. The process of ripening, harvest maturity, physical and chemical elicitor treatments such as low temperature stress, methyl jasmonate (MeJA), salicylic acid (SA) and nitric oxide (NO) and the availability of enzyme cofactors (Mg²⁺, Mn²⁺ and Fe²⁺) required in terpenoid biosynthesis were identified as potential determinants of the concentration of health-promoting compounds in mango fruit. The effectiveness of these preharvest and postharvest approaches in regulating the levels of lupeol, mangiferin and phenolic acids in the pulp and peel of mango fruit will be discussed. In general spray application of 0.2% iron(II) sulphate (FeSO₄) 30 days before harvest, harvest at sprung stage, storage of mature green fruit at 5 °C for 12 days prior to ripening, fumigation of mature green fruit with 10⁻⁵ mol L⁻¹ and/or 10⁻⁴ mol L⁻¹ MeJA for 24 h or 20 and/or 40 µL L⁻¹ NO for 2 h upregulate the levels of lupeol, mangiferin and phenolic acids in pulp and peel of ripe mango fruit. © 2019 Society of Chemical Industry     

Effect of foliar sprays containing calcium,magnesium and titanium on peach (Prunus persica L) fruit quality

Sprays containing Ca²⁺, Mg²⁺ or Ti⁴⁺ were applied to peach trees in several combinations. Effects of treatments on the commercial quality of fruits, especially focused on improving their mechanical properties, are discussed. All treatments containing titanium increased tree performance (branch elongation, flowering and fruit set intensities) and fruit size. At harvest, fruits from Ti‐treated trees showed improved resistance to compression and penetration, as well as a decrease in weight loss during postharvest storage. A similar response was obtained for external colour, though all treatments seemed to delay somewhat the apparent ripening status. Nevertheless, fruits from Ti‐treated trees showed better behaviour in the evolution of colour parameters during storage than did control fruits. Titanium application showed significant increases in iron, copper and zinc concentrations in the peel and calcium concentration in the peel and flesh. This improvement in calcium absorption is explained as a consequence of the beneficial effect of titanium on the absorption, translocation and assimilation processes. Copyright © 2004 Society of Chemical Industry     

Contribution of amino acids to strawberry fruit quality and their relevance as stress indicators under NaCl salinity

Strawberry cvs Korona and Elsanta, differing in their sensitivity to salt stress, were exposed to 0, 40, or 80 mM NaCl in the root medium from the end of April to mid-August. Although fruits of both cultivars contained comparable amounts of Na⁺ and Cl⁻, fruit quality was more impaired in cv. Elsanta, as indicated by the larger reductions of fruit size and sugar/acid ratios. Malondialdehyde levels started to rise significantly at 40 mM NaCl in the more sensitive cv. Elsanta, but at 80 mM in cv. Korona. Total amino acid levels, especially contents of essential amino acids, rose significantly in both cvs. Salt stress also increased contents of free proline, asparagine, and glutamine. Their increases may contribute to osmotic adjustment. The results of the present study favour the interpretation that elevated levels of proline, asparagine and glutamine are indicative of salt stress damage.     

Total phenolic content and antioxidant capacity of extracts obtained from six important fruit residues

The extracts from kinnow peel, kinnow seeds, litchi pericarp, litchi seeds, grape seeds, and banana peel were screened for total phenolic content (TPC), trolox equivalent antioxidant capacity (TEAC), 1,1 diphenyl-2-picryl hydrazyl (DPPH) radical scavenging activity, as well as reducing power. Kinnow peel extract exhibited the highest reducing power, TEAC, and DPPH free radical scavenging activity, whereas, the phenolic content of 37.4 mg GAE/g-dw was highest for grape seed extract. Banana peel extract with a low TPC showed the lowest reducing power, TEAC as well as DPPH free radical scavenging activity among the fruit residue extracts examined in the present study. Correlation analysis between the reducing power and DPPH radical scavenging ability; reducing power and ABTS radical scavenging activity; and ABTS and DPPH radical scavenging abilities showed a high degree of correlation (r² = 0.85-0.91). However, r² of 0.36, 0.66, and 0.49 between TPC and DPPH radical scavenging activity; TPC and reducing power; and TPC and ABTS radical scavenging ability, respectively, indicated that some non-phenolic compounds also contributed to the total antioxidant activity in fruit residue extracts examined in this study. To the best of our knowledge, this is the first paper presenting comprehensive data on TPC, reducing power, and antioxidant activity for the six fruit residues. This study demonstrated that kinnow peel, litchi pericarp, litchi seeds, and grape seeds, can serve as potential sources of antioxidants for use in food and pharmaceutical industry.     

