The core argument of the review is that conventional food processing—built on manual labor and rudimentary mechanical automation—has simply become too slow, too imprecise, and too data-starved to meet modern demands for speed and accuracy. Quality decisions, the authors note, have long rested on subjective human judgment, introducing uncertainty at every stage from raw produce screening to final shelf inspection. Deep learning, a subfield of machine learning that uses multi-layered neural networks to automatically extract features from raw data, offers a way out. Its strength lies in hierarchical feature learning: convolutional neural networks (CNNs) can learn low-, mid-, and high-level representations directly from images or spectra, bypassing the fragile hand-crafted features—color histograms, texture descriptors—that limited earlier machine vision systems. Weight sharing and pooling operations also keep parameter counts manageable, reducing overfitting and improving generalization across the notoriously diverse and complex matrices that food presents.

At the raw-material stage, the documented performance gains are striking. A ResNet50 classifier trained to recognize the typical appearance of healthy tomatoes achieved an average precision of 94.6 percent, distinguishing stem scars from genuine surface defects. Data-augmented CNNs pushed the classification of defective versus healthy lemons to 100 percent accuracy, while an AlexNet-based system sorted hazelnuts into five defect categories—cracks, holes, marks, cuts, and soundness—with 99 percent accuracy. For defects hidden beneath the skin, the review highlights the power of pairing deep learning with hyperspectral imaging: three-dimensional CNNs coupled to hyperspectral data detected bruises in oranges with accuracy above 90 percent, substantially outperforming their two-dimensional counterparts, which fell short of 83 percent. A 3D-CNN applied to Nanfeng mandarins using competitive adaptive re-weighted sampling for wavelength selection reached 97.27 percent accuracy in identifying external defects. Because food safety and freshness depend heavily on internal chemistry as well as surface appearance, the authors argue that this fusion of spectral information and deep learning represents the most promising route to rapid, non-destructive, whole-fruit evaluation.

Maturity and freshness assessment show equally impressive results, often by combining modalities. An Inception V3 model classified hawthorn fruits as immature, mature, or overripe with perfect accuracy after the training set was augmented from 600 to 3,000 images. For kiwifruit, whose exterior betrays little about ripeness, researchers merged visible–near-infrared spectroscopy and acoustic vibration measurements with a one-dimensional CNN to estimate soluble solids content and hardness at 93.08 and 92.31 percent accuracy, respectively. In the freshness domain, fluorescence sensor arrays read by a SqueezeNet model detected meat spoilage with 98.17 percent accuracy in five to seven seconds, while an attention-based LSTM network processing spatially offset Raman images of shrimp achieved a coefficient of determination of 0.93 for freshness prediction end-to-end. For cold-chain logistics, a CNN-LSTM hybrid tracking egg quality under real storage conditions cut prediction error from an RMSE of 6.62 to 2.02 relative to conventional random-forest and artificial neural network models—a difference the authors note translates directly into reduced waste and foodborne illness risk.

Inside the processing plant itself, deep learning is enabling something the industry has long sought: real-time quality prediction that lets operators adjust temperature, pressure, and timing on the fly. During fluidized-bed drying of green peas, a Unet-Xception system performed semantic segmentation of pea images with a mean intersection over union of 0.9464, tracking color, texture, and size continuously. A hybrid CNN-BiLSTM-Squeeze-and-Excitation model monitoring red-date hot-air drying predicted soluble solids, acidity, moisture, and hardness with prediction coefficients between 0.919 and 0.975, outperforming partial least squares regression and support vector machines. Fermentation is another success story: LSTM networks fed ultrasonic and temperature data predicted beer alcohol content with an R² of 0.952, a 2D-CNN calibration strategy cut kombucha prediction errors by up to 72 percent, and an InceptionResNetV2 model classified sugar crystallization types at 90.1 percent accuracy with roughly half a second of inference latency per image—fast enough for line-side control. Packaging integrity, too, has been automated, with Faster R-CNN achieving 99.25 percent accuracy on aseptic package seals and a DenseNet161-based system inspecting thermoformed packs at 99.93 percent accuracy with false-negative rates below 0.07 percent.

The safety chapter of the review is perhaps the most consequential for public health. Deep learning models paired with short-wave infrared hyperspectral imaging detected pesticide residues on leek leaves at up to 98.5 percent accuracy, and a CNN-BiGRU-self-attention model identified four pesticide types on apple surfaces with an F1 score of 0.9630. Acrylamide, the carcinogenic compound that forms during high-temperature frying, was identified in potato chips by a transfer-learned MobileNetV2 in 3.33 seconds per sample at 99.12 percent accuracy. Against aflatoxin B1—a Class I carcinogen that resists degradation until 280 degrees Celsius—a sub-pixel CNN regression model quantified contamination in peanuts with an R² of 0.8898, while a Dual-aspect Attention Spatial-spectral Transformer detected Aspergillus flavus infection at 99.40 percent accuracy and correctly pinpointed contamination timing at 100 percent. Pathogen detection has advanced in parallel: CNNs classified six common foodborne bacteria with 90 to 100 percent accuracy, and a portable Raman instrument coupled to a 1D-CNN achieved essentially perfect classification of single-species bacterial cultures captured on 3D nanostructured swabs. Adulteration screening rounds out the safety portfolio, with ConvLSTM models detecting vegetable-oil adulteration in camellia oil at 100 percent classification accuracy and a fine-tuned ResNet identifying horse-fat adulteration perfectly from infrared spectra.

