Domain: Healthcare — Nutrition & Dietetics
Target concept: Apply ascorbic acid solution to cut fruits to reduce surface discoloration

Video generation prompt: Cut an apple into two halves; immerse one half in a vitamin C solution and the other half in water, then place each half, cut side up, on differently colored plates under the same experimental conditions.

Evaluation guide:
(i) Target concept: Enzymatic browning inhibition via antioxidant-mediated redox cycling and pH-dependent enzyme suppression.
Minimum mechanism: Apple tissue must be freshly cut (exposing polyphenols and PPO to O₂); vitamin C solution must be present at effective concentration to reduce quinones and acidify surface; browning requires aerobic exposure post-immersion; differential outcome depends on sustained chemical protection, not barrier formation.
(ii)Storyline: [Frame 0–2] Fresh apple whole → [Frame 3–4] Knife cuts apple cleanly into two symmetrical halves → [Frame 5–6] Left half lowered into clear liquid in labeled container (vitamin C), right half lowered into clear liquid in unlabeled container (water) → [Frame 7–8] Halves lifted, excess liquid drips, cut surfaces fully exposed → [Frame 9–10] Halves placed simultaneously cut-side up on adjacent plates (e.g., red left, blue right) → [Ongoing] Water half develops uniform brown hue on cut surface; vitamin C half retains original pale cream color, all under fixed frontal viewpoint, consistent lighting, no occlusion.

Manual:
Experimental Procedure
1. Cut an apple into two equal halves.
2. Immerse one half in vitamin C solution, the other in water.
3. Remove both halves and place them cut-side up on two differently colored plates.
Observation of Experimental Phenomena
The apple half immersed in water browns visibly over time; the half immersed in vitamin C solution remains light-colored with no browning.
Summary of Experimental Principles
Ascorbic acid (vitamin C) acts as an antioxidant that inhibits enzymatic browning by reducing o-quinones back to colorless diphenols and lowering pH to inhibit polyphenol oxidase.

Prompt Grounding rubric:
level_1: No apple is shown, or no cutting action appears, or only one half is ever visible, or no liquid immersion is shown, or the two plates aren't visible, or the plates are the same color, or a cut side faces down instead of up, or neither half is placed on a plate at all.
level_2: The apple is cut, but only one half appears; or both halves appear but only one is immersed in any liquid; or both are immersed but in the same liquid (e.g., both in water); or the plates are present but share the same color; or at least one half sits cut-side down or sideways.
level_3: The apple is cut into two clearly distinct halves; both halves sit cut-side up on two differently colored plates; one half was immersed in a liquid before placement and the other half in a different liquid, but neither liquid is identifiable as vitamin C solution versus plain water (both look clear, with no label or other visual cue distinguishing them).
level_4: On top of everything already covered at score 3: the two liquids are visually distinguishable by a labeled versus unlabeled container, different container shapes, or a contextual cue such as a dissolving tablet in one container; however, the immersion itself is not fully shown (e.g., only the post-immersion placement appears, with no visible submersion or liquid contact).
level_5: On top of everything already covered at score 4: the immersion is explicitly shown: each half is visibly submerged in its own liquid for at least one continuous frame with the whole cut surface in contact with the liquid, followed by its removal and placement cut-side up on its differently colored plate, all within a single fixed-viewpoint shot with no cuts or edits.

Scientific and Causal Correctness rubric:
level_1: No color difference ever appears between the two apple halves; OR both halves discolor identically and at the same rate; OR the vitamin-C-soaked half discolors as fast as or faster than the water-soaked half; OR discoloration appears before immersion or without any exposure to air.
level_2: Discoloration appears on at least one half, but the timing is backward (e.g., the water half stays paler for longer); OR discoloration appears only on the vitamin-C half; OR both halves brown identically with no contrast; OR discoloration appears while a half is still submerged, which oxidation in open air cannot explain.
level_3: Both apple halves sit cut-side up on their differently colored plates; discoloration appears on the water half but not on the vitamin-C half within the clip; OR discoloration appears on both but is clearly milder on the vitamin-C half, though no pre-immersion baseline color is shown, so the amount of relative change can't be confirmed.
level_4: On top of everything already covered at score 3: both halves start out with the same fresh-cut pale yellow-cream color at the first frame after placement, with no prior browning; discoloration then develops only on the water half over the course of the clip while the vitamin-C half keeps its original color, though the two halves' timing isn't quite in step (e.g., the water half starts browning well before the clip's midpoint, breaking the expected side-by-side pace).
level_5: On top of everything already covered at score 4: discoloration begins at the same point in time on both halves from the same starting color, then visibly progresses faster and further on the water half while the vitamin-C half stays unchanged, with no reversal, fading, or artificial color shift such as a desaturation filter.

Spatiotemporal Consistency rubric:
level_1: An apple half jumps to a different spot in frame with no motion carrying it there; either plate swaps to a different color mid-clip; the vitamin C or water container is simply gone from a later frame with no pour or removal action shown taking it away; the room's light switches abruptly, e.g., daylight to indoor tungsten light in under a second; or an apple half stretches, melts, or turns on its own axis with nothing touching it.
level_2: An apple half blinks in and out of frame; a plate's edge visibly warps or skews out of its normal round shape; the immersion skips a step (e.g., a half sits above the liquid in one frame and is fully submerged two frames later with no contact frame in between); the shadow beneath a plate swaps to its opposite side with no change to the room's lighting; or a cut surface rotates more than roughly 15 degrees with nothing shown causing it.
level_3: Both apple halves, both containers, and both plates stay visible and stay in roughly the same part of the frame throughout, with nothing swapped out or removed from view partway through; the room's brightness doesn't swing up and down; each object's shadow stays under that same object rather than jumping to another one; the cutting, immersing, and placing all look physically ordinary, but one plate drifts sideways slightly (roughly more than a tenth of its own width) between being placed and being observed, or a half wobbles a little without visibly resting on anything.
level_4: On top of everything already covered at score 3: neither plate drifts, wobbles, or changes apparent size or angle once placed; the two differently colored plates keep the same side-by-side layout from placement to the end of the clip; the shadow cast by each apple half at the moment it is lifted from its liquid and placed on its plate falls on the same side as it did during the immersion step moments earlier, for both the vitamin-C half and the water half; however, one frame shows a brief see-through or ghosting glitch on an apple surface or a plate edge.
level_5: On top of everything already covered at score 4: there is no flicker, ghosting, or ripple-edge artifact on either apple half or plate at any point; neither half ever appears to float above its plate or pass through another object; the plate meant to sit nearer the camera never swaps places with the one behind it without an actual moving cause; and the edges of both apple halves and both plates stay clean and steady rather than turning jagged or flickering at normal viewing scale.