TEXTURAL AND SENSORY ATTRIBUTES OF CURRIED RAW JACK FRUIT, FRIED AND PRESSURE COOKED

Studies were conducted to improve the texture and sensory qualities of raw jack fruit. Diced tender jack fruit was subjected to steam cooking (1 kg cm^-2 for 20 min) and oil frying at 150 ± 30C for 5 min and 180 ± 20C for 5 min, respectively. Minced mutton at 5% (w/w) of the jack fruit dice was incorporated into the curried recipe prepared from dice fried in oil at 150C to impart mutton flavor and tested for texture. The firmness of fried dice increased significantly as measured by peak force of 11.06 and 11.49 kg. cm^-2 compared to 0.33 kg. cm^-2 of steamcooked dice. Further, the sensory evaluation for texture and flavor of the samples in the curried recipe also revealed that the fry-treated samples (at 150 ± 30C) were better in quality than steam-cooked samples. The frying treatment of raw jack fruit dice increased the oil content of the dice (8.26% on FWB) compared to 0.6% in steamed dice. However, the treatment did not affect salt pick up.     

EVALUATION OF PROCESSING TOMATOES FROM TWO CONSECUTIVE GROWING SEASONS: QUALITY ATTRIBUTES, PEELABILITY AND YIELD

Peelability is an important quality parameter in the selection of tomato cultivars (cvs.) for whole peeled and dice processing. Six processing tomato cvs. were evaluated in two consecutive years to examine the effects of cv., maturity and physical attributes on peelability and yield. Physical attributes of the raw tomatoes (size, weight, pericarp wall thickness, color) and processed paste quality (pH, titratable acidity, soluble solids, Bostwick consistency, serum viscosity, color) were determined. Large variations in physical attributes and paste quality were observed in selected tomato cvs. and maturities. In general, most of the attributes indicative of paste quality were more desirable at the less mature (e.g., pink) stage and declined with maturity. Statistical analysis suggests that there were significant differences in percentage of peeled tomatoes, peel index, and yields of whole peeled and diced tomatoes between two consecutive growing years.     

Quality Characteristics of Four Mulberry (Morus sp) Cultivars in the Area of Chania,Greece

Four cultivars of mulberry, Morus sp (cvs Mavromournia (red-fruited), Mavri (black-fruited), Rodini (purple-fruited) and Aspri (white-fruited)) were harvested at three stages of harvest maturity (immature, mature and fully mature). The fruit were evaluated for fresh weight, firmness, total soluble solids, titratable acidity and anthocyanin content and composition. Mavromournia mulberries significantly differed compared to the other cultivars in all quality characteristics and especially in titratable acidity and anthocyanin content. Cyanidin-3-grucorutinoside is responsible for about 60% of the fruit coloration. Mavromournia mulberries are fruit of excellent quality characteristics and have a great market potential as fresh or processed product. © 1997 SCI.     

Bioactive components in forced sweet cherry fruit (Prunus avium L.), antioxidative capacity and allergenic potential as dependent on cultivation under cover

Five early maturing varieties of Prunus avium L. on dwarfing rootstock were forced at Bonn, Germany in spring under transparent plastic cover without additional heating to ripen at a time before field-grown German fruit become available, with better fruit quality than imported sweet cherries; trees grown outside without cover served as control. The cover reduced the incident radiation by up to 54% PAR, UV by up to 22% UV-A and UV-B up to 2% and increased day temperature indoors. Fruit were as firm in the early varieties grown under cover as those in the field and slightly softer than in the late harvesting cultivars. Sugar content was slightly less in four of the five varieties; no differences in acidity and sugar/acid ratio as a taste indicator were found. Fruits were up to 3 mm larger when grown under cover in cvs. ‘Burlat’ and ‘Souvenir’, but no differences were observed in cvs. ‘Earlise’ and ‘Prime Giant’. Fruit of three cultivars, ‘Burlat’, ‘Samba’ and ‘Prime Giant’ can be classified as premium quality with 28 mm–30 mm diameter, when grown under cover. Overall, all cherry fruit were of the market, i.e. consumer- preferred, dark red colouration in line with enhanced anthocyanin contents. In two cultivars, the cover induced healthier fruit. Antioxidative capacity was larger in cv. ‘Samba’, while ascorbic acid (Vitamin C) was increased in cv. ‘Souvenir’; phenols were enhanced in all cultivars and attributed to heat stress. Allergenic protein (Pru av 1) in cherry fruits of both cultivation types were below the detection level at harvest time, indicating that cultivation under cover had no adverse effects on this particular health component.Overall, forcing successfully resulted in 2 weeks earlier ripening, thereby providing the first fresh and healthy (low allergen, high phenolic compounds and high anthocyanin) German cherries of high fruit quality on the market in spring.     