Beyond safety, the review documents deep learning’s growing role in predicting what consumers actually experience. Mask R-CNN systems predicted pineapple taste from external images in agreement with trained sensory panels, and hybrid CNN-LSTM models coupled to Raman spectroscopy predicted pork batter gel strength with correlation coefficients approaching unity. The most futuristic work connects neural decoding to flavor: EEG-based multiscale residual networks can distinguish the five basic tastes, a frequency-band attention network identified the odors of eight food products with 98.92 percent accuracy, and a Transformer-based model called EEG-MambaFusionNet predicted the aroma perception of grilled lamb skewers at 92.5 percent accuracy by fusing brain signals, temporal sensory data, and gas chromatography–ion mobility spectrometry. Nutritional composition is also within reach—Transformer models predicted protein content in lentils from near-infrared spectra with an R² of 0.977, and attention-enhanced architectures predicted oil, protein, and starch in coix seeds and carbohydrate in bean flour without destroying a single sample. Even shelf life, long estimated by slow microbiological assays, is now being forecast by backpropagation neural networks for products ranging from Antarctic krill sauce to ready-to-eat salads and dried tofu, with relative errors frequently below 10 percent.

The authors are careful, however, to temper enthusiasm with a candid assessment of the field’s bottlenecks. Deep learning models are data-hungry, and high-quality labeled food data are expensive, seasonal, and heterogeneous. Distribution shift—driven by cultivar differences, climate-driven variability in raw materials, camera and lighting differences between factories, and sensor calibration drift—remains the central technical hurdle, degrading accuracy whenever models cross factories, batches, or harvest seasons. The black-box nature of deep networks also limits regulatory acceptance in safety-critical contexts, and the computational demands of Transformers and deep CNN ensembles strain the hardware budgets of small and medium-sized enterprises. Perhaps most fundamentally, deep learning models do not encode the physicochemical laws governing food processes, meaning they cannot be trusted to extrapolate reliably to conditions outside their training domain.

The path forward, the review concludes, lies less in ever-bigger networks than in smarter integration. The authors call for physics-informed neural networks and hybrid mechanistic–data-driven models that respect underlying food science, explainable AI that regulators can audit, federated learning frameworks that let factories share knowledge without surrendering proprietary data, and lightweight architectures deployable at the edge on the factory floor. Multi-modal sensing platforms that fuse hyperspectral imaging, Raman spectroscopy, electronic noses, and machine vision into unified architectures are expected to define the next generation of process control, while reinforcement learning may eventually allow production lines to autonomously optimize drying temperature, fermentation duration, and packaging parameters in closed loop. The implications extend beyond profit: accurate shelf-life prediction could support dynamic expiration labeling and cold-chain optimization, cutting food waste and carbon emissions alike. What began as a promising pattern-recognition tool, the authors argue, is maturing into a cornerstone technology for safe, sustainable, and intelligent food production—provided the field can close the gap between laboratory prototypes and industrial reality.

The system is built around the biology of climacteric fruits. Unlike non-climacteric fruits, climacteric fruits undergo a characteristic ripening process associated with a rise in respiration and increased ethylene production. Ethylene binds to receptors in plant tissues and activates signaling pathways that alter gene expression, accelerating processes such as starch breakdown, softening, pigment changes and the development of aroma compounds. Bananas and kiwifruit are both strongly influenced by this hormone, although their visible and biochemical changes occur at different rates. Ethylene can accumulate inside a sealed or semi-sealed package, making it a potentially useful marker of ripening progression. It is not, however, a complete definition of spoilage: microbial contamination, bruising, water loss and temperature history can also determine whether fruit is safe or desirable to eat. The researchers therefore treat ethylene as a measurable indicator of freshness-related change rather than as a universal substitute for every quality test. Their objective was to determine whether a chemical sensor could respond consistently enough to support an automated image-based classification system.

Potassium permanganate, or KMnO₄, provides the chemical component of the detector. The compound is a powerful oxidizing agent that can react with ethylene, effectively removing the gas while undergoing a change that can be expressed through the indicator’s color. In an intelligent package, this chemistry transforms a gas concentration that cannot be seen by the naked eye into an optical signal. The researchers tested indicators containing 0.1, 0.5 and 1.0 percent KMnO₄ by weight per volume. The different concentrations were intended to reveal how sensor formulation affects sensitivity and how closely the visual response tracks the ethylene released by the fruit. Too little reactive material could produce a weak or delayed signal, while a higher concentration might alter the response range or timing. Among the formulations examined, the 0.5 percent indicator showed the highest correlation between ethylene concentration and color change. That result identifies a practical middle ground for the tested conditions, although it does not establish that the same concentration will be optimal for every fruit, package design, temperature or storage duration.