Apples Nutraceutic Properties Evaluation Through a Visible and Near-Infrared Portable System

Non-destructive and rapid tools are required for predicting the optimum harvest window and for monitoring fruit quality during postharvest period. This study tested a portable, experimental visible/near-infrared (vis/NIR) spectrophotometer, more versatile and handy than traditional vis/NIR instruments, to measure phytonutrients active in human health and important in fruit storability. Parameters determining sensorial and quality properties of the fruit were also analyzed. The vis/NIR measurement was carried out in field using apples of “Golden Delicious” and “Stark Red Delicious” on tree. Calibration models were developed using PLS regression based on second derivative spectra. For “Golden Delicious” apple, the cross-validation R ² for soluble solids content (SSC), chlorophyll, titratable acidity (TA), flesh firmness, total phenols, carotenoids, and ascorbic acid were 0.72, 0.86, 0.52, 0.44, 0.09, 0.77, and 0.50, respectively. The corresponding RMSECV were 0.78 °Brix, 0.50 nmol/cm², 0.59 g/L, 6.08 N, 0.10 mg/g, 0.08 nmol/cm², and 0.83 mg/100 g, respectively. For “Stark Red Delicious” similar calibration statistics were found for SSC, TA, flesh firmness, chlorophyll, and ascorbic acid content. A better calibration performance was achieved for total phenols, while for carotenoids it was less accurate. Cross-validation R ² for “Stark Red Delicious” total anthocyanins, total flavonoids, and non-anthocyanic flavonoids were 0.67, 0.86, and 0.77, respectively. The corresponding RMSECV were 0.12, 0.14, and 0.15 mg/g, respectively. It was concluded that the portable vis/NIR instrument performed similarly to bench top or portable vis/NIR instruments reported in the literature.     

Effect of pre‐ripening chilling temperatures on ripening,shelf life and quality of bananas treated with 1‐methylcyclopropene

Ethylene production, shelf life and fruit quality of Cavendish bananas (cv. Williams), held at different pre‐ripening storage temperatures (5 °C, 10 °C or 15 °C) prior to ethylene and/or 1‐methylcyclopropene (1‐MCP) application, were determined and compared. Levels of ethylene production during ripening were highest for control fruit that had been stored at 5 °C followed by 10 °C and then 15 °C. 1‐MCP treatment (at 300 nL L^?1) had no effect on ethylene production of fruit that had been stored at 10 °C by day 10 of storage, but ethylene production was significantly higher for fruit that had been stored at 15 °C and lower for those stored at 5 °C before 1‐MCP treatment. 1‐MCP also increased shelf life to a greater extent when applied to fruit that had been stored at 10 °C or 15 °C. Even though 1‐MCP had no significant effect on under peel chilling injury, it increased discolouration significantly, regardless of storage temperature. Firmness of 1‐MCP‐treated fruit decreased significantly compared to the control when fruit were held at 5 °C or 15 °C prior to ripening (and 1‐MCP application) but had no effect on fruit stored at 10 °C before ripening. These results indicate that pre‐ripening storage temperature affects ripening, shelf life and quality in both ethylene and 1‐MCP‐treated bananas.     

Effect of drying and storage time on the physico-chemical properties of mango leathers

Fruit leathers are made by drying a very thin layer of fruit puree to obtain a chewy product. The objective of this work was to minimise the drying time required to produce mango leathers with no preservatives and no sugar added, and to evaluate their acceptance and storage stability. Mango puree was spread on Petri dishes and oven‐dried according to a central composite design with two independent variables: drying temperature (60–80 °C) and puree load (0.4–0.6 g cm^?2). The minimum drying time (120 min) resulted from drying a puree load of 0.5 g cm^?2 at 80 °C. The product was well accepted, especially in terms of flavour. The mango leathers were packed in polypropylene buckets and stored at 25 °C. The combination between low water activity (0.62) and low pH (3.8) allowed the product to be microbiologically stable for at least 6 months, without the need for chemical preservatives.     

Evaluation of the Amazonian fruit Ambelania acida: Chemical and nutritional studies

Ambelania acida is native to the Amazon region, with few published studies of its fruits. We examined the proximate composition of its fruits, including minerals, fatty acids, volatile organic compounds (VOCs), as well as its antioxidant capacity. The protein contents (2.61%) of the pulp and seeds (13.6%) were higher than observed in other taxa of the family or in other tropical fruits. Peel and pulp showed high contents of potassium, calcium, and magnesium, and the potassium content in the pulp was 1125 mg/100 g. The peel had higher contents of total phenolics, tannins, and ortho-diphenols than the pulp, as well as better antioxidant activity as evidenced by 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH), Ferric Reducing Antioxidant Power (FRAP), and Fe²⁺ chelating activity assays. GC-MS analyses identified 42 VOCs in the peel and pulp, with more than 90% being classified as terpenes. Eleven types of fatty acids were identified in the lipid fractions of the peel, pulp, and seeds. Linoleic acid, an essential fatty acid for humans, was the principal fatty acid in the edible portion of the fruit, therefore, evidencing its nutritionally significant profile for the fruits when considering the relationship among polyunsaturated, saturated, and monounsaturated fatty acids. The information gathered here indicates that this native fruit is a healthy food source and its cultivation and consumption should be stimulated.     

Can coloured hailnets improve taste (sugar, sugar: acid ratio), consumer appeal (colouration) and nutritional value (anthocyanin, vitamin C) of apple fruit?

Envisaged photo-selective effects, as reported for kiwi and grapevine, of white, red-white, red-black and green-black hailnets were investigated in apple cvs ‘Pinova’ and ‘Fuji Kiku 8’ near Bonn, Germany in 2007; uncovered trees served as control. Light transmission of green or red hailnets peaked at 490-610 nm (green) or above 610 nm (red-orange), was reduced by ca. 12% or 14% by white or red-white, respectively, and by 18% or 20% by red-black and green-black hailnets. Air temperature under coloured hailnets was decreased by an averaged 1.3 °C and humidity increased by 2-5% rh. The peel of apples under coloured hailnets contained more chlorophyll (NDVIndex), but 4-5-fold less anthocyanin (NAIndex). The greater sugar (up to 0.7 g/100 g TSS) and acid content, i.e. the better fruit quality and consistent taste (sugar: acid ratio), the firmer fruit (by up to 0.6 or 0.8 g/100 g TSS in ‘Fuji’ or ‘Pinova’) with advanced starch breakdown and improved colouration (NAI) under the red-white and white hailnets was attributed to more light than under the red-black and green-black hailnets; hence, white hailnets appear a compromise to obtain good quality and healthy fruit and still protect the plants against sunburn and adverse weather conditions such as hail.     

Effects of controlled atmosphere storage on respiratory metabolism of apple fruit tissue

The effects of CO₂ and O₂ concentrations commonly used in fruit storage upon various respiratory processes in apple fruit tissue have been investigated. In manometric experiments 10% CO₂ inhibited CO₂ release from succinate supplied to peel discs by over 50%; CO₂ release from malate was inhibited at high substrate concentrations, while CO₂ release from pyruvate was not affected. High CO₂ concentrations also inhibited ¹⁴CO₂ release from succinate 1,4-¹⁴C and succinate 2,3-¹⁴C supplied to peel discs. It is concluded that succinate dehydrogenase is the respiratory enzyme most affected by CO₂ concentration. Oxygen uptake was found to be 50% inhibited at ambient concentrations of 0.5% O₂ for cortical tissue and 5% O₂ for peel tissue. It is concluded that cytochrome oxidase is responsible for O₂ uptake in peel and cortical tissue. The apparent low affinity for O₂ in peel respiration may be due to limited O₂ diffusion through the tissue. It is concluded that O₂ uptake by the bulk of the apple is not directly affected by O₂ concentrations employed in fruit storage.