For the experiments, bananas and kiwifruit were stored at 25 degrees Celsius for 10 days in polypropylene pouches containing the indicator. The setup created a controlled package environment in which ethylene released during ripening could interact with the sensing material. Polypropylene is commonly used in food packaging because it is lightweight and provides a controllable barrier to moisture and gases, but the precise exchange of oxygen, carbon dioxide and ethylene depends on pouch thickness, sealing and design. Those variables matter because gas accumulation determines how quickly a sensor changes. Temperature also has a major influence on fruit metabolism and chemical reaction rates; storage at 25 degrees Celsius represents a warm, accelerated ripening condition rather than every situation encountered during refrigerated transport or household storage. Across the storage period, the researchers compared the indicator’s optical response with ethylene-related freshness changes. The strongest relationship occurred with the 0.5 percent formulation, suggesting that the indicator could encode ripening information in a form suitable for image analysis. The study did not present the indicator as a preservation treatment, and it should not be confused with a packet that extends shelf life.

The second half of the innovation is software. The team trained a ResNet50 deep-learning model to interpret images of the indicator and predict the freshness status of the fruit. ResNet50 is a convolutional neural network architecture designed for visual recognition. Its defining feature is the use of residual connections, which allow information and gradients to pass through many layers more effectively during training. Rather than relying only on manually selected measurements such as average hue or brightness, a deep neural network can learn complex visual patterns from labeled examples, including subtle combinations of color distribution, intensity and spatial variation. In this application, the model does not directly smell the fruit or measure ethylene with a conventional gas analyzer. It infers the fruit’s freshness category from the image of a chemical response that has already integrated information about the package atmosphere. That distinction is important: the model’s performance depends on the quality and consistency of the indicator, the lighting conditions, the camera and the training data. A visually impressive prediction is only as reliable as the chain of chemical, photographic and statistical measurements behind it.

According to the researchers, the ResNet50 model achieved high accuracy when predicting the freshness of both bananas and kiwifruit, and the trained system was incorporated into a mobile application for real-time analysis. A user can photograph the indicator in the fruit package, after which the application processes the image and returns a freshness assessment. Mobile imaging offers a potentially powerful advantage over laboratory instrumentation because smartphones are already widely available and can perform sophisticated computer-vision tasks. The application could also standardize interpretation, reducing dependence on a person’s ability to judge small color differences. For retailers, such a system might support inventory rotation by identifying packages approaching a ripening threshold. For households, it could make freshness information more visible before food is discarded. For researchers and manufacturers, the same platform could be adapted to other colorimetric sensors. Yet “high accuracy” in a controlled study is not equivalent to perfect performance in the real world. Lighting, reflections from plastic, condensation, camera differences and background colors can all shift the apparent signal. Robust deployment would require testing across phones, packaging formats, cultivars and storage environments.

The work is part of a broader movement toward intelligent food packaging, in which labels do more than display a sell-by date. Conventional dates are assigned using expected storage conditions and conservative estimates, but they do not necessarily reflect the actual history of an individual package. A sensor that responds to biological or chemical changes could provide more dynamic information. Similar research has explored colorimetric systems for meat and other foods, while potassium permanganate has also been studied as an ethylene scavenger because removing ethylene can slow ripening. Combining sensing and machine learning adds a layer of interpretation: instead of asking a person to compare a label with a color chart, an algorithm can evaluate the image against patterns learned from experimental data. The result could be a more flexible freshness label, but it also raises practical questions about cost, disposal, chemical containment and regulatory requirements. Potassium permanganate must remain isolated from direct food contact, and an indicator designed for packaging would need to be stable, safe and resistant to accidental leakage. The study demonstrates a detection concept, not a final commercial package.

The researchers’ findings are especially relevant because food waste often occurs at the boundary between uncertainty and caution. Fresh produce can be discarded because shoppers or retailers cannot determine how much useful life remains, even when the fruit is still edible. A rapid indicator could help distinguish ripening from more advanced deterioration, potentially improving decisions throughout distribution. But the distinction between freshness and safety remains essential. Ethylene accumulation is closely tied to ripening in climacteric fruit, whereas harmful microorganisms may grow without producing a matching indicator response. A package that receives a favorable AI assessment should not override basic food-safety practices, and a negative assessment would not by itself identify the cause of deterioration. The next steps for this technology will likely involve broader validation under fluctuating temperatures, varying humidity and realistic transportation conditions, as well as tests involving different ripeness stages and fruit varieties. Researchers will also need to report detailed model-performance measures and establish how the application behaves when images fall outside its training set. For now, the study shows how plant hormones, oxidation chemistry, computer vision and mobile software can be combined into a single window on the hidden life of packaged fruit.